Highly-dispersible reduced graphene oxide/polymer nanocomposites as efficient hole-transporting materials for perovskite solar cells

In this research, we demonstrate that a solution-processable reduced graphene oxide/poly (N-vinylpyrrolidone) nanocomposite (rGO/PVP) can be easily obtained by a scalable and cost-effective electron beam-based method; and further, that it functioned well as a hole-transport layer (HTL) in perovskite solar cells (PeSCs). The rGO/PVP composites were produced by electron-beam irradiation-induced reduction of GO/PVP mixtures in ethanol/distilled water (50 v/v %), without any heat or reducing agents. The prepared rGO/PVP showed dispersion stability of six months, even in an aqueous alcoholic solvent of 5 mg/mL. Its solution-processed thin film demonstrated a uniform, smooth surface, and full-cover morphology, a good conductivity of ~0.2 S/cm, and a high work function of 5.15 eV. As a result, the solution-processed rGO/PVP as HTL for the PeSCs outweighed the conventional graphene nanoflakes (GNFs), producing higher device efficiency. Worthy of note, the rGO/PVP-based PeSCs showed better power conversion efficiency (PCE) and device stability than the reference poly (3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS)-based counterpart. This finding demonstrates that the rGO/PVP composite, which is easily producible via cost-effective and large-scale affordable electron beam technology, could provide a promising solution-processable GNFs-based HTL for long-lasting high-performance PeSCs.