Efficient and Stable Perovskite Solar Cells based on Nitrogen-Doped Carbon Nanodots.

The role of graphitic and amorphous nitrogen-doped carbon dots (N-CDs) as additives for perovskite solar cells (PSCs) is investigated. A detailed study of N-CDs: perovskite (PVSK) blends through X-ray diffraction, nuclear magnetic resonance, field emission scanning electron microscopy, UV-vis, and photoluminescence spectroscopy reveals the existence of interactions between N-CDs and PVSK. The amorphous or graphitic nature of these carbon nanoforms, as well as the interactions between CDs and PVSK, clearly determines the photovoltaic outcome of the PSCs. Thus, a small amount of graphitic carbon dots (g-N-CDs) leads to more-stable PSCs, while maintaining and even improving the power conversion efficiency (PCE). In addition, the long-term evaluation of the g-N-CDs-containing cells shows improvement of the PCE over time, up to 109% of the initial efficiency after 40 days while the reference performance is dropped to 86%.