Xu Pan

Performance enhancement of perovskite solar cells using a La-doped BaSnO3 electron transport layer

High efficiency organic–inorganic hybrid perovskite solar cells have experienced rapid development and attracted significant attention in recent years. Electron transport layers (ETLs) play an important role in extracting and transporting electrons in devices. To date, the most widely used ETL is still based on TiO2, whereas studies on other novel ETLs are not sufficient. A novel mesoporous ETL based on La-doped BaSnO3 (LBSO) has been investigated herein. The LBSO nanoparticles were synthesized under relatively mild conditions and proven to be a suitable material for mesoporous ETL. After optimization, mesoporous LBSO-based solar cells exhibited the best power conversion efficiency of 15.1%. By comparing mesoporous LBSO, BSO, and TiO2-based devices, the LBSO-based devices exhibit the highest Jsc, which can be attributed to the much higher electron mobility of LBSO. The electron transport and recombination were investigated by photoluminescence (PL) spectrum and transient absorption spectrum (TAS). The LBSO-based devices exhibit efficient electron transport and low recombination.

Ligand-free nano-grain Cu2SnS3 as a potential cathode alternative for both cobalt and iodine redox electrolyte dye-sensitized solar cells

Tetragonal phase Cu2SnS3 (CTS) in the form of nano-grain thin film serves as an efficient inexpensive electrocatalyst alternative to the commonly used Pt in dye-sensitized solar cells (DSSCs) exhibiting remarkable electrochemical stability and electrocatalytic activity for both cobalt (Co(III)/Co(II))- and iodine (I3−/I−)-based redox electrolytes. In this study, the catalytic activity of the CTS electrode was first theoretically predicted via first-principles calculations using density functional theory. Electrochemical measurements confirm their superior catalytic performance to Pt toward both the reduction of I3− and Co3+. Significantly, ensuing DSSCs with the CTS cathode demonstrate a photovoltaic efficiency of 10.26%, higher than that with Pt (9.31%). Through impedance spectra, we also show that increasing the amount of CTS loading can further enhance its apparent catalytic performance. However, improving the crystallization of the CTS film by increasing the annealing temperature to a certain degree will only reduce its activity.

Promoting perovskite crystal growth to achieve highly efficient and stable solar cells by introducing acetamide as an additive

To date, perovskite solar cells (PSCs) have achieved superior photovoltaic performance with a high power conversion efficiency (PCE) of over 22%. However, there are very few devices which have a high PCE and high stability simultaneously. In this study, we fabricated PSCs made from (FAPbI3)0.85(MAPbBr3)0.15 using the non-volatile Lewis base acetamide (CH3CONH2) as an additive. Compared to a reference device, the device containing 5xa0mg mL−1 CH3CONH2 displayed a markedly improved PCE of 19.01% and less hysteresis, due to its high-quality film with a better crystal structure, evidently larger grain size and greater thickness. In addition, the device with CH3CONH2 exhibited better humidity and heat stability. The unsealed device could maintain about 70% and 50% of its starting PCE under around 50% and 80% relative humidity (RH) for 1000 h and 700 h, respectively. Meanwhile, the unsealed device with CH3CONH2 could retain about 80% and 60% of its starting PCE at 60 °C and 85 °C for 200 h and 150 h, respectively. These results clearly show that using CH3CONH2 as an additive can promote crystal growth and enhance the grain size of perovskite thin films and introducing a suitable additive can realize the simultaneous improvement of the PCE and stability of PSCs.

Adjusting the Introduction of Cations for Highly Efficient and Stable Perovskite Solar Cells Based on (FAPbI3)0.9(FAPbBr3)0.1

Although the power conversion efficiency (PCE) of perovskite solar cells (PSCs) has increased to 22.7u2009%, the instability when exposed to moisture and heat has hindered their further practical development. In this study, to gain highly efficient and stable perovskite components, methylammonium (MA), Cs, and Rb cations are introduced into a (FAPbI3 )0.9 (FAPbBr3 )0.1 (FA=formamidine) film, which is rarely used because of its poor photovoltaic performance. The effects of different contents of MA, Cs, or Rb cations on the performance of (FAPbI3 )0.9 (FAPbBr3 )0.1 films and devices are systematically studied. The results show that the devices with Cs cations exhibit markedly improved photovoltaic performance and stability, attributed to the clearly enhanced quality of films and their intrinsic stability. The (FAPbI3 )0.9 (FAPbBr3 )0.1 devices with 10u2009% Cs show a PCE as high as 19.94u2009%. More importantly, the unsealed devices retain about 80u2009% and 90u2009% of the initial PCE at 85u2009°C after 260u2005h and under 45±5u2009% relative humidity (RH) after 1440u2005h, respectively, which are better than that with 15u2009% MA and 5u2009% Rb under the same conditions. This indicates that a highly efficient and stable perovskite component has been achieved, and PSCs based on this component are expected to promote their further development.

New-type highly stable 2D/3D perovskite materials: the effect of introducing ammonium cation on performance of perovskite solar cells

Perovskite solar cells (PSCs) have drawn wide attention due to the rapidly rising efficiency which presently attains over 23%. However, problems of instability continue to plague the high-efficiency devices impairing their practical applications. Here, by firstly introducing smaller-size NH4+ into (FAPbI3)0.85(MAPbBr3)0.15 (FA/MA) to form a novel 2D- 3D mixed structure, we designed and prepared new-type hybrid perovskite materials of [(NH4)2.4(FA)n−1PbnI3n+1.4]0.85 (MAPbBr3)0.15 (n=3, 5, 7, 9 and 11) (A/FA/MA) and used them as absorber in solar cells. Especially, unlike the reported 2D/MD perovskite perovskites based on larger-size ammonium salts; A/FA/MA perovskites are the first to display red-shift light absorption and decreased band gaps in comparison to normal perovskites. Consequently, when n=9, the A/FA/MA device shows outstanding performance with a solar to electric power conversion efficiency (PCE) of 18.25% and negligible hysteresis. When the encapsulated A/FA/MA perovskite device was soaked in full sunlight for 1,000 h, the PCE remains almost unchanged. Moreover, the unsealed A/FA/MA PSCs maintain 90% of their initial PCE when aged at high humidity conditions over the same 1000-h time period. Our findings provide a guide for the future development of such novel perovskites and it is helpful to select more suitable ammonium salt to obtain highly efficient and stable 2D-3D PSCs.摘要钙钛矿太阳电池因其快速增长的效率而引起了广泛关注, 但不稳定性极大的影响了它的实际应用. 这里, 我们首次将小尺寸的NH4+引入三维钙钛矿中, 制备了新型的二维/三维混合钙钛矿材料. 特别地, 与文献报道的二维钙钛矿不同的是, 新型的二维/三维混合钙钛矿是首个显示光学性能红移和带隙减少的. 当n=9时, 电池显示出优越的光伏性能, 效率达到了18.25%, 且具有可忽略的迟滞. 封装的电池在 标准的AM 1.5G光照下放置1000小时后, 效率没有明显降低. 在高湿度条件下老化1000小时, 未封装的电池保持了90%的初始效率. 这些发现为发展新型钙钛矿材料提供了指导, 有助于获得高效稳定的二维钙钛矿太阳电池.

Application of facile solution-processed ternary sulfide Ag 8 SnS 6 as light absorber in thin film solar cells

Light absorber is critical to the further applications of thin film solar cells. Here, we report a facile solution-processed method with an annealing temperature below 250°C to fabricate Ag8SnS6 (ATS) light absorber for thin film solar cells. After optimization, the ATS-based thin film solar cells exhibited a reproducible power conversion efficiency (PCE) of about 0.25% and an outstanding long-term stability with 90% of the initial PCE retained after a more than 1,000 h degradation test. This research revealed the potential application of ATS as an earth-abundant, low toxic and chemically stable light absorber in thin film solar cells.摘要吸光材料是薄膜太阳电池进一步应用的重要因素. 三元硫化物Ag8SnS6 (ATS)拥有诸多优秀的光电性质. 然而, 关于ATS在吸光材料方面的应用鲜有报道. 因此, 本文通过使用一种退火温度低于250°C的温和溶液法制备ATS吸光材料并将其应用于薄膜太阳电池之中. 在优化之后, 基于ATS的薄膜太阳电池展现出了具有潜力的光伏性能以及可再现的0.25%光电转化效率. 更重要的是, 基于ATS的器件展现出了卓越的长期稳定性, 在超过1000小时的老化测试后器件仍然还有90%的初始效率. 本研究不仅揭示了含量丰富、 低毒且化学性质稳定的ATS作为吸光材料的潜力, 也为薄膜太阳电池中新型吸光材料的研究提供了全新的视角.

Efficient Solar Cells with Enhanced Humidity and Heat Stability Based on Benzylammonium-caesium-formamidinium Mixed-Dimensional Perovskites

Perovskite solar cells (PSCs) exhibit remarkable photovoltaic performance with a power conversion efficiency (PCE) over 22%, but they exhibit instability in moist environments and at high temperatures. Compared to 3D perovskites, two-dimensional (2D) layered perovskites display excellent environmental stability but relatively poor photovoltaic performance. Here, we combined 2D/3D perovskites and simultaneously introduced the cesium cation (Cs+) to fabricate benzylammonium–caesium–formamidinium mixed-dimensional (MD) perovskite (BE/FA/Cs MD perovskite) solar cells. The BE/FA/Cs MD perovskite device with an optimal benzylammonium content exhibits a PCE as high as 19.24%. The improved PCE of 19.24% (BE/FA/Cs MD, x = 0.05) is attributed to great crystal orientation, outstanding surface quality, superior optical properties and enhanced charge transfer. More importantly, the BE/FA/Cs MD perovskite devices display superior humidity and heat stability. When subjected to 50% relative humidity (RH) for 1600 h and 85 °C for 240 h in the dark, the BE/FA/Cs MD (x = 0.05) devices without encapsulation retain 85% and 83% of their initial PCE, respectively. These results provide us with an important method to obtain highly efficient MD PSCs with long-term stability as a next-generation photovoltaic energy source.

High-Performance Mixed-Dimensional Perovskite Solar Cells with Enhanced Stability against Humidity, Heat and UV Light

Despite three-dimensional (3D) perovskite solar cells (PSCs) having a high power conversion efficiency (PCE) beyond 22%, they are unstable under humidity, oxygen and ultraviolet light. Two-dimensional (2D) perovskites exhibit high stability but have poor photovoltaic performance. To simultaneously enhance the PCE and stability of PSCs, we designed new mixed-dimensional (MD) PSCs by introducing HOCH2CH2NH3I (EAI) into (FAPbI3)0.85(MAPbBr3)0.15 3D perovskite. The MD devices made with [(EA)2PbI4]x[(FAPbI3)0.85(MAPbBr3)0.15]1−x exhibit outstanding photovoltaic performance with an improved PCE of 18.79% due to the outstanding crystal structure, superior surface morphology, enhanced charge transport and reduced carrier recombination. More importantly, the MD devices display markedly improved stability against humidity, heat and UV light. After exposing to about 50% relative humidity (RH) for over 1700 hours (h), the unsealed devices retain about 85% of the initial PCE. After exposing to air at 85 °C for 220 h and exposing to continuous UV irradiation for 13 h, all the unsealed devices retain PCEs of about 60% of the initial value. These results demonstrate that designing a novel MD perovskite is a significant strategy for improving both photovoltaic performance and stability of PSCs.

An ultrathin SiO2 blocking layer to suppress interfacial recombination for efficient Sb2S3-sensitized solar cells

Interfacial charge recombination is a serious problem in semiconductor-sensitized solar cells which severely limits the power conversion efficiency. Herein, an ultrathin SiO2 blocking layer was introduced to the TiO2 surface to suppress the interfacial recombination in Sb2S3-sensitized solar cells. The SiO2 blocking layer was deposited by a simple chemical bath method. Due to the unique features of the SiO2 layer, the Sb2S3 sensitizer shows a remarkable change in the morphology after SiO2 coating, forming numerous irregular large crystals which did not bring a negative impact. Electrochemical impedance spectra and open-circuit voltage-decay analysis confirm that the SiO2 layer efficiently suppresses the interfacial recombination at the TiO2/Sb2S3 interface which is the major recombination path in the solar cells. As a result, the device exhibits remarkably enhanced open-circuit voltage, fill factor and power conversion efficiency.

Acquiring High-Performance and Stable Mixed-Dimensional Perovskite Solar Cells by Using a Transition-Metal-Substituted Pb Precursor

In recent years, as the most promising photovoltaic technology, lead halide perovskite solar cells (PSCs) have become a research hotspot owing to their super-high power conversion efficiency (PCE) and simple preparation method. However, the toxicity of lead and instability under high humidity and temperature greatly affects their further development. In this study, we investigated three kinds of non-toxic transition metal cations (Zn2+ , Mn2+ , and Ni2+ ) at 3u2009% to partially substitute lead cations and form mixed-dimensional (MD) perovskites. Among these transition metals, Zn2+ is the most suitable to replace Pb2+ and Zn-MD perovskite device exhibits the best PCE of 18.35u2009%. In addition, we further studied the humidity and heat stability of methylammonium lead iodide (MA), Zn-MD, Mn-MD, and Ni-MD perovskite devices. Upon exposure to about 50u2009% relativity humidity (RH) for 800u2005h, the MA and three MD devices, respectively, maintain 30u2009%, 81u2009%, 80u2009%, and 74u2009% of their original PCE. After aging at 60u2009°C for 100u2005h, the PCEs of the four PSCs retain 40u2009%, 84u2009%, 85u2009%, and 76u2009% of their starting values, respectively. The results show that the three MD perovskite devices have high humidity and heat stability and using transition-metal-substituted Pb can gain long-term stability and reduced toxicity of PSCs.