Minimizing energy losses in perovskite solar cells using plasma-treated transparent conducting layers

• Plasma treatment of FTO glass effectively increases the efficiency of PSCs.
• The surface becomes superhydrophilic after plasma treatment.
• The superhydrophilic surface provides uniform and pinhole-free coverage of TiO2 BL.
• The transmittance of the plasma-treated FTO/BL is higher than the pristine FTO/BL.
• The electron recombination is reduced due to its high quality of TiO2 BL.

This study reports for increasing the efficiency of perovskite solar cells (PSCs) by modifying the surface of a fluorine-doped indium tin oxide (FTO) substrate using an atmospheric pressure plasma treatment. Surface modification of the FTO film involved several challenges, such as control of the blocking layer uniformity, removal of pinholes, and deposition of a dense layer. This strategy allows the suppression of charge recombination at the interface between the FTO substrate and hole conductor. Electrochemical impedance spectroscopy analysis showed that the plasma treatment increased the charge transfer resistance between the FTO and hole conductor from 95.1 to 351.1 Ω, indicating enhanced resistance to the electron back reaction. Analyses of the open-circuit photovoltage decay revealed that modification of the surface of the FTO substrate by plasma treatment increased time constant from 6.44 ms to 13.15 ms. The effect is ascribed to suppression of the electron recombination rate. PSCs based on the newly developed electrode had 39% higher efficiency than reference devices. The obtained results provide direct evidence in favor of the developed strategy.