钙钛矿太阳能电池中D-A-D型空穴传输材料的研究进展

钙钛矿太阳能电池(Perovskite Solar Cells, PSCs)作为一种新型太阳能电池,由于其短时间内快速提升的光电转换效率而获得了全世界范围内的广泛关注。空穴传输材料(Hole Transporting Materials, HTM)是钙钛矿太阳能电池的重要组成部分,因此,设计开发经济、高效、稳定的HTM对PSCs的发展具有重要意义。本文综述了2009年以来线型给体-受体-给体(Donor-Acceptor-Donor, D-A-D)结构有机小分子空穴传输材料在PSCs中的应用,详细介绍了各空穴传输材料分子结构对PSCs的光电转换效率和器件稳定性等性能的影响。在此基础上,对未来线型D-A-D型空穴传输材料的发展进行了展望。     

富勒烯材料在钙钛矿太阳能电池中的应用

有机无机杂化钙钛矿太阳能电池自2009年出现以来，经过短短十余年的发展，光电转化效率已提升到24%以上，引起了广泛的关注。富勒烯材料具有较高电子迁移率、可调控的能级以及可低温成膜等特性，在钙钛矿太阳能电池中可以用于电子传输层、钙钛矿层添加剂、界面修饰层，甚至还能够在空穴传输层中发挥作用。这些应用不仅提高了电池的光电转化效率和稳定性，还能有效降低电池的磁滞效应。本综述就富勒烯材料在钙钛矿太阳能电池各组成部分的应用进行了详细的介绍，并总结了通过修饰富勒烯分子结构提高电池性能的基本规律，这些结果对推动富勒烯材料在钙钛矿太阳能电池领域的应用有重要意义。     

Enhanced power conversion efficiency of perovskite solar cells using dopant-free carbon nanotubes-Spiro-OMeTAD

Paintable carbon-based perovskite solar cells (PSCs) are of tremendous attention due to their structural stability and low fabrication cost. However, the poor interfacial contact and unsatisfied energy band alignment between carbon and perovskite lead to relatively low efficiency of carbon-based perovskite solar cells. Herein, we employed a multi-functional holes transfer layer, a dopant-free Spiro-OMeTAD composited with CNTs (CNTs-spiro), to bridge the interface between carbon and perovskite and optimize the energy band alignment in carbon-based PSCs. The power conversion efficiency of the PSCs with the CNTs-spiro layer (10.45%) has an enhancement of 17.51% compared with the PSC without the CNTs-spiro layer (8.62%). Our non-encapsulated devices showed excellent stability under light, air, or ambient conditions. The CNTs-spiro composition may be a promising hole transfer material for PSCs with high efficiency and high stability.     

The optimum titanium precursor of fabricating TiO<Subscript>2</Subscript> compact layer for perovskite solar cells

Perovskite solar cells (PSCs) have attracted tremendous attentions due to its high performance and rapid efficiency promotion. Compact layer plays a crucial role in transferring electrons and blocking charge recombination between the perovskite layer and fluorine-doped tin oxide (FTO) in PSCs. In this study, compact TiO₂ layers were synthesized by spin-coating method with three different titanium precursors, titanium diisopropoxide bis (acetylacetonate) (c-TTDB), titanium isopropoxide (c-TTIP), and tetrabutyl titanate (c-TBOT), respectively. Compared with the PSCs based on the widely used c-TTDB and c-TTIP, the device based on c-TBOT has significantly enhanced performance, including open-circuit voltage, short-circuit current density, fill factor, and hysteresis. The significant enhancement is ascribed to its excellent morphology, high conductivity and optical properties, fast charge transfer, and large recombination resistance. Thus, a power conversion efficiency (PCE) of 17.03% has been achieved for the solar cells based on c-TBOT.     

钙钛矿太阳能电池研究进展

钙钛矿太阳能电池(PSCs)近几年迅速发展,截至目前,其能量转换效率已经超过23%,这可能使光伏产业发生革命性的变化。基于最新的研究进展,介绍了钙钛矿太阳能电池的结构和工作机理,简要综述了空穴传输材料(HTM)在钙钛矿太阳能电池中的应用。最后,指出了钙钛矿太阳能电池目前存在的一些问题及未来的研究方向。     

Spray-coated SnO2 electron transport layer with high uniformity for planar perovskite solar cells

SnO₂ has been proven to be an effective electron transport layer(ETL)material for perovskite solar cells(PSCs)owing to its excellent electrical and optical properties.Here,we introduce a viable spray coating method for the preparation of SnO2 films.Then,we employ a SnO₂ film prepared using the spray coating method as an ETL for PSCs.The PSC based on the spray-coated SnO₂ ETL achieves a power conversion efficiency of 17.78%,which is comparable to that of PSCs based on conventional spin-coated SnO₂ films.The large-area SnO₂ films prepared by spray coating exhibit good repeatability for device performance.This study shows that SnO₂ films prepared by spray coating can be applied as ETLs for stable and high-efficiency PSCs.Because the proposed method involves low material consumption,it enables the low-cost and large-scale production of PSCs.     

Research progress on stability enhancement of CsPbX3 perovskite and photovoltaic devices

The CsPbX₃ (X is halide anions) based all-inorganic perovskites are regarded to be one of the most appealing research hotspots among perovskite photovoltaics in the past few years, mainly due to their superior thermal stability compared to the organic-inorganic hybrid counterparts. At present, the highest photoelectric conversion efficiency of all-inorganic perovskite solar cells has reached 19.03%, which has good development potential. However, the Goldschmidt tolerance factor of this type of perovskite is close to the critical boundary value, which leads to phase instability. Accordingly, numerous works have been published on the stability enhancement of CsPbX₃ perovskite in recent years. This review summarizes the progress and strategies in the preparation of stable and efficient all-inorganic perovskite solar cells (PSCs), including the enlargement of tolerance factor, enhancement of activation energy barrier for phase transition (black phase to yellow phase), and decreasing the surface energy as well as modulation of the crystallization procedure. Finally, challenges and perspective of the future development of all-inorganic CsPbX₃ based PSCs are presented.     

CsPbX3钙钛矿材料与光伏器件稳定性强化研究进展

基于CsPbX₃(X为卤素阴离子)的全无机钙钛矿与含甲胺、甲脒等有机阳离子的有机-无机杂化钙钛矿相比，具有更优异的热稳定性，是近几年来钙钛矿光电领域最具吸引力的研究热点之一。目前全无机钙钛矿太阳电池的最高光电转换效率已经达到19.03%，具有很好的发展潜力。然而，这类钙钛矿材料的Goldschmidt容忍因子接近临界值，存在相不稳定的问题。近年来已经有相当多的研究聚焦于CsPbX₃钙钛矿材料与器件的稳定性强化工作。从增大容忍因子、提高相转变能垒、减小表面能、调控结晶过程等策略与方法入手，系统总结了近年来在制备稳定高效全无机CsPbX₃钙钛矿太阳能电池方面的进展，并对面临的挑战和未来的发展方向做出了展望。     

A thioacetamide interlayer anchoring TiO2 and (FAPbI3)1−x(MAPbBr3)x for high-performance perovskite solar cells

In the perovskite solar cells (PSCs), traps of the perovskite film or interface are the research focus, which can severely hinder charge transfer and benefit charge recombination, thus weakening the photoelectric performance of the devices. Herein, a Thioacetamide (TAA) interfacial layer is used to passivate the traps of PSCs. Comparing to the control device (17.65%), the TAA-based solar cells can achieve an enhanced efficiency of 19.14%. It is found that the passivation caused by TAA occurs through the interactions of sulfur in TAA with undersaturated Pb in perovskite and Ti⁴⁺ in TiO₂, resulting in a faster and more efficient charge transfer and a greatly reduced trap density from 3.36 × 10¹⁶ cm⁻³ to 1.93 × 10¹⁶ cm⁻³. It is shown that the modification method using TAA may be helpful for passivating traps and obtaining excellent photoelectric properties of PSCs.     

Recent Progress of Innovative Perovskite Hybrid Solar Cells

Recently, innovative perovskite hybrid solar cells have attracted great interest in solar cell research fields, such as dye-sensitized solar cells, organic photovoltaics, thin-film solar cells, and silicon solar cells, because their device efficiencies are gradually approaching those of crystalline Si solar cells, and they can be fabricated by cheap low-temperature solution processes. Here, we review the recent progress of innovative perovskite hybrid solar cells. The introduction includes the general concerns about solar cells and why we need innovative solar cells. The second part explains the structure and the material properties of hybrid perovskite materials. We focus on why the hybrid perovskite materials can exhibit excellent solar cell properties, such as high open-circuit voltage. The third part introduces recent progress in innovative perovskite hybrid solar cells, in terms of device architecture and deposition methods for dense perovskite thin films with full surface coverage. The device architecture is important in attaining high power conversion efficiency; the device operating mechanism is dependent on the device structure; and the pinhole-free dense perovskite thin films with full surface coverage are crucial for achieving high efficiency. Finally, we summarize the recent progress in perovskite hybrid solar cells, and the issues to be solved, in the summary and outlook section.     

Cu2ZnSnS4 as a hole-transport layer in triple-cation perovskite solar cells: Current density versus layer thickness

Cu₂ZnSnS₄ (CZTS) is a good candidate for cost-effective perovskite solar cells (PSCs) due to its direct bandgap with a value of 1.4–1.5 eV. In this study, we investigate CZTS ink as an inorganic hole-transport-layer (HTL) in CsMAFAPbIBr mixed halide PSCs. We study the cell efficiency and hole extraction from the perovskite layer for different thicknesses of HTL. The optimized device exhibits better hole selectivity, and the best efficiency of the device (12.84%) is achieved for the CZTS layer with a thickness of 159 nm. The prepared samples were also tested by open-circuit voltage decay analysis and electrochemical impedance spectroscopies. Results show that the optimized device effectively prohibits the electrons-holes recombination with a charge transfer resistance of 9.38 Ω cm². This work suggests that the optimal thickness of CZTS as an HTL in triple-cation PSC is about 159 nm by giving short-circuit current density of 23.69 mA cm^?2.     

Using water‐soluble nickel acetate as hole collection layer for stable polymer solar cells

We report polymer solar cells (PSCs) based on poly(3‐hexylthiophene (P3HT) and [6,6]‐phenyl‐C₆₁‐butyric acid methyl ester (PCBM) using water‐soluble nickel acetate (Ni(CH₃COO)₂, NiAc) instead of acidic poly(3,4‐ethylenedioxythiophene) : poly(styrenesulfonate) (PEDOT : PSS) as hole collection layer (HCL) between the indium tin oxide (ITO) electrode and photoactive layer. The NiAc layer can effectively decrease R_s and increase R_p and shows effective hole collection property. Under the illumination of AM1.5G, 100 mW/cm², the short‐circuit current density (J_sc) of the NiAc based device (ITO/NiAc/P3HT : PCBM/Ca/Al) reach 11.36 mA/cm², which is increased by 11% in comparison with that (10.19 mA/cm²) of PEDOT : PSS based device (ITO/PEDOT : PSS/P3HT : PCBM/Ca/Al). The power conversion efficiency of the NiAc based devices reach 3.76%, which is comparable to that (3.77%) of the device with PEDOT : PSS HCL under the same experimental conditions. Moreover, NiAc based PSCs show superior long‐term stability than PEDOT : PSS based PSCs. Our work gives a new option for HCL selection in designing more stable PSCs. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

有机-无机杂化钙钛矿太阳能电池的研究进展

有机-无机杂化钙钛矿材料不仅具有较高的光吸收能力和载流子迁移率,同时具有双极性特征以及合成方法简单等优点,目前已成为最有发展前途的太阳能电池材料,其光电转化效率在7年内从3.8%迅速提升到20%以上,并有进一步提高的空间。简单介绍了钙钛矿材料的结构与性质,综述了钙钛矿太阳能电池的研究进展,指出了目前电池发展中亟需解决的问题及未来的发展方向。     

Sulfides as a new class of stable cost-effective materials compared to organic/inorganic hole transport materials for perovskite solar cells

Perovskite solar cells (PSCs) have received a remarkable attention compared to the other types of solar cells due to their high carrier mobility, low recombination rate, and rapid increase in terms of efficiency in short time. However, two essential parameters being stability and cost are still challenging with these kinds of solar cells. Hole transport materials (HTMs) play an important role in PSCs as they can be effective in the charge transportation, determining the device stability and having a large share of cell costs, and overall resulting in the enhancement of open-circuit voltage (V_oc), short-circuit current (J_sc), and fill factor (FF). In addition to the organic HTMs which are widely used in PSCs, various inorganic HTMs mainly divided into the oxide and sulfide subgroups, have been developed in order to improve both stability and cost of PSCs. Herein, we provide an overview of the diverse types of HTMs, from organic to inorganic, especially oxide and sulfide inorganic HTMs and investigate the physical properties, synthesis, and their applications in various PSCs for both mesoporous and planar structure in the hope of encouraging further research and the optimization of these materials.     

Air fabrication of SnO2 based planar perovskite solar cells with an efficiency approaching 20%: Synergistic passivation of multi-defects by choline chloride

Defects in the perovskite films impose a serious issue on the PCE and stability of the SnO₂ based planar perovskite solar cells (SP–PSCs). So far, most researches have focused on regulating the SnO₂/perovskite interface to improve performance. However, defect passivation of the perovskite/HTM interface is more significant and potential. Herein, the non-toxic and cheap choline chloride was performed to passivate multiple defects of the MAPbI₃/HTM interface in ambient atmosphere. An optimal PCE of 19.93% (the average PCE was 18.60%) was obtained for the passivated device. Furthermore, the effect and mechanism of choline chloride on the humid and thermal stability of the SP-PSCs was investigated in detail. The passivated device without encapsulation retained 91% of its initial efficiency after 20 days in humid environment (20 ± 5 °C, 55 ± 5% RH) and 95% of the initial value under heating for 7 cycles (85 °C). Chloride ions with smaller radius and larger electronegativity formed stronger ionic bonding with Pb²⁺ to passivate I^? vacancy defects, while choline ions passivated MA⁺ vacancies. This work not only provides guidance for fabrication of an efficient and stable device in air, but also opens an avenue to understanding of relation between stability and defects in the SP-PSCs.     

Perovskite Solar Cells Fabricated by Using an Environmental Friendly Aprotic Polar Additive of 1,3-Dimethyl-2-imidazolidinone

Perovskite solar cells (PSCs) have great potentials in photovoltaics due to their high power conversion efficiency and low processing cost. PSCs are usually fabricated from PbI₂/dimethylformamide solution with some toxic additives, such as N-methyl pyrrolidone and hexamethylphosphoramide. Here, we use an environmental friendly aprotic polar solvent, 1,3-dimethyl-2-imidazolidinone (DMI), to fabricate perovskite films. By adding 10 vol% DMI in the precursor solution, high-quality perovskite films with smooth surface are obtained. By increasing annealing temperature from 100 to 130 °C, the average grain size of the perovskite increases from ~?216 to 375 nm. As a result, the efficiency of the PSCs increases from 10.72 to 14.54%.     

溶液法制备有机-无机杂化钙钛矿薄膜的研究进展

有机-无机杂化钙钛矿（简称钙钛矿）太阳能电池在近年取得了重大突破,实验室小面积器件的光电转换效率从最初2009年的3.8%提升至现今的22.1%。本文从钙钛矿材料的物化性能、钙钛矿太阳能电池的结构、钙钛矿薄膜的制备方法等方面全面分析了钙钛矿太阳能电池的优势和不足。首先简要回顾了钙钛矿太阳能电池问世以来几个重要发展历程和主流电池器件结构的演变,着重讨论了吸光层钙钛矿薄膜的制备方法,包括一步溶液法、分步旋涂-浸渍法、两步旋涂法、气相沉积法,分析了影响钙钛矿成膜的关键因素、微观形貌控制的工艺技术,对溶剂的选择、溶质成分的调控（包括铅源、各类添加剂的选择）以及钙钛矿结晶的粗化做了详细探讨。指出今后的工作重点在于如何精确控制钙钛矿薄膜的化学成分,提高可重复性和良品率;加强器件工作机理、成膜机理的研究;着眼于大面积器件的制备;提高器件的稳定性及开发环境友好型无铅或少铅电池。     

Lead free CsSn0.5Ge0.5I3 perovskite solar cell with different layer properties via SCAPS-1D simulation

Organic–inorganic halide perovskite solar cells (PSCs) have been extensively studied due to their simple fabrication methods and obvious device efficiency advantages. In this work, the perovskite CsSn_0.5Ge_0.5I₃ is used as the light absorption layer, which is doped with Ge²⁺ in CsSnI₃ to improve its stability. The polymers of 3-hexylthiophene (P3HT) with excellent optoelectronic properties and low price, and SnO₂ with high electron extraction ability is selected as charge transport layers. Based on these, a novel PSC structure (FTO/SnO₂/IDL1/CsSn_0.5Ge_0.5I₃/IDL2/P3HT/Au) has been simulated via solar cell capacitor simulator (SCAPS-1D). The PSC performance is optimized by adjusting a series of parameters, including the layer thickness, defect density, electron affinity potential energy, and operating temperature, and so forth. The results show that the PSC defects are passivated by adjusting the appropriate parameters, and the final optimized open circuit voltage (V_OC) is 1.08 V, short-circuit current density (J_SC) is 27.37 mA/cm², fill factor (FF) is 83.32%, while the power conversion efficiency (PCE) is increased from the initial 10.89% to 24.63%, which provides theoretical reference for experiments and new ideas for the preparation and development of efficient and environmentally friendly PSCs. Finally, the effect of different metal cathodes with and without hole transport layer (HTL) on PSC performance is compared. The PSCs without HTL are more dependent on battery cathodes, which provided a way to replace precious metals with other electrode materials.     

Surface modification of electron transport layers based on TiO2 nanorod boosts efficiency of perovskite solar cells

In this work, TiO₂ heterostructure thin films including rutile TiO₂ nanorods (TNRs) and anatase TiO₂ nanoparticles (TNPs) on fluorine-doped tin oxide (FTO) glass are fabricated by the hydrothermal method and are applied as electron transport layers (ETLs) in MAPbI₃-based perovskite solar cells (PSCs). To enhance the surface area of ETL, TNRs are first etched in acidic solution by another hydrothermal process for different reaction times before coating with TNPs. The morphological and structural properties of TNRs after etching are carefully investigated. Interestingly, the surface modification of TNR thin film by appropriate TNP deposition and etching improves significantly the efficiency of PSC devices by more than 1.6 times. To further improve the performance of PSC, phenyl-C61-butyric acid methyl ester (PCBM) is used to enhance the charge transfer efficiency at the ETL/perovskite interface, and the optimal PSC device shows the champion efficiency of 18.50% with low charge transfer resistance (11.56 ohms).     

Dioctylfluorene‐thiophene based conjugated copolymers for bulk heterojunction solar cells and enhanced power conversion efficiency via methanol treatment

Sensible design and synthesis of conjugating polymers is important to the development of polymer solar cells (PSCs). In this work, we synthesized and characterized two dioctylfluorene‐thiophene based conjugated copolymers, PFTDPP and PFTpBT, having different acceptor groups on the backbone. The photovoltaic properties of the copolymers blended with 6,6‐phenyl‐C₆₁‐butyric acid methyl ester (PC₆₁BM) as an electron acceptor were obtained. The PSC based on a conventional device configuration ITO/PEDOT:PSS/ Polymer:PC₆₁BM/LiF/Al showed power conversion efficiencies (PCEs) of 2.42% and 3.02% for PFTDPP and PFTpBT, respectively. Methanol treatment was introduced to further optimize device performance, and the solvent treatment gave a dramatic increase in PCE. The best PCEs could reach 4.25% and 4.20% after methanol treatment under AM 1.5G illumination with an intensity of 100 mW cm^?2 from a solar simulator. © 2015 Society of Chemical Industry