Comparison of NiOx thin film deposited by spin-coating or thermal evaporation for application as a hole transport layer of perovskite solar cells

We compared nickel oxide (NiOx) deposited by thermal evaporation and that deposited by the spin-coating process, for use in the hole transport layers of inverted planar perovskite solar cells (PSCs). Spin-coating deposition for NiOx HTL has been widely used, owing to its simplicity, low cost, and high efficiency. However, the spin-coating process has a technical limit to depositing a large-area uniformly. In contrast, thermal evaporation fabrication has a low price and is able to produce uniform and reproducible thin film. Hence, the chemical states, energy band alignment, surface morphologies, and microstructures of NiOx deposited by spin coating and thermal evaporation were analyzed. The PSC with NiOx HTL deposited by thermal evaporation showed a higher power conversion efficiency of 16.64% with open circuit voltage 1.07 V, short circuit current density of 20.68 mA cm−2, and a fill factor of 75.51% compared to that of PSC with spin-coated NiOx. We confirmed that thermal evaporation can deposit NiOx to give a better performance as a HTL with higher reproducibility than spin-coating.