Interface engineering by module customization of π-conjugated groups in hole transport materials for perovskite solar cells: Theoretical simulation and experimental characterization

Abstract

Interface engineering is an effective approach to improve the power conversion efficiency (PCE) of perovskite solar cells (PSCs). To achieve the regulation of intermolecular and interfacial interactions from the point of view for the molecular design of hole transport materials (HTMs), the HTMs of CY9 and CY10 are designed by conjugate management on side-chain groups of carbazole-diphenylamine derivatives. Theoretical simulation demonstrates that the larger π-conjugate units in side-chain of CY10 improve the molecular planarity, thereby enhancing the potential for intermolecular π-π stacking and charge coupling. Molecular dynamics (MD) and first-principles simulations indicates that CY10 is uniformly distributed and compactly arranged on perovskite surface, which enhances intermolecular coupling strength, promotes hole transfer, and facilitates the interfacial interactions at perovskites/HTMs interface. The experimental results validated the reliability of the theoretical simulations, which demonstrated that CY10 as HTM exhibited tighter intermolecular π-π stacking, smooth film morphology, low interfacial defect density, and effective suppression of energy loss caused by interfacial non-radiative recombination. Consequently, the PSC devices based on CY10 exhibited a higher VOC than CY9. This work presents a strategy from the point of view for the molecular design of HTMs to enhance the interfacial interactions of the perovskite/HTM interface.