CdSe/CdS/ZnS quantum dot (QD) modified C60 nanorods were performed by the liquid–liquid interfacial precipitation method. Transmission electron microscopy and scanning electron microscopy were used to characterize the hybrid C60 structure and found that the CdSe/CdS/ZnS QDs were attached on the surface of C60 nanorods. UV–vis absorption spectroscopy, surface photovoltage spectroscopy (SPS), and steady-state and transient spectra photoluminescence (PL) were used to investigate the nanorods’ optoelectronic properties. The CdSe/CdS/ZnS QD PL quench, decreasing lifetime, and enhanced SPS response were observed for the hybrid QDs/C60 nanorod films. The charge transport property of a single C60 nanorod modified by CdSe/CdS/ZnS QDs was also investigated for photocurrent occurrence. It is considered that the photoinduced charge transfers from CdSe/CdS/ZnS QDs to C60 nanorods by tunneling through the oleylamine ligand. The hybrid QDs/C60 nanorod will be a good system for adjusting the interaction and the ability of charge transportation between the QDs and C60 by ligand exchange. The in situ preparation method for the hybrid QD/C60 nanorod films has high yield at room temperature.

Cu2ZnSn(S,Se)4 (CZTSSe) absorber layers are fabricated by co-electrodeposited Cu–Zn–Sn–S (CZTS) precursors followed by selenization. In order to complex the Cu ions and shift its reduction potential to more negative, trisodium citrate is applied as the complexing agent during the co-electrodeposition. After the co-electrodeposition, CZTS precursors are preliminary annealed at 280 °C in order to improve the homogeneity by intermixing of the elements. The influences of selenization temperatures on the chemical compositions, crystal phases, optical properties and photovoltaic device performances are also systematically investigated by X-ray energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), Raman spectroscopy, UV–vis absorption spectroscopy, and J–V measurements. EDS results reveal that the CZTSSe absorber layers are all in a Cu-poor and Zn-rich nature, which is beneficial for fabricating cells with high efficiency. It is found that the crystalline quality and morphology of the CZTSSe absorber can be greatly improved by post-selenization at 550 °C. Photovoltaic devices are fabricated with standard soda-lime glass (SLG)/Mo/CZTSSe/CdS/i-ZnO/ITO/Ag grid structures. Champion cell demonstrates 2.81% efficiency based on the optimized CZTSSe absorber. These results validate co-electrodeposition as a promising strategy for developing earth-abundant thin film solar cells at low-cost.

In this work, CuInGa alloy precursor films are fabricated by co-sputtering of CuIn and CuGa targets simultaneously. After selenization in a tube-type rapid thermal annealing system under a Se atmosphere, the Cu(In, Ga)Se2 (CIGS) absorber layers are obtained. Standard soda lime glass (SLG)/Mo/CIGS/CdS/i-ZnO/ITO/Ag grid structural solar cells are fabricated based on the selenized CIGS absorbers. The influences of selenization temperatures on the composition, crystallinity, and device performances are systematically investigated by x-ray energy dispersive spectroscopy, x-ray diffraction, Raman spectroscopy, and the current density–voltage (J–V) measurement. It is found that the elemental ratio of Cu/(In + Ga) strongly depends on the selenization temperatures. Because of the appropriate elemental ratio, a 9.92% conversion efficiency is reached for the CIGS absorber selenized at 560°C. After the additional optimization by pre-annealing treatment at 280°C before the selenization, a highest conversion efficiency of 11.19% with a open-circuit (Voc) of 456 mV, a short-circuit (Jsc) of 40.357 mA/cm2 and a fill factor of 60.82% without antireflection coating has been achieved. Above 13% efficiency improvement was achievable. Our experimental findings presented in this work demonstrate that the post-selenization of co-sputtered CuIn and CuGa precursor is a promising way to fabricate high quality CIGS absorbers.

•Patterned honeycomb-like ZnO cavities fabricated by NSL.•Light harvesting through scattering and coupling of the incident light.•Omnidirectional behavior in a wide incident angle range.•10.6% enhancement in the energy conversion efficiency is achieved.A novel idea was presented by using patterned honeycomb-like ZnO cavities to enhance the light harvesting of Cu(In,Ga)Se2 (CIGS) thin film solar cells in a broadband wavelength range. Large-scale patterned honeycomb-like ZnO cavities were fabricated through the versatile colloidal lithograhpy technique combined with the subsquent hydrothermal growth reaction. The growth mechanism was proposed based on the structural evolution of the patterned ZnO cavities. By introducing the patterned honeycomb-like ZnO cavities into CIGS solar cells, the performances of the device can be remarkabley improved due to the enhanced light harvesting. Photovoltaic device with a standard soda lime glass (SLG)/Mo/CIGS/CdS/i-ZnO/AZO/ZnO cavities/Ag grid structure exhibited a maximum power conversion efficiency of 11.4% under the standard AM 1.5 global illumination with a light intensity of 100 mW/cm2. An improvement of over 9.0% in the short-circuit photocurrent density and a 10.6% enhancement in the energy conversion efficiency were achieved compared with the standard reference device without ZnO cavities. More importantly, the device with patterned ZnO cavities exhibited omnidirectional behavior within a wide incident angle range. The enhancement of light harvesting is originating from the novel “negative” configuration of patterned ZnO cavities, which can realize high-efficient light trapping by multiple scattering and light coupling.Download high-res image (406KB)Download full-size image

•Modulation the heterogeneous and homogeneous reaction in CdS deposition.•Optimization of CdS buffer layer by post-annealing.•A highest conversion efficiency of 12.57% was achieved.•A promising strategy for high efficient CIGS solar cells was reported.An optimization of CdS chemical deposition process is presented in order to fabricate high quality CdS buffer layer for high-performance CIGS thin film solar cells. It is found that the heterogeneous and homogeneous reaction can be regulated conveniently by changing the concentration of cadmium acetate. No obvious large CdS particles on the surface of CdS film can be observed due to the dominant heterogeneous reaction and suppressed homogeneous precipitation under the suitable concentration of cadmium acetate. The device with CdS buffer layer deposited at 0.052 M cadmium acetate shows the best efficiency of 11.42%. The performance of the device can be further improved by post-annealing treatment in air. An improved champion efficiency of 12.57% is achieved at the annealing temperature of 180 °C.Download high-res image (283KB)Download full-size image

Since the introduction of inorganic ZnO nanoparticles as an electron transport layer (ETL) material, the device performance of colloidal quantum dot light-emitting diodes (QLEDs) has been rapidly improved. Although there have been rapid advances in luminance, efficiency and lifetime, device performance is still limited by balanced electron/hole injection into the quantum dot layer. In this study, solution-processed Zn1−xMgxO (ZMO) films with tunable bandgaps were designed as an ETL for high performance QLEDs. It was found that the band gap of ZMO broadened as the energy level varied with increasing Mg concentration. As a consequence, the energy barrier between the Al cathode and ZMO ETL was tuned to balance the electron/hole injection towards a better device performance. The luminance intensity increased from 20 229 to 36 685 cd m−2, while the current efficiencies increased from 3.74 to 13.73 cd A−1, and the power efficiencies increased from 4.65 to 12.94 lm W−1 with a 0.05% Mg doping ratio. Particularly, the optimized device based on ZMO exhibited an enhanced external quantum efficiency (EQE) of 9.46%, which was 3.67-fold compared with that of pure ZnO nanoparticles (2.58%). The proposed approach provides a new method for the design and fabrication of high performance QLEDs by incorporating multielement semiconductors with variable bandgaps as an ETL.

•CIGS absorber fabricated by c-sputtering of quaternary CuIn0.75Ga0.25Se2 and In targets.•Indium was supplied to eliminate the stoichiometry deviation.•The efficiency of up to 10.29% on 0.35 cm2 area has been achieved.•Such new sputtering route shows great potential for practical applications.In this work, Cu(In1−xGax)Se2 (CIGS) absorber layer is fabricated via radio-frequency sputtering of standard quaternary CuIn0.75Ga0.25Se2 target. In order to achieve the desired Cu-poor absorber film stoichiometry, which is crucial for the device performance, indium is supplied simultaneously with the CIGS deposition by direct current sputtering of indium target for the first time. The influences of sputtering power on composition, structure of the CIGS absorber films and the performances of related solar cells are systematically investigated. The precursor absorber film exhibits uniform and compact surface morphology without peeling and cracking. After selenized in a tube-type rapid thermal processing system under a Se atmosphere, the CIGS absorber layer possesses columnar grains with preferred (112) orientation. Photoelectric measurements of the most efficient device with CdS buffer and ZnO window layer reveals a short-circuit current of 32.02 mA/cm2, an open-circuit voltage of 532 mV, and a fill factor of 60.5 under standard conditions. The efficiency of up to 10.29% on 0.35 cm2 area without antireflection coating has been achieved. Our new sputtering route shows great potential for practical applications of thin film CIGS solar cells with in-line sputtering processes.

The method developed for transferring vertically aligned ZnO nanorod arrays onto arbitrary substrates is highly desirable for the fabrication of ZnO based electronic devices. In this study, vertically aligned ZnO nanorod arrays of different densities were prepared on Al2O3 (0001) substrate by electron beam lithography, combined with the hydrothermal method. The aspect ratio of ZnO nanorod arrays was adjusted by varying the precursor concentration, reaction time, reaction temperature and addition of polyethyleneimine (PEI) molecules in the hydrothermal process. In the following transferring stage, the hot nanoimprint technique was performed, which enabled the ZnO nanorod arrays to easily penetrate into the PMMA transferred layers, while maintaining the integrity and fidelity of the transferred rod arrays. As a result, different density ZnO nanorod arrays were successfully transferred from the donor substrate to ITO glass and more flexible plastic substrates. Furthermore, the surface state of ZnO nanorod arrays was effectively removed through forming Ag electrodes during the transfer process, and Ohmic contacts were successfully formed between the Ag electrodes and ZnO nanorod arrays, which was convenient for the fabrication of high efficiency nanodevices based on ZnO nanorod arrays.

•C60 nanorods were prepared by LLIP method.•The enhanced SPS response in the visible range was obtained for C60 nanorods.•The back-to-back Schottky barriers were formed for a single C60 nanorod on a pair of Au electrodes.One-dimensional (1D) C60 nanorods were synthesized using a liquid-liquid interfacial precipitation method. TEM and SEM were used to characterize the C60 structure. The C60 nanorod growth direction was mainly limited to the [110] direction. Surface photovoltage spectroscopy (SPS) was used to study the optoelectronic property of 1D C60 nanorods film, and greatly enhanced SPS response was observed compared with the pristine C60 film, indicating that the 1D structure of the C60 nanorods is beneficial for the separation and transport of photo-generated charges. The charge transport property of a single C60 nanorod assembled on Au electrodes was also investigated, and it was found that its I-V curve exhibits special rectifying behavior.

•Cu-In-Ga precursors were sputtered from single ternary target.•The selenization of Cu-In-Ga precursors without involving the toxic H2Se.•A highest conversion efficiency of 10.33% was achieved.•A promising strategy for high efficient CIGS solar cells was reported.In this letter, Cu-In-Ga precursor films are fabricated by one-step direct current (DC) sputtering of single ternary alloy target. After the post-selenization by rapid thermal processing (RTP), chalcopyrite-type Cu(In, Ga)Se2 absorber layers in pure phase are obtained. Energy dispersive X-ray spectroscopy (EDS) results reveals that the Cu(In, Ga)Se2 absorber layer is in a Cu-poor stoichiometry. Standard soda lime glass (SLG)/Mo/CIGS/CdS/i-ZnO/ITO/Ag grid structural solar cells are fabricated. A highest conversion efficiency of 10.33% with a Voc of 450 mV, a Jsc of 37.5 mA/cm2 and a FF of 61.3% without antireflection coating has been achieved. Our results demonstrate the selenization of Cu-In-Ga precursors sputtered from a single ternary target is a promising strategy for developing high efficient Cu(In, Ga)Se2 thin film solar cells.

An appropriate diameter and wire-to-wire distance is critical for optimizing the performance of hybrid inorganic/organic photovoltaic devices. For a deep understanding of their influences on such hybrid structures, the well-ordered ZnO nanowires with different diameters are fabricated by the versatile hydrothermal growth. The dependence of the photovoltaic performance on the surface states, wire diameter and wire-to-wire distance is investigated. We demonstrate that the pristine thick ZnO nanowires film possess a higher surface photovoltage (SPV) response than the thin one. This is mainly due to the influence of surface states on the thin ZnO nanowires, which can capture the photo-generated carriers. When the two kinds of ZnO nanowires are fabricated into a hybrid inorganic/organic structure, the thin ZnO nanowires/poly(3-hexylthiophene) hybrid film has a higher SPV response than the thick one, which is contrary to the pristine ZnO nanowires. This is benefited from the smaller diameter and wire-to-wire distance of the thin ZnO nanowires owned. The crystallinity, wire diameter and wire-to-wire distance have the crucial influence on the final photovoltaic performance. The results shown here give us insights toward designing efficient hybrid photovoltaic devices.对基于纳米线结构的无机/有机杂化光伏器件而言,合适的纳米线直径和线间距对其效率有着至关重要的影响。本文采用简单方便的水热生长法合成了具有不同直径和线间距的有序ZnO纳米线阵列,详细研究了表面态对其光伏性能的影响。结果表明,对于未经处理的ZnO纳米线,较大直径的ZnO阵列比较细的样品具有更高的表面光电压响应。这是由于较细的ZnO纳米线表面具有丰富的表面限域态,容易捕获光生载流子,成为载流子复合中心。利用2种不同的氧化锌纳米线构筑了无机/有机杂化薄膜,直径较小的样品比大直径的样品具有更高的表面光电压响应。这是由表面有机材料的钝化所导致,并且小直径的ZnO纳米线具有较小的线直径和线间距,更有利于光生电子-空穴对在有机/无机材料界面的分离。

A composition-tunable ZnxCd1−xSe/ZnO (0 < x ≤ 1) core–shell nanowire array has been fabricated on a conductive glass substrate by the hydrothermal growth and the subsequent ion-exchange reaction. The band gap of the ZnxCd1−xSe shell can be readily tuned by adjusting the temperature of the cation exchange reaction. The charge separation and transport ability of the ZnxCd1−xSe@ZnO with different cation exchange temperatures were investigated. Based on the powerful surface photovoltaic spectrum, the mechanism for the enhanced charge separation was discussed and the charge transport model was established. Moreover, the catalytic activities of three different counter electrode materials such as Cu2S, PbS, and Cu2ZnSnS4 were also evaluated based on the ZnxCd1−xSe@ZnO photoanode. Benefitting from the efficient charge separation at the interface of the ZnxCd1−xSe@ZnO core–shell nanowire array and the novel Cu2S counter electrode with a nanowall structure, a maximum photoelectric conversion efficiency of 1.70% has been achieved. Despite the lower conversion efficiency, our findings provided a better understanding of the charge separation and transport properties in type II core–shell heterojunctions.

•Cu/In/Ga multilayer structure was fabricated by co-sputtering.•Rapid thermal process was employed for the selenization.•CIGS film with better crystallinity was obtained.•Optoelectronic conversion ability of the CIGS film was evaluated by SPV.In this letter, hybrid Cu/In/Ga precursor film was fabricated by co-sputtering of Cu0.8/Ga0.2 and In targets simultaneously. Rapid thermal process was employed for the selenization of Cu/In/Ga precursor film. Homogeneous surface morphology and better crystallinity could be obtained for the CIGS film, which exhibited a preferential orientation with typical chalcopyrite phase. The composition of the CIGS film could be adjusted conveniently by controlling the sputtering power. The strong surface photovoltage response confirmed that the CIGS film had higher optoelectronic conversion ability. Our experimental findings presented in this letter demonstrated that the co-sputtering technique was a promising strategy for developing CIGS absorbers with high performances.

•Cu/Zn/Sn alloy films were prepared by single step electrodeposition.•Suppressed hydrogen evolution reaction.•Homogeneous and compact Cu2ZnSnS4 absorber layer was fabricated.•Photovoltaic activities were evaluated.The Cu/Zn/Sn (CZT) alloy films were prepared by a single step electrodeposition method on fluorine-doped tin oxide (FTO) substrates. In order to suppress the hydrogen evolution reaction, the pH value of the electrolytic solution was adjusted to 7.0 using diethanol amine. The homogeneous and compact Cu2ZnSnS4 (CZTS) absorber materials with better crystallinity were obtained by the subsequent sulfurization. The Raman spectra have not shown any secondary phases when the sulfurization temperature increased to 580 °C. In order to evaluate their photovoltaic activities, the obtained CZTS films were introduced into the QDSSCs as counter electrodes. The highest conversion efficiency of 1.6% with a Voc of 507 mV and a Jsc of 11.2 mA/cm2 were achieved. The high performances of the electrodeposited CZTS CE indicated that they were suitable for application in environmentally-friendly thin film solar cells.

•Collagen Langmuir films were used as templates.•Single crystal calcite has been formed by transformation from amorphous to crystallization.•Structure control of CaCO3 was realized via copying collagen molecules.Collagen Langmuir films were prepared by spreading the solution of collagen over deionized water, CaCl2 solution and Ca(HCO3)2 solution. Resultant collagen Langmuir monolayers were then compressed to a lateral pressure of 10 mN/m and held there for different duration, allowing the crystallization of CaCO3. The effect of crystallization time on the phase composition and microstructure of CaCO3 was investigated. It was found that amorphous calcium carbonate (ACC) was obtained at a crystallization time of 6 h. The amorphous CaCO3 was transformed to rod-like single crystal calcite crystals at an extended crystallization time of 12 h and 24 h, via “copying” the symmetry and dimensionalities of collagen fibers. Resultant calcite crystallites were well oriented along the longitudinal axis of collagen fibers. The ordered surface structure of collagen fibers and electrostatic interactions played key roles in tuning the oriented nucleation and growth of the calcite crystallites. The mineralized collagen possessing both desired mechanical properties of collagen fiber and good biocompatibility of calcium carbonate may be assembled into an ideal biomaterial for bone implants.

The noble metal nanoparticles, such as gold, silver and copper, has been widely incorporated into the photoelectronic devices acting as a light-harvesting antenna and enhancing photocurrents through their light scattering or localized surface plasmon resonance effects. Here, this article presented the investigations into the use of gold nanocrystals to realize the plasmon-enhanced photocurrent generation in TiO2 nanorod-based quantum dots-sensitized solar cells (QDSSCs). By introducing the gold nanocrystals, the short-circuit current density (Jsc) of QDSSCs was enhanced more than 10 % from 7.788 to 8.574 mA/cm2 due to the direct injection of hot electrons from the gold nanocrystals to the photoanode. In order to confirm such conclusion, composite Au/TiO2 nanostructure was also fabricated. Indeed, the hot electrons injection resulted photocurrent density of ~5 mA/cm2 was clearly observed under the visible light irradiation.近年来,金、银、铜等金属纳米颗粒被广泛应用在光电器件中,这些金属颗粒自身特有的光散射效应或等离子共振效应可以用来增强光电器件中的光电流,但较少有研究能够在一维纳米线阵列体系中直接观察到这种光电流产生和增强的现象。本文通过水热反应制备了TiO2纳米棒阵列,通过柠檬酸钠还原HAuCl4·3H2O的方法制备了直径约为20 nm的金纳米晶。为研究金纳米晶在量子点敏化太阳能电池中的光电流增强效应,构筑了ZnS/CdSe/CdS/TiO2核-壳结构的纳米线阵列化光阳极。在该量子点敏化太阳能电池体系中,通过简单的引入金纳米晶,短路电流从7.788 mA/cm2增加到8.574 mA/cm2,增强了约10 %;整个器件的光电转换效率从1.66 %增加到1.73 %,增强了约4.2 %。这种增强效应主要来源于金纳米晶受到激发后电子向ZnS/CdSe/CdS/TiO2光阳极注入所导致。为进一步证实该结论,本文通过原位反应使所制备的金纳米晶与TiO2纳米棒阵列复合,构筑了单一的Au/TiO2复合体系中,在可见光照射下,清楚地观察到了光电流产生现象,而单一的TiO2在可见光照射下,并不能产生光电流。

Periodic individual ZnO nanorod arrays were grown on indium tin oxide (ITO) conductive substrates buffered with a ZnO seed layer. Electron beam lithography was used to pattern the pre-coated poly(methyl methacrylate) (PMMA) layer into a periodic aperture template. Because of the constraint effects of this template, the ZnO nanorod arrays were strictly vertical to the substrate with a controlled pitch. To avoid damage to the electrical properties of conductive substrate, a low temperature (90 °C) hydrothermal route was adopted for the ZnO nanorod synthesis. The nutrient concentration played an important role in obtaining individual ZnO nanorod arrays. Several thin ZnO nanorods could merge into an individual ZnO nanorod at each aperture due to the increased lateral growth rate in ultra-high concentration (0.15 M) nutrient solution. Under the coaction of PMMA aperture template and hydrothermal growth, periodic individual ZnO nanorod arrays on nonsingle crystalline ITO substrates were successfully fabricated. The electrical properties of these periodic ZnO nanorods also were investigated, the current–voltage curve indicated that a barrier-free Ohmic contact formed between ZnO nanorod and ITO interface. The adjustable pitch and high conductance features of the periodic ZnO nanorod arrays made them high performance photoelectric devices.

•Electrodeposition of Cu2O into the ordered ZnO cavity-like nanopatterns.•The interlocked heterojunction design.•A highest PCE of 0.51% with a Jsc of 6.33 mA cm−2.•Such a cell design strategy could also be applied in other type thin film solar cells.The ordered ZnO cavity-like nanopatterns were fabricated through the versatile nanosphere lithography (NSL) technique combined with the hydrothermal growth. Nanostructured Cu2O/ZnO heterojunction solar cell was fabricated by the electrodeposition of Cu2O into the ordered ZnO cavity-like nanopatterns. The formation of intercrossed interface between Cu2O and ZnO could increase the p–n heterojunction area effectively compared to the planar structure. The most efficient cavity-like cell showed a highest PCE of 0.51% with a Voc of 0.24 V, a Jsc of 6.33 mA cm−2, and a FF of 34.5. Significant increase in Jsc and PCE observed in the cavity-like cell was due to the increased p–n heterojunction area and then the enhanced charge carriers collection ability. Our results sheded light on a simple and economic approach to fabricate electrodeposited nanostructural Cu2O/ZnO solar cells with a high efficiency.

Three-dimensional hierarchical ZnO films with lotus-leaf-like micro/nano structures were successfully fabricated via a biomimetic route combining sol–gel technique, soft lithography and hydrothermal treatments. A PDMS mold replicated from a fresh lotus leaf was used to imprint microscale pillar structures directly into a ZnO sol film. Hierarchical ZnO micro/nano structures were subsequently fabricated by a low-temperature hydrothermal growth of secondary ZnO nanorod arrays on the micro-structured ZnO film. The morphology and size of ZnO hierarchical micro/nano structures can be easily controlled by adjusting the hydrothermal reaction time. Wettability of hierarchical ZnO thin films was found to convert from superhydrophilicity to hydrophobicity after a low-surface-energy fluoroalkylsilane modification. Improved wetting properties from hydrophobic to superhydrophobic can be tuned by increasing the growth of ZnO nanorod structures.

Fabricating ZnO nanorod arrays with precisely controlled morphology, alignment, and density is highly desirable but rather challenging. On the other hand, understanding the parameters that affect their final morphology and the growth mechanisms is significant to integrate such patterned ZnO nanorod arrays in various applications. Therefore, ZnO nanorod arrays with different density and morphology were fabricated by electron beam lithography (EBL) combined with the hydrothermal methods in this work. The influences of prepatterned geometry and the growth parameters such as seed layer, the precursor concentration, and the growth time on their final morphology were investigated. Under the coactions of EBL and the subsequent hydrothermal growth, ZnO nanorod arrays with precisely controlled density, position and morphology were achieved. The growth mechanism was also discussed in detail for the ZnO nanorod arrays which confined by the aperture with different size.Keywords: electron beam lithography; growth mechanism; hydrothermal growth; ZnO nanorod arrays;

Flowerlike superstructures of calcium carbonate were synthesized at air–water interface in the presence of pepsin Langmuir monolayers as the biomimetic template. The phase structure, morphology, and microstructure of the products obtained at various crystallization stages were characterized by means of X-ray diffraction, scanning electron microscopy, transmission electron microscopy, selected area electron diffraction and high resolution transmission electron microscopy. The structural and morphological evolution processes of the products from monodispersed nanoparticles to nanoparticle aggregates and flowerlike superstructures were investigated. Results indicate that the flowerlike superstructures of calcium carbonate are assembled from amorphous calcium carbonate nanoparticles. The growth and assembly of calcium carbonate minerals are significantly regulated by the pepsin Langmuir monolayers. Namely, the pepsin Langmuir monolayers stabilize amorphous calcium carbonate nanoparticles and direct their transformation to amorphous aggregates via non-oriented aggregation. The present approach presents a feasible way to manipulate the growth of inorganic crystal, which, hopefully, is to help better reveal the role of proteins in mineralization process and understand the mechanism of biomineralization.Highlights► Pepsin Langmuir monolayer as biomimetic template. ► Flower-like calcite crystals experience a novel assembly and growth process. ► The morphologic evolution and phase transformation were observed. ► The trace of initial nucleation site of CaCO3 at the interface was observed. ► The template directs the crystallization and growth process.

One-dimensional, single-crystalline BiFeO3 nanowires presenting a diameter of 45–200 nm and a length from hundreds of nanometres to several microns have been prepared using an improved hydrothermal method. The characterization results of ZFC and FC magnetizations at different temperatures indicate that single-crystalline BiFeO3 nanowires show a spin-glass transition below the freezing temperature of 55 K.

It is an interesting phenomenon for natural organisms to have control over the shape and size of inorganic nanocrystals and to arrange them into polycrystalline structures. This phenomenon has been driving many attempts to mimic the biomineralization process for synthesizing novel materials. In the present work, novel polycrystalline spindle-like calcite crystals consisting of nanocrystals have been synthesized via a phase transformation process under a Langmuir monolayer of bovine serum albumin (BSA) at room temperature. The polycrystals are composed of hundreds of well assembled calcite nanoneedles consisting of orderly oriented and aggregated nanocrystals transformed from amorphous phase. The evidence for the phase transformation process has been observed in detail by structural characterization of the products at different growth stages. It has been found that the products are evolved from amorphous particles to spindle-like polycrystalline particles. The mineralization process and the interaction between the inorganic and bioorganic components are discussed in relation to relevant protein-mediated nucleation models of biomineralization. Hopefully, the present research is to help understanding the protein-directed formation process of complex structures as well as biomineralization mechanism.Highlights► Albumin Langmuir monolayers as biomimetic template. ► Spindle-like calcite crystals assembled from nanocrystals. ► The crystals experience a morphologic evolution and phase transformation. ► The template directs the crystallization and self-assembly process.

Hydrophobic inorganic films were obtained by direct deposition of copper or silicon onto natural lotus leaves by ion beam sputtering deposition technique. Scanning electron microscopy observations showed a lotus-leaf-like surface structure of the deposited inorganic films. Hydrophobic nature of the inorganic films on lotus leaves had been improved compared to the inorganic films deposited on flat silicon substrates. Water contact angles measured on the lotus-leaf-like copper and silicon films were 136.3 ± 8° and 117.8 ± 4.4°, respectively. The hydrophobic lotus-leaf-like inorganic films had been repeated used as nanoimprint stamps. Negative structures of lotus-leaf-like inorganic films were obtained on the polystyrene resist layers.

Surface-patterned ZnO thin films were fabricated by direct imprinting on ZnO sol and subsequent annealing process. The polymer-based ZnO sols were deposited on various substrates for the nanoimprint lithography and converted to surface-patterned ZnO gel films during the thermal curing nanoimprint process. Finally, crystalline ZnO films were obtained by subsequent annealing of the patterned ZnO gel films. The optical characterization indicates that the surface patterning of ZnO thin films can lead to an enhanced transmittance. Large-scale ZnO thin films with different patterns can be fabricated by various easy-made ordered templates using this combination of sol–gel and nanoimprint lithography techniques.

The ZnO nanowires (NWs) array/poly(3-hexylthiophene) (P3HT) hybrid prototype device was fabricated. An ultraviolet (UV) light of λ = 350 nm is used to investigate the photo-electric properties of the ZnO NWs array and hybrid structure. In this way, we can avoid the excitation of P3HT, which can give us a real electron transport ability of ZnO NWs itself. Our results demonstrated a higher and faster photo-electric response of 3 s for the hybrid structure while 9 s for the ZnO NWs array. The surface states related slow photo-electric response was also observed for them. The charge transfer mechanism and the influence of surface states were discussed. The current work provides us profound understandings on the electron transport ability of ZnO NWs array in a working hybrid polymer solar cell, which is crucial for optimizing the device performance.

Au nanoplates were generated by spontaneous reduction of chloroaurate ions (AuCl4−) under bovine serum albumin (BSA) Langmuir monolayers at room temperature. The structure of the resulting Au particulates was analyzed by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), selected-area electron diffraction (SAED), and high resolution transmission electron microscopy (HRTEM). The results showed that BSA provided dual functions for both reducing Au3+ ions and directing anisotropic growth of Au particles into plate-like structure as well. Amorphous Au particulates were obtained firstly in a relatively short reaction time, and then anisotropic Au nanoparticles were generated at extended reaction durations. The triangular Au nanoplates oriented along (1 1 1) basal planes were obtained via the reduction of chloroaurate ions by BSA with a relatively longer reaction duration. The present research provides a biological route to produce single-crystalline gold nanoplates with a wide variety of applications, and it also verifies that the interaction between protein/peptide and gold ions/surface may be used advantageously for green chemical synthesis of nanogold. Hopefully, this would contribute to promote genuine green biomimetic synthesis of nanomaterials with prescribed geometrical features where rationally designed multifunctional peptides are preferred.

Langmuir–Blodgett monolayers of behenic acid (BA) were prepared by the vertical deposition method and their morphological evolutions and nano-mechanical anisotropy were studied by atomic force microscopy (AFM) and lateral force microscopy. Results show that there are platforms in the differential surface pressure-area (π-A) isotherm presenting linear relations between the chain tilting angles and surface pressures. The reorganization, appearance and disappearance of defects such as pinholes and holes can strongly affect the profile of π-A isotherm; AFM images reflect evolution rules from pinholes to holes, and from monolayer to bilayers along with compression and relaxation of structures in BA monolayer. Due to higher molecule density and larger real contact area, the tip-monolayer contacts at 15 and 25 mN/m correspond to the Derjaguin–Muller–Toporov (DMT) model showing long-ranged interaction forces. But owing to more easily-deformed conformations, contacts at 5 and 35 mN/m accord with the Johnson–Kendall–Robert and DMT transition cases exhibiting short-ranged interface interactions. A little higher friction is proved in the direction perpendicular to the deposition.

Self-organized dithieno [3,2-b:2’,3’-d] thiophene-2,5-dicarboxylic acid (A) and dithieno [2,3-b:3’,2’-d] thiophene-2,5-dicarboxylic acid (B) films were prepared through solvent-induced order-disorder transition method. The arrangement of the two molecules on substrates were observed by atomic force microscopy (AFM), which demonstrated that A was arranged orderly in a certain angle on mica, while B was flat-flying on mica. The optical and conductance properties in micro region of these two compound films were characterized by UV-vis absorption spectroscopy, fluorescence spectroscopy and conductive atomic force microscopy (C-AFM). The results revealed that the fluorescence and absorption peaks of A had a large red shift in comparison with those of B. The conductance of the J-aggregates for A is three orders magnitude higher than that of B. It is concluded that the large conductance difference mainly comes from different aggregation structures and orientations of these two molecules on substrate.

Highly crystalline TiO2 nanostructures were prepared through a facile inorganic acid-assisted hydrothermal treatment of hexagonal-structured assemblies of nanocrystalline titiania templated by cetyltrimethylammonium bromide (Hex-ncTiO2/CTAB Nanoskeleton) as starting materials. All samples were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The influence of hydrochloric acid concentration on the morphology, crystalline and the formation of the nanostructures were investigated. We found that the morphology and crystalline phase strongly depended on the hydrochloric acid concentrations. More importantly, crystalline phase was closely related to the morphology of TiO2 nanostructure. Nanoparticles were polycrystalline anatase phase, and aligned nanorods were single crystalline rutile phase. Possible formation mechanisms of TiO2 nanostructures with various crystalline phases and morphologies were proposed.

Compact large area Zn5(OH)8(NO3)2·2H2O, Co5(OH)8(NO3)2·2H2O and Co-doped Zn5(OH)8(NO3)2·2H2O thin films with uniform surface morphology and good orientation were synthesized by an unusual dual-template biomimetic approach. In such a biomimetic system, a bovine serum albumin Langmuir monolayer was used as one organic matrix template, whereas the vapor–liquid interface generated by the vapor diffusion of catalyst (ammonia) served as the other nucleation template providing kinetic control. The crystallinity, morphology and overall chemical composition of thin films were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The formation process of the Zn5(OH)8(NO3)2·2H2O films was discussed in detail. Compared with the method with only organic template, the synergetic effect of the dual template plays an important role in the formation of thin films. The method developed here provides a novel route for growing large area and well-oriented thin films at room temperature.

Ordered Ag nanowire arrays with high aspect ratio and high density self-supporting Ag nanowire patterns were successfully prepared using potentiostatic electrodeposition within the confined nanochannels of a commercial porous anodic aluminium oxide (AAO) template. X-ray diffraction and selected area electron diffraction analysis show that the as-synthesized samples have preferred (220) orientation. Transmission electron microscopy and scanning electron microscopy investigation reveal that large-area and ordered Ag nanowire arrays with smooth surface and uniform diameter were synthesized. Surface-enhanced Raman Scattering (SERS) spectra show that the Ag nanowire arrays as substrates have high SERS activity.

Calcium carbonate nanoparticles were generated beneath the Langmuir monolayer of bovine serum albumin (BSA) via templated mineralization. The BSA monolayer and calcium carbonate nanoparticles were characterized based on the measurement of surface pressure–area (π–A) isotherms and area–time curve, and analyses of transmission electron microscopy (TEM), selected area electron diffraction (SAED), scanning electron microscopy (SEM), and X-ray diffraction (XRD) as well. The interaction mechanisms between BSA and calcium carbonate and the role of amorphous calcium carbonate (abridged as ACC) and lattice match in controlling the morphologies and microstructures of the target Calcium carbonate (CaCO3) crystals were discussed, and a model was suggested to illustrate the formation of CaCO3 crystals in the presence of the BSA monolayer. Results indicated that the calcium carbonate nanoparticles were formed through a multi-step process in the presence of the BSA monolayer. Both the amorphous calcium carbonate and lattice match played important roles in terms of the controlled biomineralization and organic matrix-mediated synthesis of CaCO3 nanoparticles. The transformation of amorphous calcium carbonate phase to calcite crystal phase could provide direct evidences to the multistep crystallization process in biomineralization. And the present approach could be used to guide the synthesis of advanced inorganic nanomaterials via simulated biomineralization under mild conditions.

High-density ZnO nanorods with quadrangular and hexagonal cross sections were synthesized by chemical vapor deposition combining with a sol–gel method. It was found that the different morphologies could be obtained by changing the growth temperature. The growth mechanism was presented. The photoluminescence (PL) spectra demonstrated that both the quadrangular and hexagonal cross sections ZnO nanorods had a weak ultraviolet (UV) emission but a very strong and wide green emission. Interestingly, the quadrangular ZnO nanorods showed a stronger green emission than the hexagonal ones. Our X-ray photoelectron spectroscopy (XPS) results indicated that the quadrangular ZnO nanorods had a higher oxygen adsorption ability, and which should be the primary reason for its stronger green emission.

Multiferroic BiFeO3 (BFO) nanotube arrays (∼100 nm in diameter and ∼50 µm in length) were synthesized by the sol-gel method utilizing the anodic aluminum oxide (AAO) membrane technique. The microstructure and chemical components of the BFO nanotubes were investigated using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectrometer (XPS). The BFO nanotubes exhibited polycrystalline microstructures. The novel Y-junction BFO nanotubes were simultaneously fabricated.

Monodisperse Fe3O4 and FeO nanocrystals (NCs) with different sizes (from 10 nm to 50 nm) and different shapes (cube, sphere, and ellipsoid) were synthesized by simply adjusting reaction temperature or molar ratio of Fe/oleic acid (OA) during the decomposition of FeO(OH) in noncoordinating solvent. The concentration of OA affected the nucleation and growth of NCs by improving the chemical reaction driving force during the syntheses of different types of iron oxide NCs. It has been found that the reaction temperature influenced the reaction activity between FeO(OH) and OA. The structure of Fe oleate complexes was studied using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Raman spectroscopy, and transmission electron microscopy (TEM) were used for structural and chemical characterization of as-prepared iron oxide NCs.Possible reaction routes for FeO(OH) with OA to synthesize monodisperse iron oxide nanocrystals.

Large quantities of CdS nanorods are successfully synthesized through Cd(CH3COO)2·2H2O reacting with Na2S·9H2O and EDA in aqueous solution. XRD result shows that the sample is of hexagonal structure. And TEM result shows that the morphologies of the resulting CdS are mainly in three-armed rod-like structure with a diameter of 10–15 nm and a length of 100 nm. The nanocomposites of CdS/PVK with different molar ratios are prepared by spin coating method on tin-doped indium oxide (ITO) substrate. A notable decrease of photoluminescence (PL) efficiency and a significant enhancement of surface photovoltage signal have been observed in CdS/PVK composites when the molar fraction of CdS increases. We interpret these results as the energy level matching between CdS and PVK in nanocomposites. This energy level matching facilitates fast interfacial charge transfer then increases the separation efficiency of electron-hole pairs and the carrier generation efficiency. The detailed charge transfer process has also been demonstrated.

Sodium titanate nanotubes have been prepared and modified chemically with CdSe quantum dots (QDs) using bifunctional modifiers (HS-COOH). Their photovoltaic characteristics have also been studied. The results indicate that the surface photovoltage response of nanotubes extends to the visible light region, and the intensity of surface photovoltage is enhanced after modification with CdSe QDs. The field-induced surface photovoltage spectroscopy (FISPS) shows that sodium titanate nanotubes have different photovoltaic response before and after modification. That is, the surface photovoltaic response of pure sodium titanate nanotubes increases with the enhancement of positive applied bias and decreases with the enhancement of negative applied bias. Meanwhile, the surface photovoltaic response of CdSe modified sodium titanate nanotubes is different from that of the pure sodium titanate nanotubes. The whole spectrum increases with the enhancement of applied bias at the first stage. However, when the applied bias reaches a certain value, the surface photovoltage response keeps increasing in some spectrum regions, while decreasing in other spectrum regions. This novel phenomenon is explained by using an electric field induced dipole model.

We report a new method to synthesize monodisperse zinc blende HgTe nanocrystals at room temperature in noncoordinating solvent—octadecene. Thiol was needed to control the reaction at a suitable nucleation and growth speed. In the early stage of the reaction, HgTe nanocrystals formed aggregates, and then the aggregates were dispersed and individual dot-shaped nanocrystals were formed with stronger photoluminescence emitting. UV–vis, photoluminescence, and TEM have been used to study the properties of as-prepared HgTe nanocrystals.

Langmuir–Blodgett (LB) films of azobenzene dye of 2-hydroxyl-3-(4-methoxyl)-naphthanilide-azodiphenyl (AS-RL) and its hybrid films with behenic acid (BA) and octadecylamine (ODA) were investigated by tapping mode atomic force microscopy and ultraviolet visible light absorption spectroscopy. Wavy line-shaped or fingerprint-like dye aggregates were observed in the pure dye LB films. BA and ODA were used to modulate and control the structure of the dye aggregates and different patterns resulted in changing the molar ratio of dye molecules in the composites films, such as long lines (AS-RL/BA = 1:2), sheets (AS-RL/ODA = 1:2), wide lines (AS-RL/ODA = 1:1), and ordered lines (AS-RL/ODA = 2:1).

Fractal-like nanopatterned DNA thin films have been fabricated on mica substrate by Langmuir–Blodgett (LB) technique. Structures and components of DNA nanopatterns were investigated using atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The effect of surface pressure on the transferred DNA composite films has been studied. Scanning force microscopic observations revealed that the surface structure and morphology of DNA nanopatterns can be well controlled by changing the surface pressure. The growth mechanism of the fractal-like nanopatterns is discussed in terms of the diffusion-limited aggregation (DLA) model. The formation of large-scale DNA networks provided a well-defined template for the construction of nanocomposite films. Patterns of silver metal were prepared on DNA networks by subsequent metallization process.

Spectra of octadecylamine (ODA) Langmuir monolayers and egg phosphatidylcholine (PC)/ODA-mixed monolayers at the air–water interface have been acquired. The organization of the monolayers has been characterized by surface pressure–area isotherms. Application of polarized optical microscopy provides further insight in the domain structures and interactions of the film components. Surface-enhanced Raman scattering (SERS) data indicate that enhancement in Raman spectra can be obtained by strong interaction between headgroups of the surfactants and silver particles in subphase. By mixing ODA with phospholipid molecules and spreading the mixture at the air–water interface, we acquired vibrational information of phospholipid molecules with surfactant-aided SERS effect.

An appropriate diameter and wire-to-wire distance is critical for optimizing the performance of hybrid inorganic/organic photovoltaic devices. For a deep understanding of their influences on such hybrid structures, the well-ordered ZnO nanowires with different diameters are fabricated by the versatile hydrothermal growth. The dependence of the photovoltaic performance on the surface states, wire diameter and wire-to-wire distance is investigated. We demonstrate that the pristine thick ZnO nanowires film possess a higher surface photovoltage (SPV) response than the thin one. This is mainly due to the influence of surface states on the thin ZnO nanowires, which can capture the photo-generated carriers. When the two kinds of ZnO nanowires are fabricated into a hybrid inorganic/organic structure, the thin ZnO nanowires/poly(3-hexylthiophene) hybrid film has a higher SPV response than the thick one, which is contrary to the pristine ZnO nanowires. This is benefited from the smaller diameter and wire-to-wire distance of the thin ZnO nanowires owned. The crystallinity, wire diameter and wire-to-wire distance have the crucial influence on the final photovoltaic performance. The results shown here give us insights toward designing efficient hybrid photovoltaic devices.

•ZO films have been deposited by radio frequency (RF) magnetron sputtering.•The minimum resistivity is as low as 6.1 × 10−4 Ω cm.•The surface microstructure of AZO is beneficial to scatter the incident light.•Conversion efficiency of 7.8% is achieved based on the AZO transparent electrode.Aluminum-doped zinc oxide (AZO) has attained intensive attention as being a very good transparent conducting oxide for photovoltaic applications. In this work, AZO films have been deposited on glass substrate by radio frequency (RF) magnetron sputtering. The influences of substrate temperatures on morphological, structural, optical and electrical properties of AZO films were systematically investigated. The results indicate that all AZO films have the hexagonal structure with c-axis preferred orientation. Morphological and electrical measurements have revealed that the substrate temperatures have strong influence on the microstructure, optical and electrical properties of AZO films. The AZO film is highly transparent from ultraviolet up to near infrared range with highest average transparency exceeding 83%. The minimum resistivity is as low as 6.1 × 10−4 Ω cm. The carrier concentration and mobility are as high as 3.357 × 1020 cm−3 and 30.48 cm2/Vs, respectively. Finally, the performances of the AZO film are evaluated by its practical application in Cu(In1-xGax)Se2 (CIGS) photovoltaic device as a transparent electrode. Benefited from its highly transparent and conductive feature, the most efficient device reveals an efficiency of 7.8% with a short-circuit current density of 28.99 mA/cm2, an open-circuit voltage of 430 mV, and a fill factor of 62.44 under standard conditions.

Since the introduction of inorganic ZnO nanoparticles as an electron transport layer (ETL) material, the device performance of colloidal quantum dot light-emitting diodes (QLEDs) has been rapidly improved. Although there have been rapid advances in luminance, efficiency and lifetime, device performance is still limited by balanced electron/hole injection into the quantum dot layer. In this study, solution-processed Zn1−xMgxO (ZMO) films with tunable bandgaps were designed as an ETL for high performance QLEDs. It was found that the band gap of ZMO broadened as the energy level varied with increasing Mg concentration. As a consequence, the energy barrier between the Al cathode and ZMO ETL was tuned to balance the electron/hole injection towards a better device performance. The luminance intensity increased from 20229 to 36685 cd m−2, while the current efficiencies increased from 3.74 to 13.73 cd A−1, and the power efficiencies increased from 4.65 to 12.94 lm W−1 with a 0.05% Mg doping ratio. Particularly, the optimized device based on ZMO exhibited an enhanced external quantum efficiency (EQE) of 9.46%, which was 3.67-fold compared with that of pure ZnO nanoparticles (2.58%). The proposed approach provides a new method for the design and fabrication of high performance QLEDs by incorporating multielement semiconductors with variable bandgaps as an ETL.

Compact large area Zn5(OH)8(NO3)2·2H2O, Co5(OH)8(NO3)2·2H2O and Co-doped Zn5(OH)8(NO3)2·2H2O thin films with uniform surface morphology and good orientation were synthesized by an unusual dual-template biomimetic approach. In such a biomimetic system, a bovine serum albumin Langmuir monolayer was used as one organic matrix template, whereas the vapor–liquid interface generated by the vapor diffusion of catalyst (ammonia) served as the other nucleation template providing kinetic control. The crystallinity, morphology and overall chemical composition of thin films were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The formation process of the Zn5(OH)8(NO3)2·2H2O films was discussed in detail. Compared with the method with only organic template, the synergetic effect of the dual template plays an important role in the formation of thin films. The method developed here provides a novel route for growing large area and well-oriented thin films at room temperature.

One-dimensional, single-crystalline BiFeO3 nanowires presenting a diameter of 45–200 nm and a length from hundreds of nanometres to several microns have been prepared using an improved hydrothermal method. The characterization results of ZFC and FC magnetizations at different temperatures indicate that single-crystalline BiFeO3 nanowires show a spin-glass transition below the freezing temperature of 55 K.