Indium doped ZnO thin films prepared by sol-gel technique for efficient inverted type of polymer solar cells

We demonstrate indium doped ZnO (IZO) thin films used as electron transport layers (ETLs) for P3HT:PCBM bulk heterojunction (BHJ) polymer solar cells. The IZO thin films were deposited by a low-temperature sol-gel method and their electric and optical properties regarding different indium contents were discussed for improving electron transport. The results show significantly higher fill factor for the devices based on the IZO thin films compared to the pure ZnO thin films, leading to remarkable improvement for power conversion efficiency. For the best cells, the conversion efficiency at AM1.5G illumination was 4.18%. The flexible cells using IZO ETLs were also fabricated for both highly stable and efficient flexible photovoltaic applications.