Fused Dithienopicenocarbazole Enabling High Mobility Dopant-Free Hole-Transporting Polymers for Efficient and Stable Perovskite Solar Cells

As a critical component in perovskite solar cells (PSCs), hole-transporting materials (HTMs) have been extensively explored. To develop efficient dopant-free HTMs for PSCs, a decent hole mobility (>10–3 cm2 V–1 s–1) is critically essential, which is, however, seldom reported. In this work, we introduce two novel donor–acceptor (D–A) type conjugated polymers (PDTPC-1 and PDTPC-2) with narrow bandgap unit, i.e., fused dithienopicenocarbazole (DTPC), as the donor building block and benzo[c][1,2,5]thiadiazole derivatives as the acceptors. The highly planar and strong electron-donating DTPC endows the polymers with superior hole mobility up to ∼4 × 10–3 cm2 V–1 s–1. Because of the better energy alignment with perovskite and excellent film-forming property, PSCs with PDTPC-1 as HTM show an appreciably enhanced PCE of ∼17% in dopant-free PSCs along with improved device stability as opposed to PDTPC-2. Our work revealed for the first time that the introduction of narrow bandgap DTPC in D–A polymers could achieve remarkably high hole mobility in the pristine form, favoring the application in dopant-free PSCs.