Impact of the bilayer electron transport layer in the donor acceptor bulk heterojunctions for improved inverted organic photovoltaic performance

•Fabrication of inverted-geometry organic solar cells on glass substrates, focusing on the impact of inorganic-organic interface region on molecular morphology in the organic active layer and overall device performance.•Determination of crystallinity in the top layers of TiO2/ZnO thin films using synchrotron-based, thickness-dependent, multiple angle grazing incident wide-angle X-ray scattering (GIWAXS).•Optimisation of the interfacial molecular order of the conjugated polymer (PTB7-Th) and non-fullerene acceptor (IEICO-4F) in the bulk heterojunction of the photovoltaic active layer over TiO2/ZnO electron transport layers in an inverted device architecture.•An increase of more than 31% in the power conversion efficiency of photovoltaic devices by indirect control of the optimal phase segregation of the donor:acceptor pairs in the organic active layer, as evidenced by TOF-SIMS analysis.