Strain-induced rubidium incorporation into wide-bandgap perovskites reduces photovoltage loss
Likai Zheng, Mingyang Wei, Felix T. Eickemeyer, Jing Gao, Bin Huang, Ummugulsum Gunes, Pascal Schouwink, David Wenhua Bi, Virginia Carnevali, Mounir Mensi, Francesco Biasoni, Yuxuan Zhang, Lorenzo Agosta, Vladislav Sláma, Nikolaos Lempesis, Michael A. Hope, Shaik M. Zakeeruddin, Lyndon Emsley, Ursula Röthlisberger, Lukas Pfeifer, Yimin Xuan, Michaël Grätzel
Abstract
A-site cation mixing can enhance the photovoltaic performance of a wide-bandgap (WBG) perovskite, but rubidium (Rb) cation mixing generally forms a nonperovskite phase. We report that lattice strain locks Rb ions into the α-phase of the lattice of a triple-halide WBG perovskite, preventing phase segregation into a nonperovskite Rb-cesium–rich phase. This process cooperates with chloride accommodation and promotes halide homogenization across the entire film volume. The resulting 1.67–electron volt WBG perovskite exhibits photoluminescence quantum yields exceeding 14% under 1-sun-equivalent irradiation, corresponding to a quasi–Fermi level splitting of ~1.34 electron volts. A WBG perovskite solar cell with an open-circuit voltage ( V OC ) of 1.30 volts was prepared, corresponding to 93.5% of the radiative V OC limit and representing the lowest photovoltage loss relative to the theoretical limit observed in WBG perovskites.