Carbon Nanodot Additives Realize High-Performance Air-Stable p-i-n Perovskite Solar Cells Providing Efficiencies of up to 20.2%

Carbonized bamboo-derived carbon nanodots (CNDs) as efficient additives for application in perovskite solar cells (PSCs) are reported. These carboxylic acid- and hydroxyl-rich CNDs interact with the perovskite through hydrogen bonds and, thereby, promote the carriers' lifetimes and realize high-performance p-i-n PSCs having the structure indium tin oxide/NiOx/CH3NH3PbI3 (MAPbI(3))/PC61BM/BCP/Ag. As a result of interactions between the CNDs and the perovskite, the presence of the nonvolatile CND additive increases the power conversion efficiency (PCE) of the PSC from 14.48% +/- 0.39% to 16.47% +/- 0.26%. Furthermore, adding urea, a Lewis base, increases the PCE to 20.2%-the result of a significant increase in the crystal size and a lower content of grain boundary defects and, therefore, longer carrier lifetimes. Cells containing these two additives (without encapsulation) exhibit excellent shelf-life and air-stability, maintaining their high PCEs after storage in air-at a temperature of 25 degrees C and a humidity of 40%-for over 500 h. This performance is among of the best ever reported for p-i-n PSC devices incorporating carbon-based additives.