Enhancing Perovskite Solar Cell Performance via Engineering the Hole Transport Interface with Star-Shaped Nitrogen-Rich Material

Precise perovskite interface modification is regarded as a highly promising strategy to enhance the performance of efficient perovskite solar cells (PSCs). Herein, star-shaped small-molecule interface passivation material (IPM) TB-CZ (N,N',N″-((benzene-1,3,5-triyltris(1H-benzo[d]imidazole-2,1-diyl))tris(benzene-4,1-diyl))tris(9-ethyl-N-(9-ethyl-9H-carbazol-3-yl)-9H-carbazol-3-amine)) was designed and synthesized to regulate the perovskite/spiro-OMeTAD interface. The core of TB-CZ is a nitrogen-rich benzimidazole compound in which the C-N and C═N groups can effectively passivate the Pb²⁺ defects in perovskites through multidentate coordination interactions. The side chain is equipped with a methoxy-free carbazole group, a design that significantly improves the material solubility and thus enhances the quality of perovskite films. The perovskite modified by TB-CZ can effectively optimize its energy levels, promoting hole extraction and transport. Consequently, the TB-CZ-modified PSCs achieve a power conversion efficiency (PCE) of 24.9% at an active area of 0.055 cm² and maintain a commendable PCE of 22.0% even at an upscaled active area of 1 cm², thereby showcasing its outstanding performance. Moreover, the modified device demonstrates remarkable long-term stability by retaining 81% of its initial PCE after storage for 1000 h under ambient conditions without any encapsulation. This work provides a strategy for the rational design of star-shaped passivation materials to enhance the PCE and stability of the PSCs.