Davies Christopher L, Filip Marina R, Patel Jay B, Crothers Timothy W, Verdi Carla, Wright Adam D, Milot Rebecca L, Giustino Feliciano, Johnston Michael B, Herz Laura M
Department of Physics, University of Oxford, Clarendon Laboratory, Parks Road, Oxford, OX1 3PU, UK.
Department of Materials, University of Oxford, Parks Road, Oxford, OX1 3PH, UK.
Nat Commun. 2018 Jan 18;9(1):293. doi: 10.1038/s41467-017-02670-2.
Photovoltaic devices based on metal halide perovskites are rapidly improving in efficiency. Once the Shockley-Queisser limit is reached, charge-carrier extraction will be limited only by radiative bimolecular recombination of electrons with holes. Yet, this fundamental process, and its link with material stoichiometry, is still poorly understood. Here we show that bimolecular charge-carrier recombination in methylammonium lead triiodide perovskite can be fully explained as the inverse process of absorption. By correctly accounting for contributions to the absorption from excitons and electron-hole continuum states, we are able to utilise the van Roosbroeck-Shockley relation to determine bimolecular recombination rate constants from absorption spectra. We show that the sharpening of photon, electron and hole distribution functions significantly enhances bimolecular charge recombination as the temperature is lowered, mirroring trends in transient spectroscopy. Our findings provide vital understanding of band-to-band recombination processes in this hybrid perovskite, which comprise direct, fully radiative transitions between thermalized electrons and holes.
基于金属卤化物钙钛矿的光伏器件效率正在迅速提高。一旦达到肖克利-奎塞尔极限，电荷载流子的提取将仅受电子与空穴的辐射双分子复合限制。然而，这一基本过程及其与材料化学计量的联系仍未得到充分理解。在这里，我们表明，甲基碘化铅钙钛矿中的双分子电荷载流子复合可以完全解释为吸收的逆过程。通过正确考虑激子和电子-空穴连续态对吸收的贡献，我们能够利用范·罗斯布鲁克-肖克利关系从吸收光谱中确定双分子复合速率常数。我们表明，随着温度降低，光子、电子和空穴分布函数的锐化显著增强了双分子电荷复合，这与瞬态光谱中的趋势一致。我们的发现为这种混合钙钛矿中的带间复合过程提供了至关重要的理解，该过程包括热化电子和空穴之间的直接、完全辐射跃迁。
