Numerical simulations of PbS colloidal quantum dots solar cell with ZnO: PEIE-based electron transport layer

Electron transport layers (ETLs) that could be processed at low temperatures are always preferred for the application in heterojunction thin films solar cells. The low temperature processed flexible transport layers have two fold advantages in fabricating flexible devices with high durability and lower probability of temperature-related degradation. In the past, researchers utilized the zinc oxide: polyethyleimine ethoxylated (ZnO: PEIE) composite-based electrons transport layer in flexible polymer solar cells due to its unique properties in terms of low-temperature processability, mechanical flexibility, and potential to modulate the ZnO work function and many more. However, its application in colloidal quantum dots (CQDs) solar cells has not been investigated in the past. Therefore, to extend the horizon of this material to PbS CQDs solar cell, we have reported a PbS CQDs solar cell having ZnO: PEIE-based ETL. The device under consideration is carefully designed and investigated with ZnO: PEIE-based ETL with different PEIE concentrations ranging from 0.05% to 0.3%. Fundamentally, the work function of ZnO: PEIE reduces with an increase in the concentration of ZnO: PEIE. It has been obtained through numerical simulations that the reduced work function of ZnO: PEIE improves the band alignment with the absorber layer and hence increases the photovoltaic parameters. The results showed that PEIE concentration at 0.3% reduced the interfacial resistance and improved the conversion efficiency to 10.4%. The work reported in this study may open the window for developing ZnO: PEIE ETL-based flexible PbS CQDs solar cells with high efficiency in future.