Interfacial energy-level alignment via poly-3-hexylthiophene-CsPbI3 quantum dots hybrid hole conductor for efficient carbon-based CsPbI2Br solar cells

Abstract

Carbon-based perovskite solar cells (C-PSCs) are promising contenders for the next generation solar cells with high stability and low cost. However, the absence of hole transport layer (HTL) results in a large energy-level mismatch at the interface between perovskite and carbon electrode, which hampers hole extraction and then leads to lower efficiency of C-PSCs compared with metal electrode-based PSCs. In this work, a novel hybrid hole conductor of poly-3-hexylthiophene - CsPbI3 quantum dots (P-QD) is used to improve hole extraction in CsPbI2Br C-PSCs. In this P-QD hybrid hole conductor, P3HT replaces the initial oleic acid ligands around QDs. This not only improves the stability but also facilitates charge extraction and transport of QDs. The application of P-QD in CsPbI2Br C-PSCs effectively improves hole extraction by aligning perovskite/carbon energy-level, thus reducing the non-radiative recombination loss in devices. Furthermore, due to the narrow bandgap, CsPbI3 QDs extend the optical response range of CsPbI2Br solar cells. As a result, the P-QD hybrid hole conductor increases the power conversion efficiency of CsPbI2Br C-PSCs from 13.49% to 15.04%. This strategy provides a new approach for the construction of HTL in C-PSCs.