Functionalized Porphyrin as a Carrier Bridge and a Passivator for Perovskite Solar Cells

Abstract

Interfacial modification becomes one of the most emerging strategies in the state-of-the-art perovskite solar cells (PSCs). Here, two porphyrin derivatives (p-MeOTPP, m-DMeOTPP) with different numbers of methoxy groups are employed as the modifiers between perovskite and the hole transporting layer (HTL). The interaction at both of perovskite/modifier and modifier/HTL interfaces, and the hole-transfer property of the modifier itself are comprehensively studied, which are jointly responsible for the significant improvement in the electrical properties of the device. More importantly, discussion on a molecular level reveals the distinct roles of modifiers with highly similar structures. A highest power conversion efficiency (PCE) of 24.56% is achieved for m-DMeOTPP modified PSCs, which is attributed to a synergy of efficient passivation effect at perovskite/modifier interface, sufficient built-in potential at modifier/HTL interface and minimal reorganization energy for hole hopping process. p-MeOTPP has a stronger passivation ability, but causes unfavorable interfacial dipole at modifier/HTL interface and a large energy barrier when hole’s hopping, only resulting in a smaller enhancement in PCE. This work presents a synergy mechanism for interfacial engineering to pursue PSCs with high efficiency and stability, and provides practical guidelines at molecular level to design a modifier not only as an efficient passivator but also as a high-speed carrier bridge.

Keywords: perovskite solar cells, porphyrin derivative, passivation, interface dipole, reorganization energy