Synergetic effect of organic metal compound modified SnO2 in high performance perovskite solar cells

Abstract

The various imperfections in electron transport layer (ETL), perovskite absorber and their interfaces greatly damage the efficiency, hysteresis and stability of perovskite solar cells (PSCs). Herein, we present a simultaneous defect passivation method by a novel hydrophilic organic salt, ethylene diamine tetra acetic acid disodium magnesium (EDTADM), to realize the efficient modulation of ETL, perovskite film and their interfaces. Pure SnO2 ETLs were formed by SnO2 aqueous colloidal dispersion. A trace amount of EDTADM was deposited onto SnO2 ETLs. The carboxyl and trialkylamine functionality and Mg2+/Na + cations of in EDTADM additive cause reduced defective and highly conductive SnO2 ETLs, which offers distinguished platforms for the growth of perovskite layers with high-quality crystallinity and compact morphologies to promote the interfacial charge transfer. The incorporation of EDTADM leads to the notable passivation through establishing coordination interactions with Sn4+ or Pb2+ in SnO2 and perovskite films. Moreover, Mg2+/Na+ cations of the additive can partly get into the absorber through heat diffusion to further suppress the imperfection states, boosting the photovoltaic performance of the PSC devices. Such simultaneous optimization for SnO2 ETLs, perovskites and their interface allows the fulfillment of high power conversion efficiency (PCE) of 20.81 % with decreased hysteresis and enhanced stability for EDTADM - containing PSCs. Unsealed PSCs with EDTADM displays better ambient stability. They maintain 68 % of their original PCE after being stored under ambient condition (25–30 °C, 50–65% relative humidity) for 1300 h, while the PCE of the reference devices degrades to 28 % after the aging.