Control Perovskite Crystals Vertical Growth for Obtaining High‐Performance Monolithic Perovskite/Silicon Heterojunction Tandem Solar Cells with VOC of 1.93 V

The efficiency of perovskite (PVK)/silicon tandem solar cells have the potential to beyond the Shockley–Queisser limit of single‐junction solar cell and the theoretical efficiency can reach over 35%. Improving the quality of PVK film can reduce nonradiative charge recombination. Herein, MACl is added to the PVK precursor, compared with the control cell, adding MACl can assist the vertical crystallization of PVK film, accelerates carrier vertical transport, reduces bulk defects in the active layer. Moreover, MACl can upshift the valence band energy level, making it better band alignment with hole‐transport layer. As a result, the fill factor (FF) and open‐circuit voltage (VOC) are improved with MACl addition. The champion MACl‐added PVK solar cell with 1.67 eV bandgap achieves an efficiency of 18.94% and a VOC of 1.225 V. Using the optimized wide bandgap PVK solar cells to fabricate the rear‐textured monolithic PVK /silicon heterojunction tandem solar cells, a champion efficiency of 24.16% and a VOC of 1.93 V are obtained. It is demonstrated that the control of PVK crystals vertical orientation provides an effective strategy for improving the efficiency of PVK‐based solar cells.