Ladder-like conjugated polymers used as hole-transporting materials for high-efficiency perovskite solar cells

Abstract

The intramolecular S–O interaction was first adopted for designing conjugated polymer HTMs in perovskites solar cells. It could lock the flat conformation of polymer backbones, which enabled the polymer molecules to pack closely in the solid state, facilitating hole transportation. The solubility of the conjugated polymers could be improved by introducing alkyloxy side chains, whereas their planarity in the solid state was not affected. Furthermore, high hole mobility of 1.72 × 10⁻³ cm² V⁻¹ s⁻¹ and a suitable HOMO energy level of −5.43 eV could be achieved by side chain engineering. Finally, PCE of 18.30% was obtained for P1-based dopant-free devices, which most importantly showed much better long-term ambient stability than those based on traditional spiro-MeOTAD.