Nickel-oxide hole-transport layers prevent abrupt reverse-bias breakdown and permanent shorting of perovskite solar cells caused by pinhole defects

Abstract

When perovskite solar cells (PSCs) are subjected to reverse bias, they often abruptly pass large current densities through localized film defects. The large, localized current induces heating that quickly and permanently damages the materials in the device – including transport layers, perovskite, and metal contacts – and often leads to permanent electrical shorting of the device. We employed a 30-nm-thick nickel oxide (NiO_X) hole transport layer (HTL) in PSCs and found that NiO_X decreased the likelihood that cells show abrupt reverse-bias breakdown and prevented permanent shorting and severe thermal damage. We found that cells using NiO_X could recover up to 84% of their initial PCE even after passing −20 mA cm⁻² of average reverse current densities (the cell's one-sun short-circuit current density) for 5 minutes. Cells with all-organic HTLs were permanently shorted afterwards. In addition to preventing abrupt breakdown, photoluminescence images of cells before and after reverse-bias breakdown show that NiO_X also prevents localized damage to the perovskite and transport layers, presumably due to its superior uniformity and thermal stability compared to organic HTLs.