Improving the power conversion efficiency of perovskite solar cells by adding carbon quantum dots

High-quality perovskite films are the key factor in manufacturing high-performance devices. In this work, we for the first time use carbon quantum dots (CQDs) as additive in the methylammonium iodide solution for high-quality CH3NH3PbI3 (MAPbI(3)) films. Appropriate concentration of CQDs (0.04 mg ml(-1)) can passivate the crystal defects, improve the crystallinity, increase the grain size and reduce the grain boundary of MAPbI(3) film. Various characterization results show that CQDs additive can reduce trap-state density, decrease carrier recombination and improve photoelectric performance. Compared with the pristine device, the average power conversion efficiency (PCE) of CQD-modified MAPbI(3) device was increased from 15.8 +/- 0.37% to 18.81 +/- 0.45%, and the maximum PCE of champion device was increased from 16.21 to 19.17%. In this study, we propose a simple method for the preparation of stable and efficient inverted planar structure perovskite solar cells using CQD additives in a two-step spin-coated deposition method.