Perovskite/Organic Tandem Solar Cells with 26.49% Efficiency via Enhanced Absorption and Minimized Energy Losses.

Although perovskite/organic tandem solar cells have many advantages, their power conversion efficiency (PCE) still substantially lags behind their perovskite/perovskite counterparts. One of the main reasons is the low external quantum efficiency and high energy loss of the rear subcell. In this work, guided by the semi-empirical analysis, the most suitable available material combination has been obtained. To further improve the photovoltaic performance of the organic rear cells, isopropanol has been used as a co-solvent additive to finely tune the bulk heterojunction morphology of the active layer. Together with the optimization of each subcell, a remarkable PCE of 26.49% (certified 25.56%) with a high open-circuit voltage of 2.214 V has been achieved for the perovskite/organic tandem device.