A Scorpion–Type Dopant‐Free Hole Transport Material for n‐i‐p Organic–Inorganic Hybrid Perovskite Solar Cells

Abstract It is significant to develop dopant‐free hole transport materials (HTMs) to improve the long‐term stability of n‐i‐p organic–inorganic hybrid perovskite solar cells (PSCs). In this work, two HTMs (DTTP‐T and DTTP‐D) based on dithienothiopyrrole (DTTP) core were synthesized to explore the effects of different substituents on the nitrogen atom on the properties of HTMs. Compared with anisole‐substituted DTTP‐D, triarylamine‐substituted scorpion‐type DTTP‐T shows better matching energy level, stronger charge transfer and defect passivation ability. Therefore, the power conversion efficiency (PCE) of dopant‐free DTTP‐T‐based n‐i‐p PSCs reaches 18.67 %, which is comparable to that of doped Spiro‐OMeTAD (19.51 %). More encouragingly, the efficiency of DTTP‐T‐based devices remains above 80 % of its initial efficiency after 1728 h of storage in air, while the Spiro‐OMeTAD‐based devices could only maintain 600 h. This work provides a good reference for the development of dopant‐free small molecular HTMs for efficient and stable PSCs.