Efficient planar heterojunction perovskite solar cells employing a solution-processed Zn-doped NiOX hole transport layer

Optimal interface of planar heterojunction perovskite solar cells determines efficient charge transport and collection for achieving high power conversion efficiency. Nickel oxide (NiOX) is one of the most well-known hole transport materials for perovskite solar cells because of its wide band gap, p-type transport characteristic, good chemical stability and high optical transparency. However, pristine NiOX possesses unsatisfactory electrical properties such as high surface trap density or low electrical conductivity which could deteriorate the device performance. We thus adopted Zn as a dopant to employ the Zn-doped NiOX as a hole transport layer in the planar heterojunction PSCs as considering that not only Zn has a similar atomic size with Ni but also Zn forms highly crystalline oxide materials. As a result, 5% Zn-doped devices achieved a power conversion efficiency up to 13.72% with improvements of a VOC by 4.0%, a JSC by 16.7% and a fill factor by 8.9% as compared to the un-doped NiOX counterpart.