ITO/Ag/ITO and ITO/Cu/ITO transparent rear contacts for semi-transparent perovskite solar cells

The indium tin oxide (ITO) film is usually deposited as the conductive and transparent contact for semi-transparent perovskite solar cells (ST-PSCs). It is challenging to prepare high quality ITO layer at low processing temperature below 50 °C. In this research, a sandwiched structure of ITO/Ag/ITO and ITO/Cu/ITO deposited at room temperature by sputtering is proposed as the transparent rear contact for ST-PSCs. It is shown that by adjusting the surface morphology and thickness of the metal interlayer, the average visible transmittance (wavelength range of 380–780 nm) can be improved to 92.6%, and the sheet resistance is lower than 15.0 Ω/□. By taking advantage of the good opto-electrical properties, both short circuit current density and fill factor of ST-PSCs with IAI and ICI rear contacts can be improved by about 1.0 mA/cm2 and 10%, respectively. The cell conversion effeciency of ST-PSCs can be maintained above 13.0% even with the perovskite layer thickness reduced to 488 nm. The cell conversion efficiencies of about 15.8% and 9.0% were obtained for a ST-PSC as illuminated from the glass substrate and IAI rear contact, respectively.