钙钛矿太阳能电池近期进展

Recent research progress in perovskite solar cells

近几年来,基于有机无机金属卤化物钙钛矿(ABX_3)的太阳能电池由于其独特的物理化学性质受到了广泛的关注.这种钙钛矿材料具有很高的消光系数、较强的电荷传递能力、长的载流子寿命、长的载流子扩散距离以及特殊的双极性,同时低成本易制作.自2009年至今,钙钛矿太阳能电池的光电转换效率从最初的3.8%增长到了20.8%,使之成为最有可能在未来代替传统单晶硅太阳能电池的新型太阳能电池.同时,由于钙钛矿具有双极性,故钙钛矿太阳能电池的结构也有多种,最常见的结构有介孔结构、平面结构、介观超结构、无空穴传输层结构等.本文主要介绍钙钛矿太阳能电池的发展、电池结构及其对光电池性能的影响、钙钛矿薄膜的制备方法,同时探讨了钙钛矿在电子传输层上的吸附模型和电荷在电池界面中的传输机理以及界面工程,并介绍该类型电池在近期所获得的突破及未来可能的发展方向,以便对钙钛矿太阳能电池有进一步的了解.

Recently, all-solid state hybrid solar cells based on organic-inorganic metal halide perovskite（ABX3） materials have received much attention from the academic circle all over the world due to their unique physical and chemical properties.The perovskite materials exhibit advantages of high extinction coefficient, high charge mobility, long carrier lifetime, and long carrier diffusion distance. Furthermore, they are low cost and easily synthesized. The power conversion efficiency（PCE） has exceeded 20.8% since the PCE of 3.8% was first reported in 2009, making the perovskite solar cells the best potential candidate of the new generation solar cells to replace the high-cost and highly polluting silicon solar cells in the future. Meanwhile, because of the well-known special bipolar properties of the perovskite materials, various structures are designed such as the all-solid state mesoscopic heterojunctions, planar-heterojunctions, meso-superstructures, and HTM-free structures. In this review, we first introduce the development of the perovskite solar cells and then focus on the cell structure and its influence on the cell performance. Besides, the synthesis methods of the perovskite films and the performance characteristics and advantages of the perovskite solar cells with different cell structures are also discussed. It is found that although the perovskite crystals prepared by a one-step spin-coating method have bigger grain sizes, their morphologies are rougher and uncontrollable, which may suppress the charge carrier extraction efficiency and lead to a relatively low power conversion efficiency. Meanwhile, vapor-assisted method needs vaccum conditions, which significantly increases the manufacture cost of PSC. Compared with these methods mentioned above, solution-based sequential deposition method can not only enhance the reproducibility of PSC, but also obtain a higher PCE with a lower cost. Afterwards, the photogenerated carrier transport mechanism of the perovskite solar cells is discussed. The possible atomic interaction model and the electron structure between perovskite film and electron transport layer are proposed. There are two possible interface atomic structures at the interface of perovskite CH3NH3 Pb I3and TiO2.It is supposed that the interaction between iodine atoms and titanium atoms dominates the atomic structure at the interface of CH3NH3 Pb I3and TiO2, while the lead atoms are believed to bond to oxygen atoms. As is well known,charge extraction, transfer and recombination mainly occur at the interface of a cell. Therefore, the interface engineering including the design for energy level matching is important and necessary to enhance the charge transport efficiency,suppress the charge recombination and eventually improve the performance of perovskite solar cells. Moreover, the properties of the main electron transport layer（ZnO, TiO2, PCBM, Al2O3） and hole transport layer（spiro-OMe TAD,P3 HT, NiO, PTAA） and their influences on the PCE of the perovskite solar cells are discussed. The main challenges of the all-solid state hybrid perovskite solar cells such as environment pollution, the extremely small working areas and the instability are introduced. Finally, the development prospects of perovskite solar cells in the future are proposed in order to have a better understanding of the perovskite solar cells.