一步溶液法制备有机-无机杂化钙钛矿薄膜

有机-无机杂化钙钛矿薄膜作为太阳电池的光吸收层,其薄膜的形貌、结构以及结晶程度等因素对电池的光电转换效率起到了决定性的作用,而薄膜的质量主要取决于制备工艺.采用一步溶液法制备了有机-无机杂化钙钛矿(CH3NH3PbI3)薄膜,主要分析了在氟掺杂氧化锡(FTO)导电玻璃、玻璃和多晶硅3种不同衬底上生长CH3NH3PbI3薄膜的形貌和结构的差异.结果表明,在FTO导电玻璃和玻璃衬底上生长的薄膜的晶粒尺寸和晶粒分布均匀,而在硅衬底上生长的薄膜的边缘晶粒尺寸大于中心处的晶粒,并详细分析了造成这种现象的原因.此外,在50℃的低温下对在FTO导电玻璃衬底生长的CH3NH3PbI3薄膜进行了不同时间的退火处理.实验结果表明,随着热处理时间的增加,晶粒尺寸也增加,但是合成的CH3NH3PbI3薄膜部分发生了分解.     

CH3NH3PbI3钙钛矿太阳电池晶粒尺寸及光电性能调控

钙钛矿薄膜的晶粒尺寸对器件性能影响很大。采用湿润性不同的空穴传输层以及不同浓度的CH3NH3I（MAI）溶液,使用热退火和溶剂气氛退火的方法制备出CH3NH3PbI3薄膜及相应电池。测量了不同制备条件的钙钛矿薄膜的X射线衍射、扫描电子显微镜、光致发光谱,以及器件的电流密度-电压曲线。结果表明,溶剂气氛退火可以有效地增大薄膜的晶粒尺寸,提高器件的电流密度;较高浓度的MAI能将PbI2完全转化为CH3NH3PbI3,增大晶粒尺寸;不湿润的功函数更高的空穴传输层有利于电池效率的提高。制备了最高效率为13.3%的CH3NH3PbI3钙钛矿电池,为制备更大晶粒的钙钛矿薄膜与更高效率的钙钛矿太阳电池奠定了基础。     

用溶液法制备钙钛矿纳米线光电探测器

作为一种优秀的光吸收半导体材料,有 机-无机杂化钙钛矿被广泛应用于光电领域。为了制备高 性能光电探测器件,采用溶液法制备了高度有序、超长的CH3NH3PbI3 纳米线,并将其应用于Au/CH3NH3PbI3/Au平面型光电探测器。该 器件具有宽的工作波段,在紫外-可见光-近红外(365~808 nm) 光谱范围内均有响应。其最大光响应度达到3.81 A·W-1,比探 测率为3.7×1011 Jones,开关比为4.9×103,光响应时间约 为7 ms。由于具有优异的光探测能力,该器件拥有广阔的应用前景。     

CH3NH3PbI3/p-Si异质结的光电特性研究

利用一步溶液法在p型Si衬底上生长有机/无机杂化钙钛矿CH3NH3PbI3薄膜,构成CH3NH3PbI3/p-Si异质结。利用原子力显微镜(AFM)、扫描电子显微镜(SEM)对薄膜形貌和结构进行表征,通过无光照和有光照条件下的电流-电压(I-V)、电容-电压(C-V)测试对异质结的光电特性进行研究。I-V测试结果显示CH3NH3PbI3/p-Si异质结具有整流特性,正反偏压为±5V时,整流比大于70,并在此异质结上观察到了光电转换现象,开路电压为10mV,短路电流为0.16uA。C-V测试结果显示Ag/CH3NH3PbI3/p-Si异质结具有与MIS(金属-绝缘层-半导体)结构相似的C-V特性曲线,与理想MIS的C-V特性曲线相比,异质结的C-V曲线整体沿电压轴向正电压方向平移。C-V特性曲线的这种平移表明Ag/CH3NH3PbI3/p-Si异质结界面存在界面缺陷,CH3NH3PbI3层也可能存在固定电荷。这种界面缺陷是导致CH3NH3PbI3/p-Si异质结开路电压的大幅度降低的重要原因。此外,CH3NH3PbI3薄膜的C-V测试结果显示其具有介电非线性特性,其介电常数约为4.64。     

PbI2掺杂对CH3NH3PbI3光电性能的影响

采用溶液生成法制备了有机铅卤化钙钛矿(CH3 NH3PbI3)晶体粉末,并以过量的PbI2对其进行掺杂,采用X射线衍射谱(XRD)技术研究了掺杂前后样品的晶体结构变化.表面光电压谱(SPS)和相位谱(PS)显示掺杂前后的CH3 NH3 PbI3均为p型半导体,但后者有更强的光伏响应.场诱导表面光电压谱(FISPS)表明:当加正电场时,掺杂前后的CH3NH3PbI3均表现为p型半导体的载流子特性,当加负偏压时掺杂后的CH3NH3PbI3易形成反型层,出现光伏反转,且外加负偏压越大,光伏反转区域越大,表现出双极导电特性.     

空气环境中不同反溶剂对CH_3NH_3PbI_3钙钛矿太阳电池光电性能的影响研究

在一步溶液法制备钙钛矿薄膜的工艺中,溶剂环境是决定薄膜质量的关键因素。本文以全空气环境中,甲苯、氯苯、乙醚、乙酸乙酯这四种常见的反溶剂为研究对象,重点比较研究了不同反溶剂对钙钛矿多晶薄膜的结晶性、形貌、覆盖率以及器件光电转换效率的影响。研究表明:在相对湿度(RH)高达70%的环境下,相较于其他三种反溶剂,乙酸乙酯不仅能控制钙钛矿薄膜的结晶速率,还表现出优异的抗湿性,因此钙钛矿电池的效率达到17.8%,明显优于使用其他反溶剂。     

提高薄膜太阳能电池光谱响应的光学结构设计

光吸收效率是提高薄膜太阳能电池的光电转换效率的关键,通过增加入射光在太阳能电池中的光程的方法提升电池的吸收效率。采用有限元法对薄膜太阳能电池进行参数和结构优化。首先设计了一维具有分布式布拉格反射器性能,波长范围在400~800nm的的光子晶体DBR结构作为电池的背反射,与单纯的PIN结构的太阳能电池相比,使光吸收效率和光谱响应分别提升了38%和45%,并在此基础上,在DBR表面刻蚀光栅作为薄膜硅太阳能电池的背底反射器。仿真结果表明:通过利用DBR的高反射性和光栅的衍射作用,在400~1 000nm光谱范围内,进一步提高了太阳能电池的光吸收效率和光谱响应,通过与单纯PIN太阳能电池相比较,光吸收率和光谱响应分别提升了61.6%,和85.4%。     

两步沉积法制备锡基钙钛矿及其全溶液工艺太阳能电池性能

两步沉积法中胺盐的传统溶剂异丙醇会对锡基钙钛矿产生严重破坏,因此探索其他溶剂制备锡基钙钛矿非常重要。利用4-甲基-2-戊醇取代异丙醇充当胺盐的溶剂,并在胺盐中添加苯乙基溴化胺(PEABr),通过两步沉积法制备了锡基钙钛矿薄膜及全溶液工艺太阳能电池。实验结果表明,相比于异丙醇,使用4-甲基-2-戊醇作为胺盐溶剂,可降低对锡基钙钛矿的破坏作用,促进锡基钙钛矿结晶成膜,原因可能是该溶剂分子的烷基部分可以增加对羟基的空间位阻。但未添加PEABr时,制备的FASnI₃薄膜存在许多针孔,器件光电转换效率(PCE)仅为0.24%;在添加摩尔占比为0.3 (n (PEABr)/n (FAI+PEABr)=0.3)的PEABr时,制备的锡基钙钛矿薄膜针孔减少,致密度提高,表面形貌得到改善。利用全溶液工艺制备的基于该薄膜的太阳能电池PCE达到4.15%。该研究有助于促进两步沉积法制备锡基钙钛矿薄膜及其光伏器件的进一步发展。     

空气环境中湿度对钙钛矿太阳能电池微观形貌与光电效率的影响

有机无机卤化钙钛矿太阳能电池中钙钛矿吸收层对外界的湿度非常敏感,所以目前绝大多数钙钛矿太阳能电池的制备、封装都是在手套箱中完成的。从便于工业规模化角度,在全空气环境下,采用气相辅助溶液法制备了平板结构的钙钛矿太阳能电池,研究了外界湿度与钙钛矿膜形貌、电池效率之间的关系。通过比较研究发现:在全空气环境中,湿度从70%下降为20%时,电池的转换效率从0.95%增加到5.81%。分析认为湿度的降低,增加了钙钛矿膜的覆盖率以及减少膜的缺陷,改善了电池开路电压、短路电流等性能参数。     

石墨烯材料在钙钛矿太阳能电池中的研究进展

石墨烯及其衍生物具有独特的材料结构和光电性质,可作为界面修饰层、电子传输层、空穴传输层应用于新型钙钛矿太阳能电池,以提高电池的光电转换效率和性能稳定性。此外,石墨烯透明电极在柔性、半透明或叠层钙钛矿太阳能电池应用中独具优势。本文综述了石墨烯及其衍生物在钙钛矿太阳能电池中的研究进展,指出了未来发展重点。     

Self-assembled monolayers in perovskite solar cells

Perovskite solar cells (PSCs) have attracted great atten-tion due to excellent power conversion efficiency (PCE),low cost and simple solution processing.The certified PCE has reached 25.5％ from the initial efficiency of 3.8％,being com-parable to that of commercial crystalline silicon solar cells[1,2].The efficiency boosting is mainly ascribed to the excellent properties of halide perovskite materials,including suitable bandgaps,high absorption coefficient,long carrier diffusion length and high defect tolerance[3].Moreover,through the composition and interface engineering,the operational sta-bility of PSCs can exceed 1000 h under continuous illumina-tion[4].Therefore,PSCs show a great promise for commerciali-zation.     

Solvent engineering of the electron transport layer using 1,8-diiodooctane for improving the performance of perovskite solar cells

In this work, the power conversion efficiency (PCE) of perovskite solar cells (PSCs) was improved by 14.8% (from 11.09% to 12.73%) by using 1,8-diiodooctane (DIO) as a solvent additive during the deposition of phenyl-C61-butyric acid methyl ester (PCBM) layers. The primary reasons for the PCE improvement are the simultaneous increases in the short-circuit current density, fill factor, and open-circuit voltage. The incorporation of DIO improves the morphology of the electron transport layer (PCBM), which plays an important role in charge dissociation, transportation, and collection. Our results indicate that engineering the morphology of the electron transport layer is a simple and effective method for developing high-performance PSCs.     

Renaissance of tin halide perovskite solar cells

Halide perovskite solar cells(PSCs)have attracted wide interests in photovoltaics field due to the prominent advantages of perovskite materials.To date,the certified power conversion efficiency(PCE)of lead-based PSCs has reached to 25.5%[1].However,the toxicity of lead in PSCs limits the practical application.Tin(Sn)-based perovskites are the most promising candidates because of their narrow bandgap and comparable optoelectronic properties to lead analogues.     

Polymer additive assisted crystallization of perovskite films for high-performance solar cells

Perovskite solar cells (PSCs) have attracted much attention as a novel photoelectric converter. The quality of perovskite films plays a key role in the efficiency and stability. Among them, defects in the films surface restrict the performance of solar cells. Surface passivation is an effective route to eliminate defect of perovskite films. In this paper, we introduce PVB as a novel polymer additive, it can assist perovskite films with better crystallinity and morphology, as well as less defects. Perovskite solar cells with 1.5 mg/mL optimized concentration PVB exhibit power conversion efficiency (PCE) of 19.04% than 16.34% of control cells. Meanwhile, the cells with PVB demonstrate less hysteresis than that without additive, as well as excellent reproducibility. Additionally, perovskite solar cells based on PVB can retain around 90% of its original efficiency under fully ambient air of 65 ± 5% relative humidity or under 65 °C after aging for 30 days. The finding provides a potential additive candidate for fabrication of higher performance devices.     

Ion migration in perovskite solar cells

The past few years have witnessed a remarkable progress of perovskite solar cells(PSCs),which can be attributed to the high light absorption coefficient,tunable bandgap,long carrier diffusion length,solution processability at low temperature and relatively low cost of perovskite materials.     

Bifunctional-based small molecule as multifunctional additive for improved performance of perovskite solar cells

Hybrid perovskites have great potential as light-absorbing materials, while its degradation of poor crystallization and ion migration have been the major obstacle in perovskite solar cells (PSCs). Herein, the bifunctional-based small molecule dicyandiamide (DCD) was applied as additive in the PSCs. The amino and cyano group of DCD could effectively control crystallization and passivating grain defects, resulting in the high-quality perovskite films with large grain size. In addition, the adding of DCD increases the film conductivity of perovskite active layer, which is beneficial for charge transport in perovskite film. The DCD added PSCs shows an optimal power conversion efficiency (PCE) of 19.08% with negligible hysteresis. Furthermore, the long-term stability of PSCs is significantly enhanced. The results indicate that the device's integrative performance could be efficiently improved by the synergistic effect of amino and cyano functional groups, meaning that the addition of DCD into perovskite precursor could enable this optimization.     

Improvement and Regeneration of Perovskite Solar Cells via Methylamine Gas Post‐Treatment

The control of film morphology is crucial in achieving high‐performance perovskite solar cells (PSCs). Herein, the crystals of the perovskite films are reconstructed by post‐treating the MAPbI₃ devices with methylamine gas, yielding a homogeneous nucleation and crystallization of the perovskite in the triple mesoscopic inorganic layers structured PSCs. As a result, a uniform, compact, and crystalline perovskite layer is obtained after the methylamine gas post‐treatment, yielding high power conversion efficiency (PCE) of 15.26%, 128.8% higher than that of the device before processing. More importantly, this post‐treatment process allows the regeneration of the photodegraded PSCs via the crystal reconstruction and the PCE can recover to 91% of the initial value after two cycles of the photodegradation‐recovery process. This simple method allows for the regeneration of perovskite solar cells on site without reconstruction or replacing any components, thus prolonging the service life of the perovskite solar cells and distinguishing from any other photovoltaic devices in practice.     

Applications of cesium in the perovskite solar cells

Perovskite solar cells have experienced an unprecedented rapid development in the power conversion efficiency (PCE) during the past 7 years, and the record PCE has been already comparable to the traditional polycrystalline silicon solar cells. Presently, it is more urgent to address the challenge on device stability for the future commercial application. Recently, the inorganic cesium lead halide perovskite has been intensively studied as one of the alternative candidates to improve device stability through controlling the phase transition. The cesium (Cs)-doped perovskites show more superior stability comparing with organic methylammonium (MA) lead halide perovskite or formamidinium (FA) lead halide perovskite. Here, recent progress of the inorganic cesium application in organic-inorganic perovskite solar cells (PSCs) is highlighted from the viewpoints of the device efficiency and the device stability.     

Fused-ring electron acceptor as an efficient interfacial material for planar and flexible perovskite solar cells

Perovskite solar cell (PSC) has attracted great attention due to its high power conversion efficiency (PCE), low cost and solution processability. The well-designed interface and the modification of electron transport layer (ETL) are critical to the PCE and long-term stability of PSCs. In this article, a fused-ring electron acceptor is employed as the interfacial material between TiO₂ and the perovskite in rigid and flexible PSCs. The modification improves the surface of TiO₂, which decreases the defects of ETL surface. Moreover, the modified surface has lower hydrophilicity, and thus is beneficial to the growth of perovskite with large grain size and high quality. As a result, the interfacial charge transfer is promoted and the interfacial charge recombination can be suppressed. The highest PCE of 19.61% is achieved for the rigid PSCs after the introduction of ITIC, and the hysteresis effect is significantly reduced. Flexible PSC with ITIC obtains a PCE of 14.87%, and the device stability is greatly improved. This study provides an efficient candidate as the interfacial modifier for PSCs, which is compatible with low-temperature solution process and has a great practical potential for the commercialization of PSCs.     

Double-layered hole transport material of CuInS2/Spiro for highly efficient and stable perovskite solar cells

In this paper, double-layered hole transport material (HTM) was designed and fabricated by adding a thin CuInS₂ film between perovskite and Spiro-OMeTAD (Spiro) layers. The power conversion efficiency (PCE) of the perovskite solar cells (PSCs) with double-layered HTM of CuInS₂/Spiro was improved to 19.63% from 17.97% for the devices with pure Spiro. Moreover, the operational stability of the PSCs with double-layered HTM of CuInS₂/Spiro was enhanced. The PCE of the PSCs with CuInS₂/Spiro retains 91% of the initial value after 30 days storage in ambient atmosphere. The experimental results indicate that the improved performance could be come from the energy band match between CuInS₂ and Spiro, fast hole extraction and transport, and decreased charge recombination in the PSCs with double-layered HTM of CuInS₂/Spiro. This work provides a promising prospect to design a low-cost and high stability HTM for commercial PSCs.