Metal halide perovskite-containing multijunction photovoltaics

Thanks to their superior bandgap tunability and high absorption coefficient, metal halide perovskites demonstrate high potential for fabricating multijunction photovoltaics capable of achieving power conversion efficiencies surpassing the radiative efficiency limit of single-junction solar cells[1],[2]. One of the key challenges currently facing all-perovskite multijunction photovoltaics is the low quality of the narrow bandgap (~1.25 eV) mixed tin-lead perovskite films used as the rear absorber. At this conference, we will present our recent investigations on the mixed tin−lead perovskites covering the control of the Sn(II) oxidation[3], interface carrier extraction[4], and in-situ surface reaction[5], as well as the understanding of the solution chemistry and resultant crystallization[6], aiming to generate a global picture toward the comprehensive understanding of this material and its photovoltaic devices. As a result, we have obtained efficiencies of over 23.9% for the single-junction tin−lead perovskite devices, with an open circuit voltage of up to 0.91 V. Building on optimizations of neat lead perovskites, we then showcase the successful integration of these improved mixed tin-lead perovskites into double-, triple-, and quadruple-junction tandem solar cells, achieving efficiencies exceeding 29%, 28%, and 27%, respectively. In addition, we will propose promising strategies for enhancing the light and temperature stability of the involved perovskite subcells, aiming to improve the reliability of efficient all-perovskite multijunction photovoltaics. Furthermore, we will also share insights and recent progress achieved in perovskite-on-silicon multijunction cells.