Overcoming Ni3+‐Induced Non‐Radiative Recombination at Perovskite‐Nickel Oxide Interfaces to Boost Voltages in Perovskite Solar Cells

Nickel oxide (NiOx) is desirable hole selective material (HSMs) for perovskite photovoltaics because of the characteristic in stability and low cost. However, they deliver limited open‐circuit voltage (VOC) compared to some organic HSMs. As it is known, the performance of perovskite solar cells is predominantly limited by trap‐assisted non‐radiative recombination at the perovskite/hole‐selective layer interfaces. A typical lithium‐doping strategy leads to the valence‐band maximum shift and the electronic levels of NiOx can be tuned robustly to match perovskite active layer in perovskite solar cells. More critically, carrier dynamics studies demonstrate another critical PN4N interlayer strategy reduced interfacial density of defect sites and trap‐assisted recombination. These merits contribute coordinately to lower energy loss across the perovskite/NiOx interface and facilitate charge transport process through the relevant interface, yielding VOC values increase to 1.14 V and power conversion efficiencies over 20%. Conjugated polyelectrolyte is inserted between NiOx HTLs and perovskite active layer to reduce interfacial Ni2+ vacancies trap density. This simultaneously passivates trap‐mediated Shockley–Read–Hall recombination and enhances quasi‐Fermi level splitting, yielding an increase in open‐circuit voltage (VOC) values to 1.14 V.