Reducing damage of sputtering and improving conductivity of transparent electrodes for efficient semi-transparent perovskite solar cells

Sputtered indium tin oxide (ITO) is widely used as an electrode in semi-transparent and tandem perovskite solar cells. However, damage from sputtering to under layers and the limited conductivity of ITO are still the two main obstacles that hinder further performance improvement of the devices. In this work, the effects and mechanism of sputtering damage and poor conductivity of ITO are investigated based on a traditional perovskite solar cell with bathocuproine (BCP) buffer layer. In order to suppress the sputtering damage, tin oxide (SnO2) is deposited on C-60 to replace the BCP buffer layer. However, it is found that the deposition of SnO2 on the non-reactive C-60 by atomic layer deposition will result in island growth of SnO2 film, which is the key reason for large dark current in solar cells. Fortunately, the phenomenon is inhibited by decorating C-60 surface with WO3 thin film. In order to improve the conductivity of the transparent electrode, an ITO/Au/ITO multilayer architecture is designed. The fill factor (FF) and power conversion efficiency (PCE) of the semi-transparent solar cells (ST-PSCs) with the modified buffer layer and electrodes reached 76.4% and 17.62%, respectively, showing an improvement of FF and PCE when compared to the device with BCP buffer layer and ITO electrode. It is revealed that the optimization also increases the short circuit current of the solar cells. These results provide new strategies for damage reduction of sputtering and performance improvement of ST-PSCs.