Gradient doped nickel oxide hole selective heterocontact and ultrathin passivation for silicon photovoltaics with efficiencies beyond 20%

A prominent feature of photovoltaic devices is their ability to drive photo-generated charges to pathways of asymmetrical conductivity, guiding them to the corresponding electrodes. Under this guideline, the crystalline silicon (c-Si) solar cells dominate the photovoltaic (PV) market for decades and several optoelectronic losses and technological limitations are gradually emerging by now. To circumvent these issues, here, we replaced the doped-silicon emitter layer with a gradient copper-doped nickel oxide (Gd-NiOx), and incorporated a silicon oxide passivation (SOP) layer at the Gd-NiOx/c-Si interface, to construct the novel c-Si PV devices. Interestingly, it was observed that the Gd-NiOx hole selective layer can strengthen the built-in field by minimizing the front electrode/hole-selective layer barrier width and the SOP can reduce interface recombination simultaneously, thereby yielding a remarkable 20.3% efficiency for the proof-of-concept device. We believe the design proposed in this may be of interest for applications in PVs and other optoelectronic devices.