Dipartimento di Fisica, Università degli Studi di Cagliari, I-09042 Monserrato, Italy.
Istituto di Nanotecnologia CNR-Nanotec, Polo di Nanotecnologia c/o Campus Ecotekne, via Monteroni, 73100 Lecce, Italy.
Sci Rep. 2017 Mar 20;7:44629. doi: 10.1038/srep44629.
Metal-halide perovskite solar cells rival the best inorganic solar cells in power conversion efficiency, providing the outlook for efficient, cheap devices. In order for the technology to mature and approach the ideal Shockley-Queissier efficiency, experimental tools are needed to diagnose what processes limit performances, beyond simply measuring electrical characteristics often affected by parasitic effects and difficult to interpret. Here we study the microscopic origin of recombination currents causing photoconversion losses with an all-optical technique, measuring the electron-hole free energy as a function of the exciting light intensity. Our method allows assessing the ideality factor and breaks down the electron-hole recombination current into bulk defect and interface contributions, providing an estimate of the limit photoconversion efficiency, without any real charge current flowing through the device. We identify Shockley-Read-Hall recombination as the main decay process in insulated perovskite layers and quantify the additional performance degradation due to interface recombination in heterojunctions.
金属卤化物钙钛矿太阳能电池在能量转换效率方面可与最好的无机太阳能电池相媲美，为高效、廉价的设备提供了前景。为了使该技术成熟并接近理想的肖克利-奎塞尔效率，需要实验工具来诊断除了通过经常受到寄生效应影响且难以解释的电特性测量之外，哪些过程限制了性能。在这里，我们使用全光学技术研究了导致光转换损耗的复合电流的微观起源，该技术测量了电子-空穴自由能作为激发光强度的函数。我们的方法可以评估理想因子，并将电子-空穴复合电流分解为体缺陷和界面贡献，在没有任何实际电荷电流流过器件的情况下，提供对极限光转换效率的估计。我们确定了在绝缘钙钛矿层中的肖克利-里德-霍尔复合是主要的衰减过程，并量化了异质结中界面复合引起的额外性能下降。
