Bending-durable colloidal quantum dot solar cell using a ZnO nanowire array as a three-dimensional electron transport layer

Abstract

The realization of both high efficiency and strong bending-durability is a critical issue for future applications of colloidal quantum dot solar cells (CQDSCs) in flexible devices. Herein, we fabricated flexible CQDSCs with a three-dimensional electron transport layer (ETL) composed of a ZnO nanowire (NW) array for efficient carrier collection and probed the effect of the NW array on the bendability of flexible cells. The good bendability of cells with ZnO NWs was verified from the consistency of photovoltaic performance during mechanical bending treatment with various bending angles and cycles. The efficient release of stress inside the three-dimensional CQDSCs with the ZnO NW array led to the maintenance of 97% of the initial power conversion efficiency at a bending angle of 160°. In contrast, crack formation on the common planar ETL of CQDSCs formed by ZnO nanoparticles resulted in a degradation of device performance to 77% of the initial one at the same angle. Our research demonstrated that the bending stability of the ZnO NW array may be promising for commercial applications of flexible photovoltaic devices.