Constructing Monolithic Perovskite/Organic Tandem Solar Cell with Efficiency of 22.0% via Reduced Open‐Circuit Voltage Loss and Broadened Absorption Spectra

Abstract Combining the high stability under UV light of the wide bandgap (WBG) perovskite solar cells (pero‐SCs) and the broad near‐infrared absorption spectra of the narrow bandgap (NBG) organic solar cells (OSCs), the perovskite/organic tandem solar cells (TSCs) with the WBG pero‐SC as front cell and the NBG OSC as rear cell have attracted attention . However, the photovoltaic performance of the perovskite/organic TSCs needs to be further improved. Herein, nonradiative charge recombination loss is reduced through bulk defect passivation in the WBG pero‐SC front subcell and broadening the range of absorption spectra of the NBG OSC rear cell. For the WBG pero‐SCs, an organic cation chloro‐formamidinium is introduced into FA_0.6MA_0.4Pb(I_0.6Br_0.4)₃ to passivate the bulk defects in the perovskite film and the WBG pero‐SC displays high open‐circuit voltage of 1.25 V and high fill factor of 83.0%. For the NBG OSCs, a new infrared‐absorbing organic small molecule acceptor BTPV‐4Cl‐eC9 is designed and synthesized. Then, a monolithic perovskite/organic TSC is fabricated with the WBG pero‐SC as the front cell and the NBG OSC as the rear cell, and the TSC demonstrates high power conversion efficiency up to 22.0%. The results indicate that the perovskite/organic TSC is promising for future commercialization.