Unravel the Charge-Carrier Dynamics in Simple Dimethyl Oxalate-Treated Perovskite Solar Cells with Efficiency Exceeding 22%

Understanding the effect of additive on the interfacial charge-carrier transfer dynamics is very crucial to obtaining highly efficient perovskite solar cells(PSCs).Herein,we designed a simple additive,dimethyl oxalate(DO),functioning as an effective defect passivator of perovskite grain boundaries via the coordination interaction between the carbonyl(C=O)and the exposed Pb^(2+).The modification with DO produces pinhole-free and compact perovskite films,enhancing the transportation capability of carriers.As a consequence,the DO-treated PSCs exhibited a power conversion efficiency(PCE)of 22.19%,which is significantly higher than that of the control device without additive(19.58%).More importantly,detailed transient absorption characterization reveals that the use of additive can decrease the hot-carrier cooling dynamics,improve the carrier transfer,and eliminate nonradiative recombination in PSCs.This present work provides a profound understanding the additives effect on the carrier dynamics in PSCs toward the Shockley-Queisser limit.