Amino-rich carbon quantum dots decorated SnO2 ETL with enhanced charge extraction for efficient perovskite solar cells

Abstract

An electron transport layer (ETL) with excellent conductivity and charge extraction ability plays a vital role in accelerating charge extraction and transportation for achieving highly efficient planar perovskite solar cells (PSCs). Herein, amino-rich carbon quantum dots (shortened as ACDs hereafter) with multi-roles are developed and introduced into SnO2 precursor solution to enhance the photoelectric properties of SnO2. First, the conductivity and the Fermi energy level of SnO2 are improved via electron injection from ACDs. With the help of ACDs, the conductivity of SnO2:ACDs is increased from 2.77 × 10−2 mS/cm2 to 6.56 × 10−2 mS/cm2 under illumination, which contribute to efficient charge transport and collection within PSC device. Secondly, the amino functional groups on the surface of ACDs promote the saturated growth of perovskite grain, forming high-quality photoactive layers. When deposited on the SnO2:ACDs, the average gain size of perovskite film is increased from 0.86 μm to 1.1 μm. These outstanding properties greatly accelerate the charge extraction and reduce the trap density within the perovskite layer. As a result, the PSC with ACDs exhibit a champion efficiency of 22.02 % compared with 20.33 % of the control device, and the device stability is also significantly improved.