Dual- and triple- hetero-atom-doped carbon dots as novel additives for the engineering of defects passivation to boost performance of perovskite solar cells

Abstract

Methylammonium lead iodide (MAPbI3)-based perovskite solar cells (PSCs) offer highly efficient photovoltaics. However, several disadvantages such as poor stability and possibility of defect formation reducing film quality have restricted its commercialization. In this work, we reported the synthesis of dual- and triple-hetero-atom-doped carbon quantum dots (CQDs) via hydrothermal method and their effect of use as additive on the performance of PSCs. The boron (B) and phosphorous (P)-doped CQDs (B,P-CQDs), sulphur (S) and P-doped CQDs (S,P-CQDs), and B, S, and P-doped CQDs (B,S,P-CQDs) additives were described. Since these CQDs have many functional groups including hydroxyl (-OH), they can easily interact with Pb ions leading to the formation of PbO, as well as interaction with methyl ammonium ions. A reduced halide vacancy density and an increased nucleation energy of perovskite enhance crystal sizes and charge transfer. The passivation of surface defects reduces non-radiative recombination and ion migration, which plays an important role in photodegradation of the MAPbI3 films. Herein, the introduction of S,P-CQDs improved power conversion efficiency (PCE) from 10 to 15% and current density (Jsc) from 14.4 to 23.6 mA cm-2. PSCs added with dual- and triple-hetero-atom-doped CQDs showed narrower efficiency distribution in comparison to the control devices.