Dual benefits from “wiring” charge-transfer moieties to perovskite surfaces

Abstract

The unprecedented rates of developments in perovskite photovoltaics have driven seven-fold increase in power-conversion efficiency since 2009. This growth testifies for the broad potential impacts of these materials. While solvent polarity enhances charge separatin (CS) and the rates of charge transfer (CT) leading to CS, the instability of these perovskites in polar environments hurdles the realization of their potentials. Focusing on interfacial CT in nonpolar environment, here we demonstrate the importance of binding a redox-active moiety to cesium tribromoplumbite (CsPbBr3) perovskite nanocrystals (NCs) for achieving efficient CT in hydrocarbon media. Tight-binding compounds, such as amines, etch such low-valency perovskites. Under controlled concentrations, however, binding an amine derivative of a phenothiazine electron donor to NC surfaces not only provides electronic coupling for efficient CT, but also eliminates sites responsible for undesired exciton deactivation. This dual benefit from “wiring” CT mediators to perovskite surfaces ensures efficient charge extraction in nonpolar media, setting key paradigms for interfacing these optoelectronic materials with organic phase.