The influence of top electrode work function on the performance of methylammonium lead iodide based perovskite solar cells having various electron transport layers

Perovskite solar cells (PSCs) have received much attention due to their low manufacturing cost and high conversion efficiency. Charge transport layer present in PSC helps extract photo-generated charge carriers. Although abundant research has been done in finding suitable charge transport layers, there are still many scopes to study the different charge transport layers. This work presents a theoretical study of PSCs with five different electron transport layers (ETLs) used independently and also as stack while also varying the top electrode (cathode) work function to determine its influence on the overall performance of PSCs with different ETLs. Our result shows stacked TiO₂/PCBM ETL devices are more resistant structure to variations in the cathode work function. J_sc is independent of electrode work function for all ETLs. V_oc remains unaffected for almost all ETLs until the electrode work function of 4.8 eV. Fill factor and conversion efficiency depends on ETL and electrode work function. As the cathode work function is increased, at the FTO/ETL interface, electric field initially pointing from FTO to ETL is gradually changing and pointing from ETL to FTO. The former favours electron transport and the latter un-favour electron transport from ETL to FTO. Therefore, fill factor and efficiency decreased as the work function is increased. Devices with TiO₂, SnO₂, ZnO, WO₃, and SrTiO₃ yielded maximum efficiencies of about 26%, 27.5%, 27.5%, 27%, and 27%, respectively. Our result shows electric field at the FTO/ETL interface and cathode work function determines the device performance. This work provides new insights into PSC and paves way for improving performance.