Hexagonal β-NaYF4:Yb3+, Er3+ Nanoprism-Incorporated Upconverting Layer in Perovskite Solar Cells for Near-Infrared Sunlight Harvesting

Hexagonal β-NaYF4:Yb3+, Er3+ nanoprisms, successfully prepared using a hydrothermal method, were incorporated into CH3NH3PbI3 perovskite solar cells (PSCs) as an upconverting mesoporous layer. Due to their near-infrared (NIR) sunlight harvesting, the PSCs based on the upconverting mesoporous layer exhibited a power conversion efficiency of 16.0%, an increase of 13.7% compared with conventional TiO2 nanoparticle-based PSCs (14.1%). This result suggests that the hexagonal β-NaYF4:Yb3+, Er3+ nanoprisms expand the absorption range of the PSC via upconversion photoluminescence, leading to an enhancement of the photocurrent.