空穴传输材料在高效钙钛矿太阳能电池中的发展演变

钙钛矿太阳能电池(PSCs)转换效率已从2009年的3.8%上升到2017年的22.7%,其快速的发展可能使光伏工业进入革命新阶段。空穴传输材料(HTM)是构成高效钙钛矿太阳能电池的重要组成部分,开发和设计导电性好、成本低、稳定性好的空穴传输层材料对钙钛矿太阳能电池的研究显得非常重要。本文将近几年应用于钙钛矿太阳能电池中较高效的空穴传输材料归纳为有机小分子类、有机聚合物类和无机材料类,同时也介绍了无空穴传输层的钙钛矿电池。详细评述了基于各类空穴传输材料的钙钛矿太阳能电池的光电性能及稳定性,重点讨论了HOMO能级、空穴迁移率、添加剂的掺杂等因素对钙钛矿太阳能电池的影响。最后指出了空穴传输材料未来的研究重点和发展趋势。     

钙钛矿太阳能电池的研究进展

作为一种新型清洁可再生能源,钙钛矿太阳能电池(Perovskite solar cells,PSC)从发展至今已取得了重大的突破,成为研究的热点。主要介绍了钙钛矿太阳能电池的基本结构和工作原理及电子传输层、钙钛矿层、空穴传输层的制备方法,以及在发展过程中所面临的技术问题,最后展望了钙钛矿太阳能电池未来的研究重点及发展前景。     

钙钛矿太阳能电池空穴传输材料的研究进展

钙钛矿太阳能电池具有工艺简单、可弯曲、应用前景广阔等优点。从2009年出现起,至今其效率从3.8%提高到了22%以上,引起了研究者的广泛关注。介绍了钙钛矿太阳能电池的基本结构和工作原理,概述了钙钛矿太阳能电池空穴传输材料的研究进展,着重介绍了无机空穴传输材料的研究进展。最后展望了钙钛矿太阳能电池未来的发展与商业化应用。     

富勒烯在新型太阳能电池中的应用

新型太阳能电池包括有机太阳能电池、钙钛矿太阳能电池和量子点太阳能电池等,是一类十分有前景的光伏器件,目前有机太阳能电池和钙钛矿太阳能电池的能量转换效率分别超过了19%和25.6%。富勒烯材料具有较高的电子迁移率和良好的电子特性,被广泛应用于有机太阳能电池活性层、界面层,钙钛矿太阳能电池活性层和中间层等。在有机太阳能电池中,富勒烯材料作为活性层受体,可以提高器件电子传输能力;作为界面修饰层,可以有效降低接触电阻,抑制载流子的复合。在钙钛矿太阳能电池中,富勒烯材料作为活性层添加剂能钝化钙钛矿缺陷,抑制迟滞效应;作为中间层能优化界面形貌,促进电荷的提取与输运。本文综述了富勒烯材料在各个组成部分中的研究进展,并展望了富勒烯材料在各个组成部分中的发展前景,在此基础上,提出了未来的研究方向。     

低温TiO2/SnO2双电子传输层的光电性能及其在钙钛矿电池中的应用

作为有机-无机钙钛矿杂化太阳能电池(PSCs)常用的电子传输层(ETL),氧化钛(TiO2)须在高温下烧结才能结晶,因而难以适用于柔性和串联叠层太阳能电池.本文介绍了一种低温溶液法制备TiO2/氧化锡(SnO2)电子传输层,并通过对TiO2/SnO2ETL的系统光学和电学性能测试,证明TiO2/SnO2ETL与钙钛矿层...     

高效率双结钙钛矿叠层太阳能电池研究进展

以钙钛矿电池为顶电池的叠层太阳电池发展迅速,成为太阳能光伏领域的研究热点之一。随着电池结构和制备工艺的优化,叠层电池的光电转换效率快速提升,单片钙钛矿/晶硅叠层电池的效率已达到31.3%。本综述对近年来以宽带隙钙钛矿电池作为顶子电池、晶体硅电池及其他新型中窄带隙电池(钙钛矿电池、有机电池、铜铟镓硒(CIGS)电池)作为底子电池的叠层电池的研究进展进行了系统梳理,总结了叠层电池的顶电池、中间互联层和底电池的材料、结构及光电性能等方面的关键技术及难点,希望能够为进一步提升叠层电池效率提供一些思路。并对未来低成本高效叠层太阳能电池的光学和电学优化需求做出了分析与展望。     

碳材料在钙钛矿太阳能电池中的应用

钙钛矿太阳能电池具有材料成本低廉、生产工艺简单、光电转换效率高等优点,发展前景十分光明。碳材料因其价格低廉、高导电性、疏水性和化学稳定性等特点,被应用在钙钛矿太阳能电池的各个组成部分,用于提高电池性能和降低成本。本文根据应用在钙钛矿太阳能电池中的碳材料的维数进行分类,分别介绍了零维的C60、碳量子点和石墨烯量子点,一维的碳纳米管,二维的石墨烯及其衍生物、石墨炔和三维的石墨等在钙钛矿太阳能电池中的应用,对于将来实现钙钛矿太阳能电池的低成本商业化和大规模制造具有重要意义。     

以ZnO纳米棒阵列为电子传输层的无空穴层有机-无机杂化钙钛矿太阳能电池

近年来,有机-无机杂化钙钛矿太阳能电池(PSCs)发展迅速,其光电转化效率(PCE)已提升至23.3%,成为当今太阳能电池领域无可争议的研究焦点。研究发现,PSCs结构组成与性质对光电性能影响显著。其中,电子传输层的形貌结构不仅影响钙钛矿晶体的成长,同时也决定了电子扩散系数和电子寿命。本工作将ZnO纳米棒阵列(Nanorods array,NRAs)作为电子传输层,应用于无空穴传输层的基于碳对电极的杂化钙钛矿太阳能电池中。通过水热法制备了不同长度的ZnO NRAs,经测试发现,对应的钙钛矿电池的PCE随ZnO NRAs长度的增加呈先升高后下降的趋势,当ZnO NRAs长度为454 nm时,PCE最优为6.18%。     

有机电子传输材料在反式钙钛矿太阳能电池中的研究现状

近年来,反式结构的钙钛矿太阳能电池凭借制备工艺简单、可低温成膜、迟滞效应低、适合与传统太阳能电池结合制备叠层器件等优点,受到了人们广泛的关注,经过几年的发展,反式钙钛矿太阳能电池的光电转化效率已从3.9%提升到25.37%。其中电子传输层作为钙钛矿太阳能电池的重要组成部分,在提取和运输载流子、阻挡空穴、调节界面能级结构和抑制电荷复合等方面起着关键性的作用。一些有机材料(富勒烯及其衍生物、苝二酰亚胺、萘二酰亚胺等)凭借容易合成和纯化、能级可调、电子迁移率高、溶解性好、化学/热稳定性良好等优势,已经广泛应用于反式钙钛矿太阳能电池。本文主要介绍了不同有机电子传输材料在反式钙钛矿太阳能电池中的研究现状,还介绍了电子传输层掺杂和界面修饰两种提升器件性能的改性手段,旨在为开发全新的有机电子传输材料提供基础性的理论指导。     

基于氧化石墨烯空穴传输层的平面异质结钙钛矿太阳能电池

钙钛矿太阳能电池中传统空穴传输层Spiro-OMeTAD存在昂贵、易污染环境且制备困难等缺点,本工作采用氧化石墨烯(Graphene oxide,GO)作为空穴传输层,研究了不同浓度GO溶液制备的衬底对器件光电性能的影响.首先,采用旋涂法制备了GO薄膜,通过对分散液浓度的控制获得了不同厚度的GO衬底.其次,制备了结构为ITO/GO/CH3 NH3 PbI3/PCBM/Ag的平面型器件,对不同GO衬底的器件的光电性能进行表征及对比分析.研究表明:GO衬底缺陷会抑制CH3 NH3 PbI3晶粒的择优取向生长,形成可诱导CH3 NH3 PbI3晶粒产生横向聚集的籽晶,从而改善钙钛矿薄膜的成膜性,并增大钙钛矿晶粒尺寸.由浓度为0.25 mg/mL的分散液制备的GO薄膜衬底上生长的钙钛矿晶粒尺寸最大为900 nm.此外,该浓度对应的GO衬底上制备的钙钛矿薄膜的光致发光相对强度峰值为2000,电荷转移效率相对最高,为52.8％.由该衬底制备的GO基钙钛矿太阳能电池的光电转化效率最高可提升至8.69％.     

Combining Efficiency and Stability in Mixed Tin–Lead Perovskite Solar Cells by Capping Grains with an Ultrathin 2D Layer

The development of narrow-bandgap (E_g ≈ 1.2 eV) mixed tin–lead (Sn–Pb) halide perovskites enables all-perovskite tandem solar cells. Whereas pure-lead halide perovskite solar cells (PSCs) have advanced simultaneously in efficiency and stability, achieving this crucial combination remains a challenge in Sn–Pb PSCs. Here, Sn–Pb perovskite grains are anchored with ultrathin layered perovskites to overcome the efficiency-stability tradeoff. Defect passivation is achieved both on the perovskite film surface and at grain boundaries, an approach implemented by directly introducing phenethylammonium ligands in the antisolvent. This improves device operational stability and also avoids the excess formation of layered perovskites that would otherwise hinder charge transport. Sn–Pb PSCs with fill factors of 79% and a certified power conversion efficiency (PCE) of 18.95% are reported—among the highest for Sn–Pb PSCs. Using this approach, a 200-fold enhancement in device operating lifetime is achieved relative to the nonpassivated Sn–Pb PSCs under full AM1.5G illumination, and a 200 h diurnal operating time without efficiency drop is achieved under filtered AM1.5G illumination.     

Nanoporous p-type NiOx electrode for p-i-n inverted perovskite solar cell toward air stability

Designing air-stable perovskite solar cells (PSCs) is a recent trend in low-cost photovoltaic technology. Metal oxide-based electron transporting layers (ETLs) and hole transporting layers (HTLs) have attracted tremendous attention in PSCs, because of their excellent air stability, high electron mobility, and optical transparency. Herein, we report a co-precipitation method for the synthesis of p-type nanoporous nickel oxide (np-NiOx) thin films as the HTL for inverted (p-i-n) PSCs. The best-performing p-i-n PSC having np-NiOx HTL, (FAPbI₃)_0.85(MAPbBr₃)_0.15 (herein FAPbI₃ stands for formamidinium lead iodide and MAPbBr₃ stands for methylammonium lead bromide) perovskite and phenyl-C₆₁-butyric acid methyl ester (PCBM)/ZnO ETL exhibited a 19.10% (±1%) power conversion efficiency (PCE) with a current density (J_SC) of 22.76?mA?cm^?2, open circuit voltage (V_OC) of 1.076?V and fill factor (FF) of 0.78 under 1?sun (100?mW?cm^?2). Interestingly, the developed p-i-n PSCs based on p-type NiOx and n-type ZnO could retain >80% efficiency after 160?days, which is much higher than conventional PEDOT:PSS HTL-based PSCs. Our findings provide air-stable perovskite solar cells with high efficiency.     

Progress in Materials Development for the Rapid Efficiency Advancement of Perovskite Solar Cells

The efficiency of perovskite solar cells (PSCs) has undergone rapid advancement due to great progress in materials development over the past decade and is under extensive study. Despite the significant challenges (e.g., recombination and hysteresis), both the single‐junction and tandem cells have gradually approached the theoretical efficiency limit. Herein, an overview is given of how passivation and crystallization reduce recombination and thus improve the device performance; how the materials of dominant layers (hole transporting layer (HTL), electron transporting layer (ETL), and absorber layer) affect the quality and optoelectronic properties of single‐junction PSCs; and how the materials development contributes to rapid efficiency enhancement of perovskite/Si tandem devices with monolithic and mechanically stacked configurations. The interface optimization, novel materials development, mixture strategy, and bandgap tuning are reviewed and analyzed. This is a review of the major factors determining efficiency, and how further improvements can be made on the performance of PSCs.     

Dopant-Free Polymer Hole Transport Materials for Highly Stable and Efficient CsPbI3 Perovskite Solar Cells

All-inorganic perovskite CsPbI₃ contains no volatile organic components and is a thermally stable photoactive material for wide-bandgap perovskite solar cells (PSCs); however, CsPbI₃ readily undergoes undesirable phase transitions due to the hygroscopic nature of the ionic dopants used in commonly used hole transport materials. In the current study, the popular donor material PM6 in organic solar cells is used as a hole transport layer (HTL). The benzodithiophene-based backbone-conjugated polymer requires no dopant and leads to a higher power conversion efficiency (PCE) than 2,2′,7,7′-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9′-spirobifluorene (Spiro-OMeTAD). Moreover, PM6 also shows priorities in hole mobility, hydrophobicity, cascade energy level alignment, and even defect passivation of perovskite films. With PM6 as the dopant-free HTL, the PSCs achieve a champion PCE of 18.27% with a competitive fill factor of 82.8%. Notably, the present PCE is based on the dopant-free HTL in CsPbI₃ PSCs reported thus far. The PSCs with PM6 as the HTL retain over 90% of the initial PCE stored in a glovebox filled with N₂ for 3000 h. In contrast, the PSCs with Spiro-OMeTAD as the HTL maintain ≈80% of the initial PCE under the same conditions.     

A Newly Crosslinked-double Network PEDOT:PSS@PEGDMA toward Highly-Efficient and Stable Tin-Lead Perovskite Solar Cells

Until now, poly(3,4-ethylenedioxythiophene):poly(styrensulfonate) (PEDOT:PSS) is widely used in Sn–Pb perovskite solar cells (PSCs) due to its many advantages, including high optical transparency, suitable conductivity, superior wettability, and so on. However, the acidic and hydroscopic properties of the PSS component, as well as the incongruous energy level of the hole transport layer (HTL), may lead to unsatisfying interface properties and decreased device performance. Herein, by adding polyethylene glycol dimethacrylate (PEGDMA) into PEDOT:PSS, a newly crosslinked-double-network obtain of PEDOT:PSS@PEGDMA film, which could not only optimize nucleation and crystallinity of Sn–Pb perovskite films, but also suppress defect density and optimize energy level alignment at the HTL/perovskite interface. As a result, the achieves highly efficient and stable mixed Sn–Pb PSCs with an encouraging power conversion efficiency of 20.9%. Additionally, the device can maintain good stability under N₂ atmosphere.     

Bidirectional Anions Gathering Strategy Afford Efficient Mixed Pb?Sn Perovskite Solar Cells

Mixed lead-tin (Pb Sn) perovskite solar cells (PSCs) possess low toxicity and adjustable bandgap for both single-junction and all-perovskite tandem solar cells. However, the performance of mixed Pb Sn PSCs still lags behind the theoretical efficiency. The uncontrollable crystallization and the resulting structural defect are important reasons. Here, the bidirectional anions gathering strategy (BAG) is reported by using Methylammonium acetate (MAAc) and Methylammonium thiocyanate (MASCN) as perovskite bulk additives, which Ac⁻ escapes from the perovskite film top surface while SCN⁻ gathers at the perovskite film bottom in the crystallization process. After the optoelectronic techniques, the bidirectional anions movement caused by the top-down gradient crystallization is demonstrated. The layer-by-layer crystallization can collect anions in the next layer and gather at the broader, enabling a controllable crystallization process, thus getting a high-quality perovskite film with better phase crystallinity and lower defect concentration. As a result, PSCs treated by the BAG strategy exhibit outstanding photovoltaic and electroluminescent performance with a champion efficiency of 22.14%. Additionally, it demonstrates excellent long-term stability, which retains ≈92.8% of its initial efficiency after 4000 h aging test in the N₂ glove box.     

In Situ Back‐Contact Passivation Improves Photovoltage and Fill Factor in Perovskite Solar Cells

Organic–inorganic hybrid perovskite solar cells (PSCs) have seen a rapid rise in power conversion efficiencies in recent years; however, they still suffer from interfacial recombination and charge extraction losses at interfaces between the perovskite absorber and the charge–transport layers. Here, in situ back‐contact passivation (BCP) that reduces interfacial and extraction losses between the perovskite absorber and the hole transport layer (HTL) is reported. A thin layer of nondoped semiconducting polymer at the perovskite/HTL interface is introduced and it is shown that the use of the semiconductor polymer permits—in contrast with previously studied insulator‐based passivants—the use of a relatively thick passivating layer. It is shown that a flat‐band alignment between the perovskite and polymer passivation layers achieves a high photovoltage and fill factor: the resultant BCP enables a photovoltage of 1.15 V and a fill factor of 83% in 1.53 eV bandgap PSCs, leading to an efficiency of 21.6% in planar solar cells.     

Synergistic Ionic Liquid in Hole Transport Layers for Highly Stable and Efficient Perovskite Solar Cells

Perovskite solar cells (PSCs) with n-i-p structures often utilize an organic 2,2′,7,7′-tetrakis (N, N-di-p-methoxyphenyl-amine) 9,9′-spirobifluorene (spiro-OMeTAD) along with additives of lithium bis(trifluoromethanesulfonyl)imide salt (LiTFSI) and tert-butylpyridine as the hole transporting layer (HTL). However, the HTL lacks stability in ambient air, and numerous defects are often present on the perovskite surface, which is not conducive to a stable and efficient PSC. Therefore, constructive strategies that simultaneously stabilize spiro-OMeTAD and passivate the perovskite surface are required. In this work, it is demonstrated that a novel ionic liquid of dimethylammonium bis(trifluoromethanesulfonyl)imide (DMATFSI) could act as a bifunctional HTL modulator in n-i-p PSCs. The addition of DMATFSI into spiro-OMeTAD can effectively stabilize the oxidized spiro-OMeTAD⁺ cation radicals through the formation of spiro-OMeTAD⁺TFSI⁻ because of the excellent charge delocalization of the conjugated CF₃SO₂⁻ moiety within TFSI⁻. In addition, DMA⁺ cations could move toward the perovskite from the HTL, resulting in the passivation of defects at the perovskite surface. Accordingly, a power conversion efficiency of 23.22% is achieved for PSCs with DMATFSI and LiTFSI co-doped spiro-OMeTAD. Moreover, benefiting from the improved ion migration barrier and hydrophobicity of the HTL, still retained nearly 80% of their initial power conversion efficiency after 36 days of exposure to ambient air.     

倒置钙钛矿太阳能电池的空穴传输层的研究进展

倒置钙钛矿太阳能电池(PSCs)具有器件结构简单、吸光系数高、迟滞效应小、良好的缺陷容忍性等优点,受到了广泛的关注。但倒置器件光电转换效率(PCE)尚有待提高,究其原因是空穴传输层(HTL)和钙钛矿层界面处的能量损失表现出相对较小的开路电压。文章综述了包括有机聚合物、无机物、尖晶石氧化物等作为空穴传输材料的相关研究进展,进一步分析了通过调节电极/空穴传输层能级使之与钙钛矿价带匹配,及通过界面修饰促进器件对载流子的注入与收集,从而提高光电转换效率的研究现状。对提高倒置钙钛矿太阳能电池性能的研究具有一定的指导意义,最后对倒置器件的应用前景进行了展望。     

Highly stable carbon-based perovskite solar cell with a record efficiency of over 18% via hole transport engineering

Carbon-based perovskite solar cells show great potential owing to their low-cost production and superior stability in air, compared to their counterparts using metal contacts. The photovoltaic performance of carbon-based PSCs, however, has been progressing slowly in spite of an impressive efficiency when they were first reported. One of the major obstacles is that the hole transport materials developed for state-of-the-art Au-based PSCs are not suitable for carbon-based PSCs. Here, we develop a low-temperature, solution-processed Poly(3-hexylthiophene-2,5-diyl) (P3HT)/graphene composite hole transport layer (HTL), that is compatible with paintable carbon-electrodes to produce state-of-the-art perovskite devices. Space-charge-limited-current measurements reveal that the as-prepared P3HT/graphene composite exhibits outstanding charge mobility and thermal tolerance, with hole mobility increasing from 8.3 × 10⁻³ cm² V^-1 s^-1 (as-deposited) to 1.2 × 10^-2 cm² V^-1 s^-1 (after annealing at 100 °C) - two orders of magnitude larger than pure P3HT. The improved charge transport and extraction provided by the composite HTL provides a significant efficiency improvement compared to cells with a pure P3HT HTL. As a result, we report carbon-based solar cells with a record efficiency of 17.8% (certified by Newport); and the first perovskite cells to be certified under the stabilized testing protocol. The outstanding device stability is demonstrated by only 3% drop after storage in ambient conditions (humidity: ca. 50%) for 1680 h (non-encapsulated), and retention of ca. 89% of their original output under continuous 1-Sun illumination at room-temperature for 600 h (encapsulated) in a nitrogen environment.