Nickel compound quantum dots as inorganic hole transporting layer in perovskite solar cells

Nickel oxide has grabbed the attention as one the most efficient materials for inorganic hole transporting layer in perovskite solar cells. However, it is quite a challenge to control the growth conditions of NiO film. In this work, the nickel compound quantum dots prepared via the electrochemical process are investigated as HTL for the PSCs. From absorbance spectra, the mixed phase of NiCl2 and NiOOH are observed. The average size of nickel compound quantum dots is about 2–4 nm from transmission electron microscopy. The solutions of nickel compound quantum dots are used to fabricate the PSCs with a p-i-n structure consisting of Fluorine doped Tin Oxide glass/nickel compound quantum dot/perovskite/PCBM/Ag. It is found that the NiO films prepared from nickel compound quantum dots show the full covered film, resulting in higher power conversion efficiency of 12.47% as compared to that of the reference NiCl2. The improvement in efficiency can be explained by increasing short circuit current density and fill factor. In addition, the stability of PSC based on nickel compound quantum dots demonstrates higher stability than the other condition. Thus, PSCs based on nickel compound quantum dots can be used to improve the interface of HTL and perovskite layer in PSC and result in the enhancement of the PSC performance.