Interfacial dipole engineering by self-assembled molecules in n-i-p and p-i-n perovskite solar cells.

Self-assembled molecules are widely used as bottom interfacial layers in inverted perovskite solar cells, yet their application to perovskite top surfaces remains poorly understood. Here, we develop two self-assembled molecules for perovskite surface modification and interfacial optimization with the hole transport layer. Through solvent engineering, ordered and uniform molecular packing is achieved on the perovskite surface. These molecules optimize surface energetics and promote efficient hole transfer when coupled with a homologous hole transport layer. Their large molecular dipoles tune interfacial energy alignment and reduce energetic offsets, thereby accelerating charge extraction from the perovskite layer. This dipole-driven interfacial modulation is effective in both normal and inverted device architectures. As a result, a power conversion efficiency of 26.18% (certified 26.23%) is achieved in normal-structure devices, together with improved operational stability under maximum power point tracking. This work establishes a viable strategy for perovskite surface engineering using self-assembled molecules.