Enhanced charge carrier extraction by a highly ordered wrinkled MgZnO thin film for colloidal quantum dot solar cells

Efficient charge carrier extraction from a colloidal quantum dot (CQD) solid is crucial for high performance of CQD solar cells (CQDSCs). Herein, highly ordered wrinkled MgZnO (MZO) thin films are demonstrated to improve the charge carrier extraction of PbS CQDSCs. The highly ordered wrinkled MZO thin films are prepared using a low-temperature combustion method. The photovoltaic performances of CQDSCs with a combustion-processed MZO (CP-MZO) thin film as an electron transport material (ETM) are compared to those of CQDSCs with a conventional sol-gel processed MZO (SGP-MZO) thin film as an ETM. We performed photoluminescence quenching measurements of the colloidal quantum dot (CQD) solid and charge carrier dynamic analysis of full solar cell devices. The results show that the highly ordered wrinkled CP-MZO thin film significantly increases the charge carrier extraction from the CQD solid and therefore diminishes the charge interfacial recombination at the CQD/ ETM junction, leading to a 15.5% increase in power conversion efficiency. The improved efficiency in the CP-MZO based CQDSC is also attributed to the compact and pin-hole free CP-MZO thin film.