Promising ITO-free perovskite solar cells with WO3-Ag-SnO2 as transparent conductive oxide

Among various kinds of materials to substitute indium-tin-oxide (ITO) in rigid or flexible solar cells, oxide-metal-oxide (OMO) is one of the most promising. In this work, by means of reactive plasma deposition, a new combination of OMO structures, WO3/Ag/SnO2 (WAS), was deposited in one pot and each film thickness optimized to obtain high transmittance from 400 nm to 850 nm in wavelength and low sheet resistance, as well as mechanical robustness. The typical perovskite solar cells (PSCs) based on bare WAS composite film show poor device performance. Hence, aqueous soluble SnO2 nanoparticles were applied to modulate the band level mismatch at the interface between the WAS and MAPbI(3) layers and the best-performing device with 14% conversion efficiency was achieved, which is the highest value reported hitherto with OMO structures as transparent conductive electrodes in PSCs. The results from various characterizations verify the interface engineering effect of the SnO2 nanoparticles. The unencapsulated WAS-based device stability also is comparable to that of the ITO-based device in continuous light exposure in ambient atmosphere (37% RH and 60 degrees C). This work reveals a great potential of OMO in place of ITO in solar cells while it still needs more attention and efforts in continuing development.