Surface Planarization and Chemical Adhesion Enable 25.0% Efficient Perovskite Single-Crystal Solar Cells

Polycrystalline perovskite solar cells (PSCs) have achieved record efficiencies through facile passivation strategies during crystallization. By contrast, single-crystal PSCs face unique challenges. Their growth requires pristine, additive-free conditions, and controlling facet passivation remains difficult both during and after crystallization. These limitations primarily manifest as higher trap density at interfaces with charge-transport layers rather than within the crystal bulk. To address this challenge in single-crystal PSCs, we modified the hole-transport layer (HTL) surface by using a hydrophilic dielectric polymer. This treatment prevents charge leakage near pinholes while maintaining the single crystal adhesion. Our champion device achieved a high fill factor of 0.82, a large V_oc of 1.08 V, and a record-setting power-conversion efficiency of 25.0% for single-crystal PSCs. Furthermore, the polymer’s hydrophilic properties, combined with strong crystal adhesion, enhanced the device’s operational stability. This work advances single-crystal PSC technology by addressing critical interfacial engineering challenges through a strategic HTL surface modification.