Graphene/ZnO nanocomposite as an electron transport layer for perovskite solar cells; the effect of graphene concentration on photovoltaic performance

Perovskite solar cells (PSCs) have been fabricated by a graphene/ZnO nanocomposite (G/ZnO NC) as an electron transporting layer. We use a novel spray deposition method compatible with large area processing methods for deposition of pristine ZnO and G/ZnO NC films. We show the effect of varying the graphene concentration in the G/ZnO NC films from 0 to 1 wt% on the photovoltaic performance of PSCs. We find that a 0.75 wt% graphene concentration in the G/ZnO NC films gives an optimum PSC performance with short circuit current density and power conversion efficiencies going up from 15.54 to 19.97 mA cm(-2), and 7.01 to 10.34% respectively as compared to pristine ZnO. The enhancement in photovoltaic performance is attributed to the superior growth of the perovskite thin-film and enhanced electron transport/extraction on using the graphene network in the NC.