Enhanced Performance and Photostability of Perovskite Solar Cells by Introduction of Fluorescent Carbon Dots

Perovskite solar cells (PSCs) with high efficiency have recently received tremendous attention, but the stability under light irradiation, namely, photostability, of PSCs still represents a major obstacle that must be overcome before their practical applications can be used. The degeneration of perovskite under ultraviolet irradiation from sunlight is a major impacting factor. To solve this problem, in this work we introduce fluorescent carbon dots (CDs), which could effectively convert ultraviolet to blue light in the mesoporous TiO 2 (m-TiO 2 ) layer of the traditional PSCs. As a result, CD-based devices exhibit an improved power conversion efficiency (PCE) of 16.4% on average compared to 14.6% for bare devices, and the light stability of CD-based devices is highly enhanced. These devices can maintain nearly 70% of the initial efficiency after 12 h of full sunlight illumination, while the bare devices maintain only 20% of the initial efficiency. This work indicates that fluorescent down conversion based on CDs is a novel and effective approach to improve the performance and photostability of PSCs.