Use of AuCl ₃ -doped graphene as a protecting layer for enhancing the stabilities of inverted perovskite solar cells

Relatively-low long-term stabilities of perovskite solar cells (PSCs) despite the excellent photovoltaic properties are a critical obstacle to their practical applications. A stack of poly(3,4-ethyle nedioxy thiophene):poly(styrenesulfonate) (PEDOT:PSS)/indium tin oxide (ITO) is widely used as a key element in p-i-n perovskite PSC structures, but is also one of the major sources for degrading the performance of the PSCs, mostly resulting from the high acidity of PEDOT:PSS. Here, we first employ gold(III) chloride (AuCl ₃ )-doped graphene (GR) as a protecting layer between PEDOT:PSS and ITO for improving the efficiency and durability of the PSCs. The AuCl ₃ -GR PSC shows maximum power conversion efficiencies (PCEs) of 15.77/15.90% for forward/reverse condition at a AuCl ₃ concentration of 10 mM, much larger than those (14.16/14.21%) of the PSC without GR. After 30 days under ambient condition, the former PSC retains 67% of its original PCE with the operation of the latter PSC being stopped. The enhancement of the PCE and the stability result from the improvement in the protection of ITO as well as in the collection of holes by the inclusion of the AuCl ₃ -GR.