高效稳定全无机钙钛矿电池CsPbI3的材料设计与带隙调控及界面电子结构研究

Recently, the novel inorganic perovskite materials CsPbI3 have triggered a strong interest by researchers due to their excellent photoelectric property and good compositional stability. However, they still have some key issues to be solved so far, such as the structural phase transition and their large band gap. Meanwhile, the film quality, device efficiency, and stability also need to be further improved. In view of above questions, herein a novel Br2-assisted vapor deposition hybrid method is developed for the controllable preparation of CsPbxSn1-x(IyBr1-y)3 light absorbing films in this proposal, in which the Br- doping and Sn2+ alloying strategies are innovatively employed to suppress the phase change and reduce the band gap; and the linearly graded band gap structure is then designed for the fabrication of high-efficient and stable all-inorganic perovskite solar cells, combined with the interface optimization using the new class of inorganic materials ZnO and NiOx. We will systematically study the doping control strategy and the interface engineering of CsPbI3; and mainly focus on the phase change of the crystal structure, the interfacial electronic structure, and the energy level arrangement by using advanced characterizations and the density functional theory calculations; and also explore the relationship between the graded band gap with light absorption, built-in electric field, and dark current, correlated with the device's photovoltaic performance. Based on the successful implementation of this project, it is expected to reveal the phase transition mechanism and the band-gap interaction theory, and provide important theoretical basis for the research and development of high-performance perovskite solar cells.

近期，新型无机钙钛矿材料CsPbI3由于具有优异的光电性能和良好的热稳定性而引起研究者的浓厚兴趣；但目前仍存在结构相变、带隙过宽等关键问题亟待解决，其薄膜质量、器件效率及稳定性也尚待提高。针对上述问题，本项目拟创新性地运用Br-取代和Sn2+固溶策略来抑制相变、降低带隙，采用新颖的Br2辅助气相混合工艺，可控制备CsPbxSn1-x(IyBr1-y)3光吸收层；并对其带隙进行线性梯度结构设计，结合ZnO、NiOx等新型无机材料界面优化，来制备高效稳定的全无机钙钛矿电池。项目将对材料的掺杂调控和器件的界面工程进行系统研究；并采用先进表征手段和密度泛函理论计算，重点研究材料晶体结构相变、界面电子结构及能级排列规律；同时探索梯度带隙与光吸收、内建电场及暗电流的关系，并与器件光伏性能相关联。通过本项目的实施，可望揭示CsPbI3材料相变机理和价带影响机制，为研发高性能钙钛矿电池提供重要的理论依据。

近年来，新型CsPb(IxBr1-x)3无机钙钛矿材料由于具有优异的光电特性和良好的热稳定性而受到广泛关注，可望解决MAPbI3传统钙钛矿电池的稳定性瓶颈问题，因而对研发高效、稳定、低成本的新型光伏电池具有重要意义。但是，由于相关研究才刚开展，在材料设计、能带调控及器件界面研究等方面仍存在巨大潜力空间。本项目创新性地采用Br2辅助气相混合工艺，运用Br-掺杂策略来抑制相变，调整其带隙，制备出高质量CsPb(IxBr1-x)3光吸收层薄膜，进而研制出10%以上的高效稳定无机钙钛矿电池，其中空气中制备的CsPbI3电池效率达到12%，而溶剂工程法制备的CsPbIBr2电池效率高达13.18%。同时，还采用Br2 蒸汽辅助CVD工艺制备出非常稳定的CsPbBr3无机钙钛矿电池；采用CVD气相沉积工艺制备出~18%的高效MAPbI3-xClx钙钛矿电池；通过掺杂及钝化工艺研制出22.54% 的MA0.85FA0.15PbI3钙钛矿电池。此外，还研制出15.69%的柔性CIGS薄膜电池，达到较好水平；制备出高电导、高透光的IZO新型TCO薄膜，进而制备出15.74%的半透明钙钛矿电池；并构筑出柔性CIGS/钙钛矿四端叠层太阳电池，效率达到20.85%。本项目取得了较为一定研究成果：项目共申请专利15项，授权6项；发表论文17篇，其中高水平论文12篇，会议论文5篇，顺利完成预期目标。本项目的成功实施，进一步揭示了CsPbI3材料的相变机理及其抑制机理，研发高性能钙钛矿电池提供了重要的实验及理论依据。而高效稳定的无机钙钛矿电池也可望广泛应用于BIPV光伏建筑一体化、半透明光伏器件及高效叠层太阳电池等领域。