Efficient polymer solar cells with low-temperature thermal annealing and ultraviolet-ozone treatment solution-processible NiO films as ITO-modified films

Nickel oxide (NiO) is a commonly used material for the hole extraction layer (HEL) in polymer solar cells (PSCs). In this study, we prepared NiO films by spin coating a NiO nanoparticle solution on an ITO surface and then subjected the NiO films to low-temperature thermal annealing (90 °C) and ultraviolet ozone (UVO) treatment to form NiO films (SU-NiO). Compared with E-NiO films (vacuum-evaporated NiO powder), SU-NiO has a similar resistivity and electrical conductivity, and the hole transport capability of the SU-NiO films is greater than that of the PEDOT:PSS reference films. The photovoltaic performance of the SU-NiO-based PSCs is comparable to that of the E-NiO-based PSCs and slightly greater than that of the PEDOT:PSS-based reference PSCs. Therefore, SU-NiO-based PSCs have the advantage of solution processability method, low-temperature thermal annealing treatment and isn’t obviously sacrifice photovoltaic performance compared to E-NiO-based PSCs. These results indicate that SU-NiO films are promising HEL materials for the practical fabrication of PSCs.