Tailoring the mercaptan ligands for high performance inverted perovskite solar cells with efficiency exceeding 21%

Interface passivation engineering has been recognized as an effective way to simultaneously contribute to the optoelectronic characteristic and stability of perovskite solar cells (PSCs). Herein, a π-conjugated dual-ligand 1,4-phenylmercaptan (PHMT) is explored to rationally tailor the surface of perovskite film. The experimental and theoretical results show that the PHMT presents planar structure and obvious electron delocalization characteristics, which allow it to anchor on the surface of perovskite with a certain orientation, thereby promoting the transport of interface charge. Moreover, the two sulfhydryl groups in PHMT reduce the trap density of the perovskite film by passivating under-coordinated lead ions. Consequently, the PHMT-modified inverted device based on MAPbI₃ (MA: methylammonium) achieves enhanced efficiency from 18.11% (control) to 21.11%, along with the ambient stability up to 3500 h. After being placed at 85 °C for 500 h or illuminated for 600 h, the modified device remains over 89% or 86% of initial efficiency. This discovery opens a new window for the choice of passivators to improve the performance of PSCs.