High Photovoltage Inverted Planar Heterojunction Perovskite Solar Cells with All-Inorganic Selective Contact Layers

Inverted planar heterojunction perovskite solar cells based on all-inorganic selective contact layers show great promise for commercialization owing to their competitiveness in terms of cost and stability. However, the power conversion efficiencies (PCEs) of the few reported perovskite solar cells with this type of device structure have been limited by relatively low photovoltages. Here, we propose a new device structure comprising electron beam-evaporated nickel and niobium oxides as the hole and electron selective contact layers, respectively. We demonstrate that a metal oxide material can be directly deposited on a perovskite film by electron beam evaporation without damaging the interface. We propose that the turn-on voltage of the p-n junction formed by the selective contacts represents a quantitative proxy of the charge blocking performance. A high turn-on voltage of 1.36 V is obtained for the NiO_x/Nb₂O₅ p-n junction. An open-circuit voltage of 1.16 V is achieved using a hybrid organic-inorganic perovskite with a band gap of 1.6 eV. The large photovoltage, enabled by the excellent charge extraction and blocking properties of the inorganic selective contact layers, leads to the highest PCE of over 19.0% for this class of device.