Tin dioxide (SnO2) has been demonstrated as an effective electron-transporting layer (ETL) for attaining high-performance perovskite solar cells (PSCs). However, the numerous trap states in low-temperature solution processed SnO2 will reduce the PSCs performance and result in serious hysteresis. Here, we report a strategy to improve the electronic properties in SnO2 through a facile treatment of the films with adding a small amount of graphene quantum dots (GQDs). We demonstrate that the photogenerated electrons in GQDs can transfer to the conduction band of SnO2. The transferred electrons from the GQDs will effectively fill the electron traps as well as improve the conductivity of SnO2, which is beneficial for improving the electron extraction efficiency and reducing the recombination at the ETLs/perovskite interface. The device fabricated with SnO2:GQDs could reach an average power conversion efficiency (PCE) of 19.2 ± 1.0% and a highest steady-state PCE of 20.23% with very little hysteresis. Our study provides an effective way to enhance the performance of perovskite solar cells through improving the electronic properties of SnO2.Keywords: electron transfer; electron traps; graphene quantum dots; perovskite solar cells; tin dioxide;

•We demonstrate for the first time the utilization of GQDs as an additive to PCBM.•The device maintains ~80% of its PCE under continuous 300 h full spectrum sunlight.•GQDs: PCBM resulted in a high efficient (17.56%) PSC with negligible hysteresis.•All component layers are deposited at room temperature and treated below 100 °C.Organic-inorganic hybrid perovskite solar cells (PSCs) have triggered a great deal of research on organic electron transport layers, such as phenyl C61 butyric acid methyl ester (PCBM), due to their potential application as a strong contender in photovoltaic industry with simple fabrication process and low cost. However, the low electrical conductivity and electron mobility of PCBM hinder the promotion of PSCs. Here we report a successful case of graphene quantum dots (GQDs) doping into PCBM electron transport layer (ETL) of planar N-I-P PSCs, resulting in an obvious increase in PCBM conductivity together with the enhanced charge extraction and reduced the trap state density of perovskite films. A low doping ratio (0.5 wt%) would be efficient to boost the Voc, Jsc and FF, a PCE of 17.56% is achieved. More importantly, the light stability of PSCs with PCBM: GQDs was improved: the unpackaged cells can keep > 80% of the initial PCE under simulated sunlight with the full UV component present after 300 h, in contrast to the reference device that dropped < 50% during the same period of time.Download high-res image (196KB)Download full-size image

In this Communication, a self-organization method of [6,6]-phenyl-C61-butyric acid 2-((2-(dimethylamino)-ethyl) (methyl)amino)ethyl ester (PCBDAN) interlayer in between 6,6-phenyl C61-butyric acid methyl ester (PCBM) and indium tin oxide (ITO) has been proposed to improve the performance of N–I–P perovskite solar cells (PSCs). The introduction of self-organized PCBDAN interlayer can effectively reduce the work function of ITO and therefore eliminate the interface barrier between electron transport layer and electrode. It is beneficial for enhancing the charge extraction and decreasing the recombination loss at the interface. By employing this strategy, a highest power conversion efficiency of 18.1% has been obtained with almost free hysteresis. Furthermore, the N–I–P PSCs have excellent stability under UV-light soaking, which can maintain 85% of its original highest value after 240 h accelerated UV aging. This self-organization method for the formation of interlayer can not only simplify the fabrication process of low-cost PSCs, but also be compatible with the roll-to-roll device processing on flexible substrates.

Boron-oxygen defects can cause serious light-induced degradation (LID) of commercial solar cells based on the boron-doped crystalline silicon (c-Si), which are formed under the injection of excess carriers induced either by illumination or applying forward bias. In this contribution, we have demonstrated that the passivation process of boron-oxygen defects can be induced by applying forward bias for a large quantity of solar cells, which is much more economic than light illumination. We have used this strategy to trigger the passivation process of batches of aluminum back surface field (Al-BSF) solar cells and passivated emitter and rear contact (PERC) solar cells. Both kinds of the treated solar cells show high stability in efficiency and suffer from very little LID under further illumination at room temperature. This technology is of significance for the suppression of LID of c-Si solar cells for the industrial manufacture.

•Silicon powder coating was brushed on crucible wall.•Small grains were formed at the ingot edge.•The diffusion of Fe from Si3N4 was obviously depressed.•The width of “red zone/ black edge” was well reduced.•The solar cell efficiency of edge bricks was improved.The high performance multicrystalline (HPMC) silicon material with the feature of small and uniform grains has already been widely adopted in photovoltaic industry nowadays. However, the HPMC silicon ingots still suffer a comparatively lower minority carrier lifetime at the ingot edges induced by Fe in-diffusion. Here, we have engineered the grain boundaries (GBs) to control the low carrier lifetime zone at the HPMC silicon ingot edges, based on the grain nucleation enhanced by silicon powder coating at the crucible walls. The resultant GBs with high density paralleling to the crucible walls can getter Fe impurity, and meanwhile become the barriers for Fe diffusion. Therefore, the detrimental effect of interstitial Fe impurity on the carrier lifetime of edge wafers is sufficiently reduced and the performance of corresponding solar cells is improved. The solar cells have a narrower distribution in the performance, which is beneficial for the stability and durability of solar cells and modules. This growth concept using GBs to control the behaviors of Fe diffused from the crucible walls is interesting for photovoltaic application.

The determination of boron and phosphorus ionization energies in compensated silicon is very important for assessing the ionization level of dopants and their interaction with each other. In this paper, we achieved the boron and phosphorus ionization energies in compensated silicon by temperature-dependent luminescence for the first time. The results show that the boron and phosphorus ionization energies in heavily-compensated silicon have the same values as those in non-compensated silicon. This strongly suggests that both boron and phosphorus impurities with a concentration of ≤ 10 17 cm −3 should act as isolated acceptors and donors, but do not form complexes in silicon.

•The formation of metastable vacancy-dioxygen (VO2) complex in silicon, with a structure of [VO + Oi] is quantitatively investigated, which has little been experimentally reported.•Combined with the evolution of interstitial oxygen and VO complex during annealing, the mechanisms for [VO + Oi] formation and VO annihilation have been discussed.We have quantitatively investigated the formation kinetics of metastable vacancy-dioxygen (VO2) complex in a structure of [VO + Oi], where a VO complex is trapped in a next-neighbor position to an interstitial oxygen atom (Oi). It is found that the VO annihilation is accompanied by the generation of metastable [VO + Oi] complex during annealing in the temperature range of 220–250 °C. The activation energy for [VO + Oi] generation appears at around 0.48 eV, which is much lower than the counterpart of stable VO2 complex. This indicates that the formation of [VO + Oi] complex originates from the reaction between VO and Oi. The ab initio calculations show that the formation energy of [VO + Oi] complex is larger than that of VO2 complex, which means that [VO + Oi] complex is thermodynamically unfavorable as compared to VO2 complex. However, the binding energy of [VO + Oi] complex is positive, indicating that [VO + Oi] complex is stable against decomposition of VO and Oi in silicon. It is believed that [VO + Oi] complex serves as the intermediate for VO to VO2 conversion.Download high-res image (292KB)Download full-size image

Graphene/silicon (Gr/Si) solar cells have attracted extensive research interest for their potentials in low-cost photovoltaic applications. However, the performance of Gr/Si solar cells is still limited by the working principles of Schottky junctions. This work developed a new type of Gr/Si solar cell with a self-generated quasi p–n junction. In such devices, a strong upward band bending is caused by considerable charge transfer from Si, resulting in a p-type layer being formed at the near-surface of the n-type Si substrate. They have similar rectification characteristics to conventional p–n junctions, and are even superior due to the absence of the “dead layer”. Here, a thermal evaporation deposited tungsten tri-oxide (WO3) interlayer was inserted between the Gr and Si to form the quasi p–n junction Gr/Si solar cells, achieving a high power conversion efficiency (PCE) of 10.59% for Gr/Si solar cells without chemical doping. The concept of a self-generated quasi p–n junction offers a possibility to overcome the limitations affecting the development of Gr/Si solar cells, and shows a promising future for diverse transition metal oxides for the fabrication of low-cost, high-efficiency and stable photovoltaic devices in the future.

Graphene/silicon (Gr/Si) solar cells have attracted interest for their potential in low-cost photovoltaic applications. Inserting a p-type organic hole transporting layer (HTL) in-between the Gr and Si would suppress carrier recombination and improve the performance of the solar cells. Here, we report highly stable and high-performance Gr/Si solar cells fabricated by using a room-temperature process. Spiro-OMeTAD was selected as the HTL for its novel electrical and optical properties. The employment of spiro-OMeTAD led to an impressive power conversion efficiency (PCE) of 13.02%. Moreover, our solar cells exhibit excellent stability with a PCE of ∼11% for over four months. These results could be encouraging for the development of Gr/Si solar cells toward practical applications. Meanwhile, this work offers a universal solution for the application of organics in Gr-based optoelectronics and photovoltaics from the viewpoint of device robustness.

Considering the evaporation of solvents during fabrication of perovskite films, the organic ambience will present a significant influence on the morphologies and properties of perovskite films. To clarify this issue, various ambiences of N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and chlorobenzene (CBZ) are introduced during fabrication of perovskite films by two-step sequential deposition method. The results reveal that an ambient CBZ atmosphere is favorable to control the nucleation and growth of CH3NH3PbI3 grains while the others present a negative effect. The statistical results show that the average efficiencies of perovskite solar cells processed in an ambient CBZ atmosphere can be significantly improved by a relatively average value of 35%, compared with those processed under air. The efficiency of the best perovskite solar cells can be improved from 10.65% to 14.55% by introducing this ambience engineering technology. The CH3NH3PbI3 film with large-size grains produced in an ambient CBZ atmosphere can effectively reduce the density of grain boundaries, and then the recombination centers for photoinduced carriers. Therefore, a higher short-circuit current density is achieved, which makes main contribution to the improvement in efficiency. These results provide vital progress toward understanding the role of ambience in the realization of highly efficient perovskite solar cells.Keywords: ambience; grain growth; morphology; perovskite solar cells; reproducibility

•C co-doping will deteriorate the initial performance of Si solar cells.•C co-doping can suppress the B-O complex formation in crystalline silicon.•The C co-doped Si solar cell has better performances after full LID.•The C co-doped Si solar cells with low LID can be practically used in industry.We have investigated the impact of carbon co-doping on the performance of boron–doped Czochralski-grown silicon solar cells. It is found that carbon co-doping will deteriorate the initial performance of Aluminium-back-surface-field solar cells before light-induced degradation (LID), owing to the enhancement effect on the formation of oxygen precipitation. However, carbon co-doping can effectively suppress the formation of boron-oxygen complexes in the solar cells, which becomes more significant with an increase of the carbon concentration. Therefore, the performance of carbon co-doped silicon solar cells is better than that of conventional silicon solar cells after LID. All these results are of great significance for the practical application of carbon co-doped silicon solar cells with low LID effect in photovoltaic industry.

•The concentration range of Al doping is 0.01–0.1 ppmw.•The keff of Al in Si is obtained as 0.0029•Solar cell performance degrades with the increase of Al concentration.•Al doping shows no light induced degradation effect.•The efficiency of Al doped cell is comparable to that of degraded B doped cell.The impact of Al doping with the concentrations in the range of 0.01–0.1 ppmw on the performance of silicon wafers and solar cells is studied. The effective segregation coefficient of impurity keff of Al in Si is obtained as 0.0029, which is calculated as 0.0027, supporting that Al should be totally ionized and occupy the substitutional sites in silicon and serve as the +1 dopant. It is found that the open-circuit voltages (Uoc), short-circuit currents (Isc) and photo-electrical conversion efficiency of the Al-containing solar cells decrease with the increase of Al concentrations because of Al-related deep level recombination centers. The average absolute efficiency of Al-doped silicon solar cells is 0.34% lower than that of Ga-doped-only cells, and the largest difference can be about 0.62%. Moreover, Al doped silicon solar cells show no light induced efficiency degradation, and the average efficiency maintains above 17.78%, which is comparable at the final state to that of normal B-doped silicon solar cells.

•Impact of annealing process on the GrSi interface properties and device performances has been studied.•GrSi solar cells with Hydrogen, methyl group and native oxide terminated Si has been compared.•Multi kinds of Si surface passivation using Al2O3 and graphene oxide have been studied.•GrSi solar cells with MIS-like structures employing P3HT and MoS2 as the interlayer have been investigated.Graphene has attracted great research interests due to its unique mechanical, electrical and optical properties, which opens up a huge number of opportunities for applications. Recently, Graphene-Silicon (GrSi) solar cell has been recognized as one interesting candidate for the future photovoltaic. Since the first GrSi solar cell reported in 2010, GrSi solar cell has been intensively investigated and the power converse efficiency (PCE) of it has been developed to 15.6%. This review presents and discusses current development of GrSi solar cell. Firstly, the basic concept and mechanism of GrSi solar cell are introduced. Then, several key technologies are introduced to improve the performance of GrSi solar cells, such as chemical doping, annealing, Si surface passivation and interlayer insertion. Particular emphasis is placed on strategies for GrSi interface engineering. Finally, new pathways and opportunities of “MIS-like structure” GrSi solar cells are described.

•A highest PCE>17.2% has been achieved for the PSCs with PCBDAN.•The devices with PCBDAN show higher performance.•The improved stability of PSCs is related to the hydrophobic PCBDAN.•PCBDAN can be used in the fabrication of high efficient and stable PSCs.The recent rapid rise in power conversion efficiencies (PCEs) of perovskite solar cells (PSCs) has attracted worldwide extensive attention. However, the PSC applications are limited by their poor stability due to perovskite degradation in moisture. We used a fullerene amine interlayer in planar PSCs to reduce the interface barrier between ETL and metal electrode and also resist the moisture. The utilization of fullerene amine interlayer allowed for the enhancement of PSCs' performance, showing a highest power conversion efficiency (PCE)>17.2% with negligible hysteresis. More importantly, the air stability of PSCs with fullerene amine was improved: the unpackaged devices stored in air can keep their high performance with no obvious PCE loss in 10% humidity and >90% of the initial PCE in 45% humidity after 20 days.Improved performance and air stability of planar perovskite solar cells via interfacial engineering using a fullerene amine interlayer.

•We fabricated metal/insulator/semiconductor (MIS) solar cells with a structure of Gr/FG/Si.•Underside p-type Gr doping was obtained in the Gr/FG heterostructure.•One-step approach for doping and interface engineering of the Gr/Si solar cells was realized.•Performance of Gr/FG/Si solar cell was further enhanced by applying a temporary voltage bias.•PCE of 7.52% and 13.38% were achieved for the pristine Gr/FG/Si solar cell and after AR technique and chemical doping.One-step approach for doping and interface engineering of the Gr/Si solar cells was realized by using the fluorographene(FG) as an insulator interlayer. Metal/insulator/semiconductor (MIS) like solar cells with a structure of Gr/FG/Si were composed. The F atoms of FG serve as electron acceptors and yield p-type doping, which is beneficial for improving the Schottky barrier. The carrier recombination of the solar cell can be effectively suppressed by the employment of the FG interlayer and the PCE of the solar cell increased from 3.17% to 7.52%. More interestingly, the performance of Gr/FG/Si solar cell can be further enhanced by applying a temporary voltage bias, which was likely associated with rotation of the C―F bonds or/and enhancement of the Gr/FG coupling in electrical field. A PCE up to 13.38% was achieved by combining the AR technology and chemical doping from the top-side of the Gr.

Organic–inorganic halide perovskite solar cells have attracted great attention in recent years. But there are still a lot of unresolved issues related to the perovskite solar cells such as the phenomenon of anomalous hysteresis characteristics and long-term stability of the devices. Here, we developed a simple three-layered efficient perovskite device by replacing the commonly employed PCBM electrical transport layer with an ultrathin fulleropyrrolidinium iodide (C60-bis) in an inverted p-i-n architecture. The devices with an ultrathin C60-bis electronic transport layer yield an average power conversion efficiency of 13.5% and a maximum efficiency of 15.15%. Steady-state photoluminescence (PL) and time-resolved photoluminescence (TRPL) measurements show that the high performance is attributed to the efficient blocking of holes and high extraction efficiency of electrons by C60-bis, due to a favorable energy level alignment between the CH3NH3PbI3 and the Ag electrodes. The hysteresis effect and stability of our perovskite solar cells with C60-bis become better under indoor humidity conditions.Keywords: CH3NH3PbI3; electrical transport layer; fulleropyrrolidinium iodide; hysteresis effect; perovskite solar cells; stability;

Graphene–silicon (Gr-Si) heterojunction solar cells have been recognized as one of the most low-cost candidates in photovoltaics due to its simple fabrication process. However, the high sheet resistance of chemical vapor deposited (CVD) Gr films is still the most important limiting factor for the improvement of the power conversion efficiency of Gr-Si solar cells, especially in the case of large device-active area. In this work, we have fabricated a novel transparent conductive film by hybriding a monolayer Gr film with silver nanowires (AgNWs) network soldered by the graphene oxide (GO) flakes. This Gr-AgNWs hybrid film exhibits low sheet resistance and larger direct-current to optical conductivity ratio, quite suitable for solar cell fabrication. An efficiency of 8.68% has been achieved for the Gr-AgNWs-Si solar cell, in which the AgNWs network acts as buried contacts. Meanwhile, the Gr-AgNWs-Si solar cells have much better stability than the chemically doped Gr-Si solar cells. These results show a new route for the fabrication of high efficient and stable Gr-Si solar cells.Keywords: buried contact; graphene; silicon; silver nanowire; solar cell

Graphene–silicon (Gr–Si) Schottky junction solar cells have recently attracted intensive attention as candidates for low-cost photovoltaic devices. However, the efficiency of Gr–Si solar cells still needs further improvement. In this study, we have introduced an ultra-thin LiF layer between the Si and aluminum (Al) back electrode of Gr–Si solar cells. It is found that carrier recombination at the back surface is significantly suppressed, resulting directly in the improvement of external quantum efficiency (EQE) of devices in the long wavelength range of 800–1100 nm. Moreover, the back contact resistance is greatly reduced, and therefore the fill factor (FF) of devices is greatly improved. As a result, the highest power conversion efficiency (PCE) of 6.25% has been obtained for a pristine Gr–Si solar cell, which is further improved to 10.61% after chemical doping. These results pave a new way to the fabrication of high efficiency Gr–Si solar cells.

Graphene (Gr) film grown by the chemical vapor deposition (CVD) method has recently received intense attention in optoelectronic devices. As an alternative, the low cost graphene-oxide (GO) fabricated by a solution process is more promising for practical application. Here, we have fabricated a GO film on copper foil and then reduced it into a conductive film by high temperature annealing. It is found that the photoelectric properties of the reduced-graphene-oxide (r-GO) film are strongly dependent on the annealing temperature and film thickness. A thicker r-GO film under higher temperature annealing usually has better conductivity. By optimizing the reduction conditions of the GO films, the highest power conversion efficiency (PCE) of 3.36% can be achieved for a r-GO/Si solar cell. This value is currently the record efficiency for the r-GO/Si device architecture.

•The selective emitter structure is self-generated in the PEDOT:PSS/silicon solar cell by introducing a thin WO3 interlayer.•The contact resistance between Ag electrodes and PEDOT:PSS film is largely reduced.•The open-circuit voltage of PEDOT:PSS/silicon solar cell is significantly improved.•The PCE of solar cell with a WO3 interlayer is 11.5% higher than that of the reference ones.Organic/silicon hybrid solar cell has recently received intensive interest due to its simple and low-cost fabrication process, which could be potentially used in photovoltaics. However, the efficiency of organic/silicon solar cell needs further improvement. Here, we have introduced a WO3 thin layer between the Ag front electrodes and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)(PEDOT:PSS) film in the PEDOT:PSS/silicon solar cell to form a doping-free selective emitter (SE) structure. The carrier recombination is suppressed at the interface of silicon and electrodes, and meanwhile, the contact resistance between the Ag electrodes and PEDOT:PSS film is largely reduced. Therefore, the open-circuit voltage and fill factor of solar cell is significantly improved. As a result, the solar cell with a SE structure displays the power conversion efficiency (PCE) of 11.65%, which is much higher than the one without a WO3 thin layer. These results pave a new way for the fabrication of high efficiency organic/silicon hybrid solar cells.An 11.65% efficiency has been achieved for the PEDOT:PSS/silicon solar cell with doping-free selective emitter due to the introduction of a thin WO3 interlayer.

Graphene-on-silicon (Gr–Si) heterojunction solar cells have recently attracted significant attention as promising candidates for low-cost photovoltaic applications. However, the power conversion efficiency of Gr–Si solar cells is generally smaller than 4% without chemical doping treatments. It is mainly limited by the low work function of Gr and high density defect states at the Gr–Si interface. Here, we have reported a new structure of Gr–Si solar cells by introducing a graphene oxide (GO) interlayer to engineer the Gr–Si interface for improving device performance. It is found that the GO interlayer can effectively increase open circuit voltage and meanwhile suppress the interface recombination of solar cells. As a result, a maximum efficiency of 6.18% can be achieved for the Gr/GO/Si solar cells, which is a new record for the pristine monolayer Gr–Si solar cell reported to date. Further, it is clarified that the Gr/GO/Si solar cell is significantly more stable than the Gr–Si solar cell with chemical doping. These results show a new route for fabricating efficient and stable chemical-doping-free Gr–Si solar cells.

•At low irradiance intensity, the compensated cells generate less electricity.•At high temperature, the compensated cells generate more electricity.•The compensated cells will be more appropriate for high irradiation application.Low-cost upgraded metallurgical grade silicon (UMG-Si) with inherent boron (B) and phosphorus (P) compensation is a novel material for photovoltaic application. This paper presents the impact of solar irradiance intensity and temperature on the performance of compensated crystalline silicon solar cells. For the same rated output power, compensated crystalline silicon solar cells generate less electricity than the reference silicon solar cells at low irradiance intensity, owing to the strong injection dependence of the carrier lifetime due to high concentration of B–O complexes in compensated silicon. However, at high temperature, compensated crystalline silicon solar cells generate more electricity than the reference silicon solar cells, which mainly originates from the lower temperature-variation of the minority electron mobility in compensated silicon. It suggests that compensated silicon solar cells will be more appropriate for high irradiation application, which often contains high irradiance intensity and high temperature. These results are of great significance for understanding the actual outdoor performance of the solar cells based on the UMG-Si and their application in the photovoltaic (PV) industry.

•The light-induced degradation of p-type compensated Si solar cells is presented.•The minority carrier diffusion length can be recovered by deactivation treatment.•The compensated Si solar cell efficiency is increased by more than 3% absolutely.•Boron should be dirsectly involved in the generation and deactivation of B–O defects.Low-cost upgraded metallurgical grade silicon (UMG-Si) with inherent boron (B) and phosphorus (P) compensation is a novel material for photovoltaic application. In this study, we demonstrate the negative impact of the light-induced degradation (LID) on the efficiency of p-type UMG-Si solar cells. By a following illumination at elevated temperatures, the LID effect in the compensated silicon solar cells can be fully deactivated, and the minority carrier diffusion length is recovered to the original level. The conversion efficiency of the compensated silicon solar cells is increased by a value of more than 3% absolutely compared to the degraded state and is quite stable under the following illumination at room temperature. It is shown that both the boron–oxygen defect density and deactivation energy mainly depend on the total boron concentration rather than the net doping concentration, which strongly suggests that boron is directly involved in the generation and deactivation of boron–oxygen defect at the solar cell level. These results are of significance for understanding the LID effect of the solar cells based on low cost UMG-Si.

•Pt NPs coupled with Gr double the efficiency of Gr-Si solar cells.•Enhancement of Pt NPs comes from their plasmonic effect and physical doping abilityon Gr.•The photo-induced doping of Pt NPs on Gr is firstly reported on Gr-Si solar cells.•The coupling of Pt NPs is air-stable and antireflection-coating-compatible.Graphene-silicon (Gr-Si) solar cells have been intensively investigated in recent years, which exhibits a potential application of two-dimensional materials in photovoltaics. However, the pristine Gr with low carrier concentration and therefore low work function is not suitable for the fabrication of high performance solar cells. Chemical doping is an effective way to improve the carrier concentration of Gr, but it is not stable and the efficiency of solar cell suffers heavy degradation. Here, we have developed a novel Gr-Si device structure with the coupling of two-dimensional Gr with zero-dimensional Pt nanoparticles on the top of bulk Si. The utilization of Pt nanoparticle can effectively enhance the sunlight absorption of solar cells by the plasmonic effect. Meanwhile, the carrier concentration and work function of Gr get greatly improved by physical doping of high-work-function Pt nanoparticle, and therefore the potential barrier at Gr-Si interface is significantly increased. More interestingly, the photo-induced doping of Pt nanoparticles for the Gr based on charge transfer has been observed for the devices under sunlight illumination. As a result, an efficiency of 7% has been achieved for our pristine solar cells, which is much higher than that of the control ones, ~4%. These devices with integration of zero-two-three dimensional materials have excellent air-stability, much more advantageous than the chemically doped ones. The efficiency of solar cell can further reach 10% by the application of spin-coated TiO2 anti-reflective film. These results point out a new route to the fabrication of high efficiency Gr-Si solar cells for photovoltaic application.

In this paper, we have investigated the effect of phosphorus diffusion gettering on the precipitated Cu in silicon via rapid thermal process (RTP). It is found that, for dot-like or star-like precipitates, the RTP-based phosphorus diffusion technique is efficient for gettering out the precipitated Cu. A two-step RTP gettering process is much more effective than a single-step RTP process. Furthermore, the choice of oxygen ambient can enhance the Cu gettering efficiency due to the involvement of considerable self-interstitial silicon atoms. The minority carrier lifetime of the sample subjected to RTP-based phosphorus gettering has also been verified to be significantly enhanced. These results are of interest for the gettering engineering of high-efficiency silicon solar cells.

Graphene/silicon (Gr/Si) solar cells have attracted interest for their potential in low-cost photovoltaic applications. Inserting a p-type organic hole transporting layer (HTL) in-between the Gr and Si would suppress carrier recombination and improve the performance of the solar cells. Here, we report highly stable and high-performance Gr/Si solar cells fabricated by using a room-temperature process. Spiro-OMeTAD was selected as the HTL for its novel electrical and optical properties. The employment of spiro-OMeTAD led to an impressive power conversion efficiency (PCE) of 13.02%. Moreover, our solar cells exhibit excellent stability with a PCE of ∼11% for over four months. These results could be encouraging for the development of Gr/Si solar cells toward practical applications. Meanwhile, this work offers a universal solution for the application of organics in Gr-based optoelectronics and photovoltaics from the viewpoint of device robustness.

Graphene-on-silicon (Gr–Si) heterojunction solar cells have recently attracted significant attention as promising candidates for low-cost photovoltaic applications. However, the power conversion efficiency of Gr–Si solar cells is generally smaller than 4% without chemical doping treatments. It is mainly limited by the low work function of Gr and high density defect states at the Gr–Si interface. Here, we have reported a new structure of Gr–Si solar cells by introducing a graphene oxide (GO) interlayer to engineer the Gr–Si interface for improving device performance. It is found that the GO interlayer can effectively increase open circuit voltage and meanwhile suppress the interface recombination of solar cells. As a result, a maximum efficiency of 6.18% can be achieved for the Gr/GO/Si solar cells, which is a new record for the pristine monolayer Gr–Si solar cell reported to date. Further, it is clarified that the Gr/GO/Si solar cell is significantly more stable than the Gr–Si solar cell with chemical doping. These results show a new route for fabricating efficient and stable chemical-doping-free Gr–Si solar cells.

Organic–inorganic lead halide perovskite solar cells (PSCs) with TiO2-based architectures have emerged for highly efficient photovoltaic conversion in recent years, while their serious light soaking instability limits their practical applications. Here, we have successfully introduced fullerene [6,6]-phenyl-C61-butyric acid 2-((2-(dimethylamino)ethyl)(methyl)-amino)-ethyl ester (PCBDAN) as an interfacial modifier for the TiO2 electron transport layer (ETL) in planar PSCs, which can significantly improve the photovoltaic conversion efficiency and light soaking stability of the devices. The quality of the perovskite film and electron extraction efficiency between the perovskite and ETL are both improved by introducing the PCBDAN interfacial layer. An improved power conversion efficiency (PCE) of 16.78% can be obtained for the device with PCBDAN under AM 1.5G illumination (100 mW cm−2). And the light soaking stability of the planar device is greatly improved after modification. This work provides a feasible way by interfacial modification for the realization of highly efficient devices without light-soaking degradation.

Graphene/silicon (Gr/Si) solar cells have attracted extensive research interest for their potentials in low-cost photovoltaic applications. However, the performance of Gr/Si solar cells is still limited by the working principles of Schottky junctions. This work developed a new type of Gr/Si solar cell with a self-generated quasi p–n junction. In such devices, a strong upward band bending is caused by considerable charge transfer from Si, resulting in a p-type layer being formed at the near-surface of the n-type Si substrate. They have similar rectification characteristics to conventional p–n junctions, and are even superior due to the absence of the “dead layer”. Here, a thermal evaporation deposited tungsten tri-oxide (WO3) interlayer was inserted between the Gr and Si to form the quasi p–n junction Gr/Si solar cells, achieving a high power conversion efficiency (PCE) of 10.59% for Gr/Si solar cells without chemical doping. The concept of a self-generated quasi p–n junction offers a possibility to overcome the limitations affecting the development of Gr/Si solar cells, and shows a promising future for diverse transition metal oxides for the fabrication of low-cost, high-efficiency and stable photovoltaic devices in the future.