基于全杂化钙钛矿的高效叠层太阳能电池开发及性能研究

Recently, organic-inorganic hybrids perovskite solar cell has received intensive attention, due to its rapidly increasing power conversion efficiency (over 20%), low cost and ease of fabrication. Tandem (multi-junction) solar cell technology, where the sub-cells connect with each other in series to release the thermalization loss of hot carriers generated by photons with larger energy than the bandgap (Eg), has proven to be a promising strategy to further boost the PCE, which can break the limit of the theoretical maximum efficiency of single junction photovoltaic cells. The successful demonstration of perovskite-perovskite tandem solar cell, could not only lead to a photovoltaic technology with both low cost and high performance, but also benefit the deep understanding of the bend bending, optical/electric distribution and carrier transportation mechanism in the corresponding device. In this proposal, hybrids perovskite based tandem solar cells are proposed. Efforts are focused to address several major issues that are critical in developing perovskite tandem devices including: 1) film growth of perovskite layers with tunable bandgap on the front perovkite solar cell; 2) rational design of the tunneling junction; 3) demonstration of two terminal perovksite-perovskite tandem solar cell with high performance. The outcome of the proposed research will provide sufficient evidence and experimental data to support theoretical design and eventually pave the way for the practical use of perovskite tandem solar cells.

近年来，有机无机钙钛矿太阳能电池由于其光电转换效率高(>20%)、成本低廉以及制备工艺简单，被视为最有潜力的新一代光伏技术。叠层太阳能电池技术采用两节（或多节）电池分步吸收太阳光，从而减少热电子的损耗，进一步提高光电转换效率，突破Shockley-Queisser理论极限。将叠层电池技术应用于全钙钛矿材料体系有望同时解决现有技术中存在的成本高或效率低等问题；并且可在理论上丰富界面能级结构，光场／电场结构，载流子微观传输机制等基础问题研究。本项目拟开发基于全钙钛矿材料的二电极叠层太阳能电池。拟解决的核心科学与技术问题包括：1）在前节钙钛矿太阳能电池上生长窄带隙钙钛矿材料并调控其带隙；2）开发合适的隧道结材料及制备工艺；3）构筑二电极的全钙钛矿高效叠层太阳能电池并研究工作机理。该研究将为高效能、低成本的器件制备提供理论依据和实验论证，从而推动钙钛矿太阳能电池技术的实用化。

近年来，有机无机杂化钙钛矿太阳能电池得到了学术界和工业界的广泛关注。钙钛矿材料具有优异的光电学特性，其单结电池的光电转换效率已经超过了25%，且钙钛矿的光学带隙可通过改变其组分而进行调控，非常有望构筑高效的全钙钛矿叠层太阳能电池器件。在本项目执行期间，我们以制备得到高效率高稳定性的全钙钛矿叠层太阳能电池为主要目标，主要进行了以下研究工作：（1）设计并优化了宽带隙钙钛矿组分体系；系统研究了电池光电转换效率与钙钛矿薄膜缺陷态、结晶态、相态等之间的联系及内在机理；（2）设计并成功制备了与宽带隙钙钛矿体系相匹配的窄带隙钙钛矿体系，并对钙钛矿薄膜的表界面进行钝化处理，降低了薄膜的缺陷态密度，提升了其对氧气的抵抗能力，实现了相应单结太阳能电池效率及稳定性的共同提升；（3）设计了两种连接宽带隙和窄带隙钙钛矿子电池的隧道结结构，并引入高分子功能层以抵抗溶剂侵蚀，成功构筑了四电极同质钙钛矿叠层太阳能电池与二电极的全钙钛矿的叠层太阳能电池；（4）创新性地提出了基于循环“氧化还原梭”的缺陷修复策略与表面疏水修饰策略，极大延长了铅卤钙钛矿材料及器件在工况条件下的本征稳定性。这一系列创新有力推进了新一代光伏技术的发展，得到了学术界和工业界的广泛认可。