A dopant-free hole-transporting material (HTM), with (2-ethylhexyl)-9H-carbazole as core and N,N-di-p-methylthiophenylamine as end groups, termed CMT, has been designed and synthesized by a simple method. For the first time, four methylthiol groups have been introduced, rather than methoxy groups, at the para position of the diphenylamine. Under AM 1.5 illumination at 100 mW cm–2, perovskite solar cells based on CH3NH3PbI3 with pristine CMT as the HTM achieved a power conversion efficiency of 13.05%, with a short-circuit current density of 21.82 mA cm–2, an open-circuit voltage (VOC) of 1.03 V, and a fill factor of 58.23%. The value of VOC is comparable to that of the device based on 2,2′,7,7′-tetrakis(N,N-di-para-methoxy-phenylamino)-9,9′-spirobifluorene, which was 1.02 V.

A hole-transporting material (HTM) based on (2-ethylhexyl)-9H-carbazole as the core and N,N-di-p-methoxyphenylamine as the end group (CMO) has been designed. CMO with a simple structure can be synthesized by a one-step process in a high yield and it shows good solubility in solvents. Steady-state and time-resolved photoluminescence measurements show that CMO has significant charge extraction ability. Planar perovskite solar cells (pero-SCs) based on CMO as the HTM showed a high power conversion efficiency of 15.92%. For reference purposes, pero-SCs based on 2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenylamine)-9-9′-spirobifluorene (Spiro-OMeTAD) were fabricated and a PCE of 16.70% was reached. CMO is one of the simplest HTM materials reported, which shows a PCE comparable to that of Spiro-OMeTAD at the same time.

Tandem solar cells combining a wide bandgap, efficient perovskite absorber with a low bandgap photovoltaic module, such as a c-Si cell, can potentially achieve a high theoretical efficiency of over 30%. Instead of using the conventional parallel stacking tandem, we report here a reflective tandem configuration, with the perovskite solar cell acting as the spectral filter that absorbs high energy photons, while sub-bandgap photons are reflected to a Si sub-cell using a highly reflective back metal electrode. The perovskite solar cell exhibits a high reflectance of over 60% in the near infrared spectral region, which allows the subsequent silicon cell to absorb photons in this region, resulting in a high current density of 13.03 mA cm−2. In such a tandem configuration, we achieved a combined efficiency of 23.1% using a four-terminal measurement. This result demonstrates the promise of employing perovskite solar cells in a reflective tandem for a high efficiency solar energy conversion system, with an efficiency of up to 30%.

•Use of mist flow jet impingement cooling technology on ultra-thin glass.•Correlation for surface average Nusselt number is given.•Controlling droplet diameter can obtain better heat transfer uniformity.•Mist flow jet impingement reduces the amount of air and save energy.The thinning and miniaturization of components, such as liquid crystal display and solar cells, has increased the market demand for tempered ultra-thin glass. The physical tempering in glass, which is less than 2 mm thick, is difficult to achieve in air jet impingement. In this study, we propose the use of mist flow jet impingement cooling technology on ultra-thin glass. The effects of the mist flow droplets diameters, nozzle inlet temperature, and mass fraction on the heat transfer rate and uniformity are numerically studied. Our performance in terms of the heat transfer rate and the uniformity is accounted for through an evaluation of the surface-averaged temperature, averaged Nusselt number, surface-averaged Nusselt number, and surface standard deviation percentage of the Nusselt number. The empirical correlation for the surface averaged Nusselt number as a function of mist flow droplet diameters is provided. The droplet diameter is the major factor affecting the heat transfer rate, while the jet inlet temperature is a minor factor. We can obtain a better heat transfer uniformity by controlling the droplet diameter of the mist flow jet impingement. Using mist flow jet impingement, we would not only greatly reduce the amount of air and save energy, but also meet the needs of sudden cooling for tempered glass with a thickness of less than 2 mm.

•SnS films with different Sn contents were fabricated by thermal co-evaporation.•An excess of Sn can result in a change of the SnS semiconducting film from p-type to n-type.•A high mobilities of 7.29 cm2/V ∙ s in p-type SnS was obtained.SnS films with different Sn contents were fabricated by thermal co-evaporation. The variation in structures, optical and electrical properties of SnS with different Sn contents was systematically investigated. The prepared films were characterized by X-ray diffraction, field emission scanning electron microscopy, and energy dispersive spectroscopy analysis. An excess of Sn can result in a change of the SnS semiconducting film from p-type to n-type. The SnS films showed band gaps in the range of 1.25–1.57 eV and high mobilities of 7.29 cm2/V ∙ s, indicating suitability for application in photovoltaic cells. The photoelectric conversion efficiency (PCE) of the heterojunction solar cell was 1.26% with a open circuit voltage (VOC) of 0.153 V and a short circuit current density (JSC) of 29.61 mA/cm2.

•Organic molecules have been synthesized applied for organic solar cells.•The molecules show different photovoltaic properties due to tiny change.•The cells based on new molecule reached a power conversion efficiency of 3.45%.Organic molecule materials (BDT-HTH-BT and BDT-BT-HTH) applied for solution-processable organic solar cells (OSCs) have been synthesized to investigate the impact of the location of acceptor unit on the photovoltaic properties. Benzothiadiazole (BT) group was introduced as an acceptor unit, which was linked to bithienyl-substituted benzodithiophene (BDT) unit directly in BDT-BT-HTH or with hexyl-thiophene unit in BDT-HTH-BT, respectively. The molecular weight of BDT-BT-HTH and BDT-HTH-BT are the same. However, due to the different position of the BT unit, BDT-HTH-BT and BDT-BT-HTH exhibit apparently different optical and electrochemistry properties, corresponding to the photovoltaic properties. The OSCs device based on a blend of BDT-BT-HTH and PC71BM (1:0.8, w/w, 0.5% DIO) reached a PCE (power conversion efficiency) of 3.45%, with a short-circuit current density of 6.85 mA cm−2, an open-circuit voltage of 0.815 V and an fill factor of 61.8%. In comparison, the PCE of the OSCs device based on BDT-HTH-BT as donor material is recorded only 0.32% under the same experimental conditions.

•Synthesis of Au nanograin decorated aligned multiwall carbon nanotube (CNT) sheets.•Au nanograins results in fast radial ion diffusion and enhance axial electron transport.•The flexible linear solid supercapacitor exhibits an ultrahigh rate performance.•A remarkable capacitance retention of about 95% over 1000 stretch/release cycles.Linear supercapacitors suffer a severe loss of capacity at high rates due to the trade-off of radial ion diffusion and axial electron transport. Optimizing axial conductivity of electrodes is a key to circumvent this trade-off. We report here the synthesis of Au nanograin decorated aligned multiwall carbon nanotube (CNT) sheets, followed by the incorporation of polyaniline (PANI). The embedded Au nanograins results in fast radial ion diffusion and enhance axial electron transport in the linear electrodes. The flexible linear solid supercapacitor fabricated by twisting two PANI@Au@CNT yarns exhibits an outstanding electrochemical performance with a total volumetric capacitance of ∼6 F cm−3 at scan rate up to 10 V s−1. Diameter of the electrode has little effect on volumetric capacitance even at high scan rates because of its high electrical conductivity. Highly stretchable supercapacitors with high rate performance and excellent cycling and stretching stability have been also fabricated using buckled linear electrodes made by wrapping PANI@Au@CNT sheet on elastic rubber fibers. The stretchable linear supercapacitor possesses a stable total volumetric capacitance of up to ∼0.2 F cm−3 at scan rate of 1 V s−1 and at 400% strain, and remarkable capacitance retention of about 95% over 1000 stretch/release cycles.

•A new laminated structure is proposed to boost the rate of linear supercapacitors.•AgNWs/CNT sheet improves the axial electron transport greatly.•Serially connected linear supercapacitors illuminate an electronic watch successfully.In this study, a new laminate CNT sheet/AgNWs/CNT sheet structure is proposed to improve the rate performance of solid-state long linear supercapacitors. The fabricated 16 cm long linear supercapacitor with a ∼40 μm diameter electrode has a specific length capacitance of 6.26 mF cm−1 at 20 mV s−1. Further, it exhibits good capacitance behavior even at scan rate of 100 mV s−1. AgNWs/CNT sheet improves the axial electron transport greatly and consequently boosts the rate performance of linear supercapacitor. Serially connected linear supercapacitors were found to possess good electrochemical performance, and the device was able to illuminate an electronic watch successfully. This study provides an effective method to enhance the rate performance of long linear supercapacitors, which has potential applications in wearable and portable electronics and micro robots.

•AZTS homojunction was obtained by a one-time sulfurization on a laminated precursor.•AZTS homojunction was incorporated in cells and an efficiency of 0.87% was achieved.•This is the first report on the fabricated quaternary semiconductor homojunction solar cells.In this work, an Ag2ZnSnS4 (AZTS) homojunction film was obtained by the one-time introduction of sulfur on a laminated structure precursor film. Furthermore, this homojunction film was incorporated in the solar cell with a structure of Mo/AZTS /i-ZnO/ITO and an efficiency of 0.87% was achieved. This is the first report on the fabricated quaternary semiconductor homojunction solar cells. This work provides a new idea and method for the fabrication of thin film solar cells.

One of the main issues for high-performance perovskite solar cells (PSCs) is the fabrication of high-quality perovskite films. However, a thermal annealing process is generally required for a high crystallinity film via a typical solution-based method, which may result in inhomogeneous nucleation, and is time-consuming. Herein, we investigate the effects of different solvents on the morphology and the crystallinity of perovskite films systematically and further develop a solvent-technique for uniform perovskite films without the need for annealing. N-Methyl-2-pyrrolidone (NMP) has been adopted as a high-boiling-point solvent and a complexant, combined with the commonly used N,N-dimethylformamide (DMF) or dimethylacetamide (DMAc), to improve the quality of perovskite films and enhance the corresponding device performance. PSCs fabricated from DMAc/NMP co-solvents using the post-annealing process show the best power conversion efficiency (PCE) of 17.38%, which is about 10% improvement compared to that of the device based on DMF/dimethyl sulfoxide (DMSO) or DMAc/DMSO co-solvents. Notably, 17.09% efficiency has been achieved even without any post-annealing process for the device based on DMAc/NMP co-solvents. However, only 3.81% efficiency can be obtained for the device based on DMAc/DMSO co-solvents under the same conditions. The observed phenomenon is mainly due to the fact that the NMP-included solvents can induce an instant crystallization once the anti-solvent drips on the films at room temperature (RT). Our study may provide a new approach to prepare high-quality perovskite films at RT, which would simplify the fabrication procedures and reduce the cost of efficient PSC manufacture.

Balancing the high power conversion efficiency (PCE) and long-term stability of organic–inorganic hybrid perovskite solar cells (Pero-SCs) is a challenging factor for the commercialization of solar cells. Herein, a cost-effective and widely available water-soluble additive, polyvinyl alcohol (PVA), has been adopted to improve the film quality of CH3NH3PbI3 and enhance the efficiency and long-term tolerance to humidity. A PCE of 17.4% has been achieved for the device with PVA, showing an 11.6% increase compared to those of the devices without the additive. Most importantly, the unencapsulated devices retain over 90% of their initial efficiency even after 30 days in a high humidity environment (90% relative humidity), exhibiting greater humidity tolerance and superior stability. Our studies present a simple solution-based approach to fabricate high efficiency solar cells with long-term stability under high humidity conditions, potentially revealing new methods for the mass production of Pero-SCs.

Organic–inorganic halide perovskites have emerged as attractive materials for use in photovoltaic cells. Owing to the existence of dangling bonds at the grain boundaries between perovskite crystals, minimizing the charge recombination at the surface or grain boundaries by passivating these trap states has been identified to be one of the most important strategies for further optimization of device performance. Previous reports have mainly focused on surface passivation by inserting special materials such as graphene or fullerene between the electron transfer layer and the perovskite film. Here, we report an enhanced efficiency of mesoscopic perovskite solar cells by using graphene quantum dots (GQDs) to passivate the grain boundaries of CH3NH3PbI3. The highest efficiency (17.62%) is achieved via decoration with 7% GQDs, which is an 8.2% enhancement with respect to a pure perovskite based device. Various analyses including electrochemical impedance spectroscopy, time-resolved photoluminescence decay and open-circuit voltage decay measurements are employed in investigating the mechanism behind the improvement in device performance. The findings reveal two important roles played by GQDs in promoting the performance of perovskite solar cells – that GQDs are conducive to facilitating electron extraction and can effectively passivate the electron traps at the perovskite grain boundaries.

Metal halide perovskites are newcomer optoelectronic materials that have attracted enormous attention and single crystal offers better stability and optical electronic performance. In this background, a lead-free, air-stable, effective material of bismuth halide perovskite is highly sought-after. Herein, millimeter-scale single-crystal A3Bi2I9 (A = Cs+ or methylammonium (MA+)) perovskites were synthesized via a facile hydrothermal approach and characterized by various means. Raman spectroscopy results in a layered cleavage distribution. Spin-coating of these compounds produced thin films with uniform surface morphologies, high carrier mobility and superior stabilities. Trivalent-bismuth-based materials were used as the photoactive layer in solution-processed heterojunction solar cell devices, which is a conceptual beneficial exploration and yield power conversion efficiencies of ~ 0.2%.

Inorganic metal chalcogenide compounds based thin-film solar cells are regarded as most promising candidates for film power modules due to their high efficiencies with low cost. From top to bottom, the semiconductor thin film solar cell is made up of a metal layer, an absorber material, a buffer layer, and a transparent conducting oxide (TCO). Indium tin oxide (ITO) is a common material for transparent conducting films used as a front contact layer on solar cells. Although extensive studies have been performed on the deposition and properties of ITO films, few studies focused on the effect of the sputtering deposition conditions of ITO on the buffer layer. In this study, ITO thin films were deposited on soda-lime glass (SLG) by conventional RF-magnetron sputtering. The dependence of the electrical and crystalline properties on different substrate temperature, different RF power and different introducing rate of oxygen was investigated. The deposition conditions of ITO not only have influences on the structure and properties of ITO but also affect the buffer layer underneath. Therefore, we investigated the effect of ITO deposition parameters on the crystallization and electrical and optical properties of sputtered CdS films and, in turn, on the resulting device characteristics.

•Transient heat transfer characteristics of small-jet impingement is studied.•Heat transfer near stagnation and boundary point is opposite with the decrease of H/D.•Position of vortex moves from boundary to stagnation point with the decrease of H/D.Numerical studies on the transient heat transfer characteristics of small-air-jet impingement under the condition of a large temperature difference between the nozzle and the plate are presented. The Reynolds number (Re) varied from 20,000 to 60,000 which is based on the hydraulic diameter of the circular jet. The nondimensional jet-to-plate distance (H/D) with nozzle diameter (D) of 5 mm is varied from 0.2 to 2. Variations in the stagnation point and boundary point Nusselt numbers with cooling times are discussed. It was found that with the decrease of jet-to-plate distance the heat transfer near stagnation point is enhanced, while it is decreased near boundary point. The velocity field is proposed as an explanation for the observed transient heat transfer.

•Two recyclable nitrite sensing composite samples were constructed through a core-shell structure.•Fe3O4 core, silica molecular sieve and two rhodamine probes were used as core, shell and chemosensors, respectively.•Nitrite sensing behavior was discussed based on emission intensity quenching.•A static sensing mechanism and LOD of 1.2 μM were reported.Two recyclable nitrite sensing composite samples were designed and constructed through a core-shell structure, with Fe3O4 nanoparticles as core, silica molecular sieve MCM-41 as shell and two rhodamine derivatives as chemosensors, respectively. These samples and their structure were identified with their electron microscopy images, N2 adsorption/desorption isotherms, magnetic response, IR spectra and thermogravimetric analysis. Their nitrite sensing behavior was discussed based on emission intensity quenching, their limit of detection was found as low as 1.2 μM. Further analysis suggested a static sensing mechanism between nitrite and chemosensors through an additive reaction between NO+ and chemosensors. After finishing their nitrite sensing, these composite samples and their emission could be recycled and recovered by sulphamic acid.Download high-res image (219KB)Download full-size image

•Highest efficiency of 5-in. n-type PERT cell was 21.98% using industrially technology.•An average of 21.85% cell efficiency was achieved.•Power loss analysis on Voc, Isc and FF are presented.A high-efficiency front junction n-type passivated emitter and a rear total diffusion (n-type PERT) solar cell with the front boron diffusion passivated by a Al2O3/SiNx stack layer deposited by plasma enhanced chemical vapor method and the rear with phosphorus total diffusion and Al evaporated local contact are presented in this paper. The main purpose of this study was to develop industrially feasible front junction n-type PERT solar cells with high-efficiency; these were realized on a large area of n-type industrial 5- and 6-in. wafers. An average of 21.85% cell efficiency was achieved on 5-in. wafers, and the highest cell convert efficiency of 21.98% was achieved with Voc of 683.8 mV, Jsc of 40.13 mA/cm2, and FF of 80.11%. For 6-in. cells, we get Fraunhofer independently confirmed efficiency of 21.49% with a Voc of 674.1 mV, a Jsc of 39.77 mA/cm2, a FF of 80.18%. Details of cell fabrication and results are presented, followed by a best cell power loss analysis on Voc, Isc and FF.

•CCTS film was successfully prepared by co-sputtering technique and sulfurization.•The high carrier mobility 21.4 cm2 v−1 s−1 was successfully obtained.•The efficiency of the CCTS for the solar cell was 1.14%.Cu2CdSnS4 is an important candidate material for thin-film solar cell absorber layers. In this work, a low-cost Cu2CdSnS4 thin film with a cernyite structure has been successfully fabricated by sulfurization of the precursor film obtained by co-sputtering three different targets: Cu, Sn and CdS. The resulting sulfurized Cu2CdSnS4 thin film shows large densely packed grains and has a band gap value of 1.4 eV and a hole mobility of 21.35 cm2 v−1 s−1. Thus, a Cu2CdSnS4 thin-film solar cell with a proof of concept power conversion efficiency of 1.14% was fabricated.

This paper proposes a new mechanism to explain the performance of thin dye-sensitized solar cells (DSSC). Near-stoichiometric flower-like Cu2ZnSnS4 (CZTS) microspheres with a high specific surface area was fabricated for use as the photocathode in a DSSC. To improve the extraction and transfer of electrons, graphene was added to the CZTS. A DSSC with a 10-μm TiO2 photoanode layer exhibited a slightly degraded efficiency with a CZTS–graphene photocathode, relative to a Pt counter electrode (CE). Nevertheless, when the thickness of the TiO2 photoanode was reduced to 2 μm, the efficiency of a DSSC with a CZTS–graphene photocathode was greater than that of a Pt-DSSC. It is speculated that, unlike the Pt CE, a CZTS–graphene photocathode not only collects electrons from an external circuit and catalyzes the reduction of the triiodide ions in the electrolyte, but also utilizes unabsorbed photons to produce photo-excited electrons and suppresses charge recombination, thus enhancing the performance of the cell. The use of narrow band gap p-type semiconductors as photocathodes offers a new means of fabricating thin dye-sensitized solar cells and effectively improving the cell performance.本文采用一种新的机理解释薄的染料敏化太阳能电池的性能。采用接近计量比、具有较大比表面积的花状铜锌锡硫微球作为染料敏化太阳能电池的光阴极。为了提高电子的提取和转移,本文在铜锌锡硫微球中加入了2%wt石墨烯,同时选取不同厚度(2–10微米)的二氧化钛光阳极,研究铜锌锡硫-石墨烯光阴极对电池性能的影响。随着光阳极厚度的降低,以铜锌锡硫-石墨烯作为光阴极的染料敏化太阳能电池具有较好的光电转换效率。研究发现,铜锌锡硫-石墨烯作为光阴极不仅可以从外部电路收集电子和催化还原电解液中的三价碘离子,而且通过利用未被吸收的光子产生光激发电子可以有效抑制电子的复合,从而提高电池的光电转换效率。选用窄带隙的P型半导体作为光阴极材料为薄的染料敏化太阳能电池的制备及其电池性能的提高提供了一种新的思路。

•Rate performance of the battery was significantly enhanced by the gel-binder.•Stability of the Li–S battery was significantly enhanced by the gel-binder.•The gel-binder could decrease the charge transfer resistance of the battery.A Li ion conductive gel-binder, Li ion-doped 1,3-dichloro-2-propanol-sulfur-poly(ethylene glycol) methyl ether binder, was employed on the S cathode to enhance the rate performance of the Li/S battery. The reversible capacity of such batteries is 690 mAh g− 1 at a 3 C-rate after 27 cycles, and it reverts to 1020 mAh g− 1 at 0.2 C-rate, which is close to the initial value of 1210 mAh g− 1. Besides, at 0.5 C-rate, the battery with this gel-binder shows a high initial specific capacity of 976 mAh g− 1 and retains a capacity of 560 mAh g− 1 for more than first 500 cycles.The Li ion conductive gel-binder (PS(DCP-PEG)/Li+) efficiently imparts better rate performance to Li/S batteries than the PVDF and CMC. A battery with PS(DCP-PEG)/Li+ showed reversible capacities of 690 mAh g− 1 at 3 C-rate. Further cycling at 0.2 C-rate reinstates a reversible capacity of 1020 mAh g− 1 for the next three cycles, which is close to the initial capacity of 1210 mAh g− 1.

Organohalogen perovskites are attracting considerable attention for use in solar cells. However, the stability of these devices will determine whether they can be made commercially viable. Device encapsulation or the use of a hydrophobic hole-transporting material can prevent the permeation of water into the perovskite layer and enhance the humidity stability of the cells under dark conditions. With regard to the light stability of solar cells, recent studies have yielded contradictory results. This work investigated the degradation mechanism of perovskite solar cells under illumination. Further, a simple method was proposed for improving their illumination stability. Amino acids were inserted between the compact TiO2 layer and the perovskite layer to effectively prevent the decomposition of the perovskite layer owing to the superoxide anions and hydroxyl radicals generated under illumination from the H2O and O2 adsorbed onto the TiO2 layer.有机/无机杂化钙钛矿材料因在太阳能电池中的使用而备受关注。目前电池的稳定性是决定其产业化的关键问题。钙钛矿太阳能电池通过封装或利用疏水空穴传输层来避免钙钛矿材料与水接触,从而提高无光照下电池的稳定性。但对于钙钛矿电池的光照稳定性,最新研究结果存在互相矛盾之处。本文研究了光照下有机/无机杂化钙钛矿材料的分解机理,并提出了一个简单的方法来提高钙钛矿电池的光照稳定性,即在致密二氧化钛层和钙钛矿层中间引入氨基酸盐酸盐。研究结果表明,二氧化钛表面吸附的少量水、氧在光照下会产生超氧阴离子和氢氧自由基,氨基酸盐酸盐的引入避免了钙钛矿层与TiO2层接触而发生分解。

For the successful commercialization of organic–inorganic halide perovskite solar cells, it is necessary to ensure their stability in addition to high efficiency. In this study, the degradation mechanism of organic–inorganic halide structures in humidity was investigated computationally. Owing to the high polarity of water molecules, the unprotected organic–inorganic structure will inevitably decompose in a humid environment. To improve the ambient stability of the organic–inorganic perovskite solar cells, we introduced an interface modification method using ultrathin compact aluminum oxide (Al2O3) layers deposited by atomic layer deposition (ALD). The experimental results showed the ambient stability of the organic–inorganic perovskite solar cell with an ultrathin compact Al2O3 layer was greatly improved without a significant reduction in efficiency.

•30-μm-thick Si substrates are employed to fabricate ultrathin IBC solar cells.•Improvement in light-trapping is observed when increasing the lengths of Si NWs.•15-nm-thick Al2O3 coating shows the most competitive passivation performance.•A conversion efficiency of 16.61% was determined for 30 μm-thick IBC cell.With the very high efficiency that has been achieved in silicon-based solar cells, the international technology roadmap for photovoltaics foresees a steady decrease in the thicknesses of such cells over the next decade. In this paper, we present an ultrathin interdigitated back-contacted silicon solar cell fabricated using 30-μm-thick Si substrates. In consideration of the special light-trapping and passivation requirements for ultrathin wafers, Si nanowire arrays coated with Al2O3 were used to significantly reduce the reflectance in the visible region of the solar spectrum. The 15-nm-thick conformal Al2O3 coating improved the effective minority carrier lifetime of the silicon nanowires and exhibited competitive passivation performance. Furthermore, the photovoltaic properties of the fabricated ultrathin solar cell were investigated and a relatively high conversion efficiency of 16.61% was determined for a thickness of 30 μm. The findings of this study confirm the feasibility of producing ultrathin silicon-based photovoltaic devices.

As solar cell structures based on planar heterojunctions have already demonstrated very impressive advances in cost-effectiveness and performance, many different solvents are being developed and gradually adopted for high-performance inorganic–organic hybrid perovskite solar cells. Here, we introduce a simple planar cell configuration with layers prepared in a fully solution-based process, in which dimethylacetamide (DMAC) serves as an effective precursor solvent that is comparable with N,N-dimethylformamide (DMF). The use of DMAC leads to a smooth and dense perovskite film via one-step deposition, whose ideal morphology enables solar cells to obtain a high power-conversion efficiency of 15.12%. We also studied the effect of different solvents through a computation of the stabilization energy between PbI2, CH3NH3I, and solvent molecules. These results offer insight into the promising directions for the development of solvent engineering.

Because organic–inorganic perovskite solar cells are known to be unstable in the presence of moisture, most of the reported high-efficiency perovskite solar cells are fabricated under an inert atmosphere in a glove box. This requirement impedes mass production of organic–inorganic perovskite solar cells (PVSCs). Fabricating dense uniform perovskite thin films with high surface coverage via a single one-step solution process is also a challenge in achieving high-efficiency PVSCs. In this work, we successfully develop a facile, controllable one-step solution processing method to obtain high-quality hybrid-perovskite thin films in ambient atmosphere. The entire preparation process for CH3NH3PbI3 films is conducted in ambient air to investigate the effect of humidity on the molecular structure and crystallization of the hybrid perovskite. It is found that relative humidity (RH) and solvent are crucial factors in determining the final morphology of CH3NH3PbI3 and the photovoltaic performance. The best device efficiency achieved for a solar cell fabricated in ambient atmosphere under a RH of 28% is 16.15%; this PCE value is comparable to that of glove box-based PVSCs. This work puts forth a possible method for the easy mass production of high-performance PVSCs under ambient conditions.

•High-quality polycrystalline BiFeO3 films have been of great interest for many electrical and optical applications, however the fabrication of polycrystalline BFO films offering a large remnant polarization and low leakage current are difficult. In this work, high quality polycrystalline BFO films were deposited using a simplified sputtering method. This is a considerable oversight, as ITO-coated glass is one of the most widely used substrates in industry, and sputtering technique is easily scaled up for mass production. By comparing the measurement results against those obtained with BFO films on FTO/glass and Pt/Ti/SiO2/Si substrates, it is found that choice of electrode material significantly affects the quality of the film. As a result, we found that ITO/glass substrate is more suitable for depositing high quality BFO films.•The remnant polarization and leakage current density of the poly-BFO films we made are comparable to those epitaxially grown on single crystalline substrates or deposited on Pt buffered Si substrates by pulsed laser deposition.•There have as yet been few studies pertaining to the ferroelectric properties of BFO films thinner than 240 nm, which can be achieved on an ITO substrate by sputtering. Moreover, there is still little understanding of the relationship between photovoltaic effect and ferroelectric properties of ultrathin BFO film with different thickness. We found that film quality was highly dependent on the film thickness, with a thinner film displaying greater leakage. Despite the degradation in ferroelectric performance, however, the photovoltaic response was enhanced due to an enhanced depolarization field and shortened migration distance. Ultrathin BFO films therefore broaden the potential applications for ferroelectric photovoltaic devices by improving their carrier mobility, and allow for fine-tuning of their band structure when combined with semiconductors and electrodes.High-quality polycrystalline BiFeO3 (BFO) films have been of great interest for many electrical and optical applications, however the fabrication of polycrystalline BFO films offering a large remnant polarization and low leakage current are difficult. In this work, polycrystalline BFO films were deposited using a radio frequency magnetron sputtering method. It was found that the remnant polarization of BFO deposited on ITO is about three and seventy times larger than films deposited on Pt and FTO, respectively. Film quality was highly dependent on the film thickness, with a thinner film displaying greater leakage. Despite the degradation in ferroelectric performance, however, the photovoltaic response was enhanced. Ultrathin BFO films therefore broaden the potential applications for ferroelectric photovoltaic devices by improving their carrier mobility, and allow for fine-tuning of their band structure when combined with semiconductors and electrodes.

ZnO nanowire or nanorod arrays have caused great interest owing to their unique properties and versatile applications in short-wavelength lasers, electroluminescent devices, photocatalytic systems, and solar cells, etc. The electrical and optical properties of ZnO nanorod arrays can be altered and controlled through doping. In this paper, B2H6 plasma treatment was employed to improve the electrical properties of ZnO nanorod arrays prepared by hydrothermal synthesis. A clear decrease in the resistivity of ZnO nanorod arrays with B2H6 plasma treatment was observed. Moreover, the measurement results of XPS and Hall measurement show that the B2H6 plasma treatment can be used to achieve n-type doping via B atoms substitution for Zn atoms.

•Resistance of nanometer-thick Cu film was sensitive to deposition temperature.•Optimal temperature deposition was determined to obtain low-resistivity.•Critical thickness at which Cu films exhibit continuous growth was determined.•Resistivity reduced with annealing at 300–350 °C.Because of the superior properties of copper, it has been of great interest as a conducting material to replace aluminum in device manufacturing. In this study, we investigated the influence of substrate temperature, film thickness, and rapid thermal annealing (RTA) on the deposition of Cu films of thickness less than 10 nm. Compared to thicker films, the electrical properties of nanometer-thick films were found to be very sensitive to the deposition temperature. Further, we determined the optimal deposition temperature to obtain low-resistivity nanometer-thick Cu films. The Cu films were deposited with island-type growth, and the interconnection between grains plays a major role in the resistivity of the films. We also determined the critical thickness at which Cu films exhibit continuous growth as 8 nm. After RTA, the film color darkened, electron scattering became weak, and the resistivity reduced more than 20% with annealing at 300–350 °C, because of the growth of Cu grains. The results of this study indicate that thermal ALD can be used in conjunction with RTA to produce low-resistivity Cu thin films, the thickness, uniformity, and conformality of which can be easily controlled.

ZnO films deposited by atomic layer deposition at 70 °C were used to fabricate perovskite solar cells, and a conversion efficiency of 13.1% was obtained. On the ZnO layer, CH3NH3PbI3 was formed at room temperature using CH3NH3I and PbCl2 precursors, which is in contrast to the reported results.

•Addition of Im-SiO3/2 dramatically increased the H3PO4 doping capacity of the membranes.•The PA-doped hybrid membranes show the conductivity of 6.3 × 10−2 S cm−1 at 180 °C.•Im-SiO3/2 is effective in preventing the release of H3PO4 from the hybrid membranes.Phosphoric acid doped polybenzimidazole (PBI)/imidazolium-modified silsesquioxane (Im-SiO3/2) hybrid membranes with high proton conductivity at high temperature under anhydrous conditions are synthesized and characterized. The presence of Im-SiO3/2 is confirmed by FT-IR and energy-dispersive X-ray spectroscopy (EDS) mapping of silicon element. The phosphoric acid uptake and proton conductivity of the hybrid membranes increase with the Im-SiO3/2 content, and the conductivity of PBI/Im-SiO3/2-20 reaching 6.3 × 10−2 S cm−1 at 180 °C. Compared with pure PBI membranes, the introduction of Im-SiO3/2 is effective in preventing the release of the phosphoric acid component from the hybrid membranes. The properties of the prepared hybrid membranes indicate their promising prospects in anhydrous proton exchange membrane applications.

Ionic liquid-tethered graphene oxide (IL-GO) are prepared by tethering 1-(3-aminopropyl)-3-methylimi-dazolium bromide to graphene oxide (GO), and followed by anion-exchange with bis(trifluoromethanesulfonyl)imide ions (TFSI−). Environmental friendly ionic liquid-based composite electrolyte for dye sensitized solar cells (DSSCs) without volatile organic solvents is prepared from IL-GO and 1-propyl-3-methylimidazolium iodide (PMII). Incorporation of proper amount of IL-GO significantly increased the conductivity of the electrolyte, the open circuit voltage, the short circuit current density and the conversion efficiency of DSSCs. The dye-sensitized solar cells (DSSCs) containing 4 wt% of IL-GO composite electrolytes show an overall power conversion efficiency of 7.04% under simulated AM 1.5 solar spectrum irradiation at 100 mW cm−2. These results indicate that the DSSCs based on IL-GO/IL composite electrolytes could overcome the drawbacks of volatile liquid electrolytes, and offer a feasible method to fabricate DSSCs in future practical applications.

•180 μm thick p-type Si was used to fabricate AZO/Si:H(n)/a-Si:H/c-Si(p) nanowire solar cells.•JSC was increased by 16.2% when an n-type Si:H layer changed from amorphous to a double phase structure.•Controlling the Al2O3 thickness played a key role in balancing the passivating and tunneling effects.•With 0.77-nm-thick Al2O3, JSC and η were increased by 10.2% and 6.8%, respectively.In this work, p-type solar-grade Si (100) wafers with a thickness of 180 μm were used to fabricate Al-doped ZnO(AZO)/n-type Si:H/i-Si:H/c-Si(p) nanowire (NW) array solar cells in which the Si:H and Al2O3 layers were deposited by plasma-enhanced chemical deposition and atomic layer deposition, respectively. To realize a good coverage of Si:H layers on the Si NWs, excessively thin Si:H layers were avoided. Moreover, since the NW array gives rise to significant light trapping, the light absorption by the Si:H layers could not be neglected. It is known that compared to amorphous Si:H, the charge mobility and light absorption are improved in the two-phase Si:H with nanocrystalline grains dispersed in the amorphous matrix. Therefore, it is important to investigate the influence of the microstructures of n-type Si:H on the performance of solar cells. On the other hand, in contrast to the Al2O3 passivation of planar Si solar cells, in this study, ultrathin Al2O3 layers were deposited on Si NWs without post-deposition annealing. We also discuss the passivation behavior of these ultrathin Al2O3 layers on n-type Si:H and the balance between the surface passivation and the role of these layers as tunnel barriers.

•Two strategies were employed to enhance the dye adsorption of ZnO nanorod-based DSSCs.•The density of the nanorod arrays increased with increasing the thickness of ZnO seed layers.•The adsorption saturated after 4 cycles of desorption/adsorption process.•An approximately 100% increase in conversion efficiency is achieved.A critical factor in enhancing the conversion efficiency of ZnO nanorod array-based dye-sensitized solar cells (DSSCs) is the dye adsorption, which is determined by the dye adsorptivity of single nanorod and the density of nanorod arrays. We show that the density of the nanorod arrays increases gradually with increasing seed layer thickness, resulting in an enlarged surface area for dye adsorption. In addition, increasing the number of desorption/adsorption cycles can also lead to a continuous increase in the total amount of dye loading. As a result, we observe a significant enhancement in the photocurrent densities and conversion efficiencies of ZnO nanorod array-based DSSCs.

•The sandwich structural CoS/graphene sheet electrode was prepared.•The graphene plays a key role in modifying the nanostructure of the electrode.•The CoS/GS electrode possesses excellent electrochemical property.•The quantum dot-sensitized solar cell shows an improved photovoltaic property.A sandwich structural CoS/graphene sheet (CoS/GS) electrode was prepared by repeating electrophoretic deposition of graphene sheets and deposition of CoS nanoparticles. We found the graphene sheets play a key role in controlling the morphology of the nanostructure. The obtained CoS/graphene nanocomposite counter electrode has a high specific surface area and displays an excellent electrochemical activity toward the polysulfide electrolyte. Consequently, the quantum dot-sensitized solar cell based on CoS/GS counter electrode shows an improved photovoltaic performance.

•PBI/ZC-PAMAM dendrimer (containing sulfonic acid and amine groups) composite membranes was synthesized for DMFC applications.•Water uptake and ionic conductivity results showed good prospects for use in DMFC.•The methanol permeability of PBI/ZC-PAMAM composite membranes is much lower than that of Nafion-117.The zwitterion-coated polyamidoamine (ZC-PAMAM) dendrimer with ammonium and sulfonic acid groups has been synthesized and used as filler for the preparation of PBI-based composite membranes for direct methanol fuel cells. Polybenzimidazole (PBI)/ZC-PAMAM dendrimer composite membranes were prepared by casting a solution of PBI and ZC-PAMAM dendrimer, and then evaporating the solvent. The presence of ZC-PAMAM dendrimer was confirmed by FT-IR and energy-dispersive X-ray spectroscopy (EDS) mapping of sulfur and oxygen elements. The water uptake, swelling degree, proton conductivity, and methanol permeability of the membranes increased with the ZC-PAMAM dendrimer content. For the PBI/ZC-PAMAM-20 membrane with 20 wt% of ZC-PAMAM, it shows a proton conductivity of 1.83 × 10−2 S/cm at 80 °C and a methanol permeability of 5.23 × 10−8 cm2 s−1. Consequently, the PBI/ZC-PAMAM-20 demonstrates a maximum power density of 26.64 mW cm−2 in a single cell test, which was about 2-fold higher than Nafion-117 membrane under the same conditions.

Organohalogen perovskites are attracting considerable attention for use in solar cells. However, the stability of these devices will determine whether they can be made commercially viable. Device encapsulation or the use of a hydrophobic hole-transporting material can prevent the permeation of water into the perovskite layer and enhance the humidity stability of the cells under dark conditions. With regard to the light stability of solar cells, recent studies have yielded contradictory results. This work investigated the degradation mechanism of perovskite solar cells under illumination. Further, a simple method was proposed for improving their illumination stability. Amino acids were inserted between the compact TiO2 layer and the perovskite layer to effectively prevent the decomposition of the perovskite layer owing to the superoxide anions and hydroxyl radicals generated under illumination from the H2O and O2 adsorbed onto the TiO2 layer.

This paper proposes a new mechanism to explain the performance of thin dye-sensitized solar cells (DSSC). Near-stoichiometric flower-like Cu2ZnSnS4 (CZTS) microspheres with a high specific surface area was fabricated for use as the photocathode in a DSSC. To improve the extraction and transfer of electrons, graphene was added to the CZTS. A DSSC with a 10-μm TiO2 photoanode layer exhibited a slightly degraded efficiency with a CZTS–graphene photocathode, relative to a Pt counter electrode (CE). Nevertheless, when the thickness of the TiO2 photoanode was reduced to 2 μm, the efficiency of a DSSC with a CZTS–graphene photocathode was greater than that of a Pt-DSSC. It is speculated that, unlike the Pt CE, a CZTS–graphene photocathode not only collects electrons from an external circuit and catalyzes the reduction of the triiodide ions in the electrolyte, but also utilizes unabsorbed photons to produce photo-excited electrons and suppresses charge recombination, thus enhancing the performance of the cell. The use of narrow band gap p-type semiconductors as photocathodes offers a new means of fabricating thin dye-sensitized solar cells and effectively improving the cell performance.

ZnO films deposited by atomic layer deposition at 70 °C were used to fabricate perovskite solar cells, and a conversion efficiency of 13.1% was obtained. On the ZnO layer, CH3NH3PbI3 was formed at room temperature using CH3NH3I and PbCl2 precursors, which is in contrast to the reported results.

Organic–inorganic halide perovskites have emerged as attractive materials for use in photovoltaic cells. Owing to the existence of dangling bonds at the grain boundaries between perovskite crystals, minimizing the charge recombination at the surface or grain boundaries by passivating these trap states has been identified to be one of the most important strategies for further optimization of device performance. Previous reports have mainly focused on surface passivation by inserting special materials such as graphene or fullerene between the electron transfer layer and the perovskite film. Here, we report an enhanced efficiency of mesoscopic perovskite solar cells by using graphene quantum dots (GQDs) to passivate the grain boundaries of CH3NH3PbI3. The highest efficiency (17.62%) is achieved via decoration with 7% GQDs, which is an 8.2% enhancement with respect to a pure perovskite based device. Various analyses including electrochemical impedance spectroscopy, time-resolved photoluminescence decay and open-circuit voltage decay measurements are employed in investigating the mechanism behind the improvement in device performance. The findings reveal two important roles played by GQDs in promoting the performance of perovskite solar cells – that GQDs are conducive to facilitating electron extraction and can effectively passivate the electron traps at the perovskite grain boundaries.

Balancing the high power conversion efficiency (PCE) and long-term stability of organic–inorganic hybrid perovskite solar cells (Pero-SCs) is a challenging factor for the commercialization of solar cells. Herein, a cost-effective and widely available water-soluble additive, polyvinyl alcohol (PVA), has been adopted to improve the film quality of CH3NH3PbI3 and enhance the efficiency and long-term tolerance to humidity. A PCE of 17.4% has been achieved for the device with PVA, showing an 11.6% increase compared to those of the devices without the additive. Most importantly, the unencapsulated devices retain over 90% of their initial efficiency even after 30 days in a high humidity environment (90% relative humidity), exhibiting greater humidity tolerance and superior stability. Our studies present a simple solution-based approach to fabricate high efficiency solar cells with long-term stability under high humidity conditions, potentially revealing new methods for the mass production of Pero-SCs.

Tandem solar cells combining a wide bandgap, efficient perovskite absorber with a low bandgap photovoltaic module, such as a c-Si cell, can potentially achieve a high theoretical efficiency of over 30%. Instead of using the conventional parallel stacking tandem, we report here a reflective tandem configuration, with the perovskite solar cell acting as the spectral filter that absorbs high energy photons, while sub-bandgap photons are reflected to a Si sub-cell using a highly reflective back metal electrode. The perovskite solar cell exhibits a high reflectance of over 60% in the near infrared spectral region, which allows the subsequent silicon cell to absorb photons in this region, resulting in a high current density of 13.03 mA cm−2. In such a tandem configuration, we achieved a combined efficiency of 23.1% using a four-terminal measurement. This result demonstrates the promise of employing perovskite solar cells in a reflective tandem for a high efficiency solar energy conversion system, with an efficiency of up to 30%.

One of the main issues for high-performance perovskite solar cells (PSCs) is the fabrication of high-quality perovskite films. However, a thermal annealing process is generally required for a high crystallinity film via a typical solution-based method, which may result in inhomogeneous nucleation, and is time-consuming. Herein, we investigate the effects of different solvents on the morphology and the crystallinity of perovskite films systematically and further develop a solvent-technique for uniform perovskite films without the need for annealing. N-Methyl-2-pyrrolidone (NMP) has been adopted as a high-boiling-point solvent and a complexant, combined with the commonly used N,N-dimethylformamide (DMF) or dimethylacetamide (DMAc), to improve the quality of perovskite films and enhance the corresponding device performance. PSCs fabricated from DMAc/NMP co-solvents using the post-annealing process show the best power conversion efficiency (PCE) of 17.38%, which is about 10% improvement compared to that of the device based on DMF/dimethyl sulfoxide (DMSO) or DMAc/DMSO co-solvents. Notably, 17.09% efficiency has been achieved even without any post-annealing process for the device based on DMAc/NMP co-solvents. However, only 3.81% efficiency can be obtained for the device based on DMAc/DMSO co-solvents under the same conditions. The observed phenomenon is mainly due to the fact that the NMP-included solvents can induce an instant crystallization once the anti-solvent drips on the films at room temperature (RT). Our study may provide a new approach to prepare high-quality perovskite films at RT, which would simplify the fabrication procedures and reduce the cost of efficient PSC manufacture.

For the successful commercialization of organic–inorganic halide perovskite solar cells, it is necessary to ensure their stability in addition to high efficiency. In this study, the degradation mechanism of organic–inorganic halide structures in humidity was investigated computationally. Owing to the high polarity of water molecules, the unprotected organic–inorganic structure will inevitably decompose in a humid environment. To improve the ambient stability of the organic–inorganic perovskite solar cells, we introduced an interface modification method using ultrathin compact aluminum oxide (Al2O3) layers deposited by atomic layer deposition (ALD). The experimental results showed the ambient stability of the organic–inorganic perovskite solar cell with an ultrathin compact Al2O3 layer was greatly improved without a significant reduction in efficiency.