Molecular Orientation Regulation of Hole Transport Semicrystalline‐Polymer Enables High‐Performance Carbon‐Electrode Perovskite Solar Cells

Abstract Carbon‐based perovskite solar cells (PSCs) coupled with solution‐processed hole transport layers (HTLs) have shown potential owing to their combination of low cost and high performance. However, the commonly used poly(3‐hexylthiophene) (P3HT) semicrystalline‐polymer HTL dominantly shows edge‐on molecular orientation, in which the alkyl side chains directly contact the perovskite layer, resulting in an electronically poor contact at the perovskite/P3HT interface. The study adopts a synergetic strategy comprising of additive and solvent engineering to transfer the edge‐on molecular orientation of P3HT HTL into 3D molecular orientation. The target P3HT HTL possesses improved charge transport as well as enhanced moisture‐repelling capability. Moreover, energy level alignment between target P3HT HTL and perovskite layer is realized. As a result, the champion devices with small (0.04 cm 2 ) and larger areas (1 cm 2 ) deliver notable efficiencies of 20.55% and 18.32%, respectively, which are among the highest efficiency of carbon‐electrode PSCs.