Analysis of the improved thermal stability of Al-doped ZnO-adopted organic solar cells

The stable performance of organic solar cells (OSCs) at high temperatures is a critical issue for their commercialization. Although a few studies have reported the improved stability of OSCs that adopted Al-doped ZnO (AZO) as an electron transport layer (ETL), systematic research that validates the origins of this improvement has been lacking. In this work, we investigated the underlying mechanism for the improved stability of an OSC with AZO. By adopting AZO, the power conversion efficiency reached 8.65% and retained 70% of its initial value at 85 °C for 6 h, which was an increase in stability of 46% compared to that of an OSC with pristine ZnO. We found that the improved stability of the OSC with AZO originated from the decrease in oxygen defects and the space-charge limited current region through trap-related analyses and the Mott-Gurney law. Therefore, the results supported the enhanced thermal stability of OSCs that incorporated AZO as an ETL.