Eclipse Pulsed Laser Deposition for Damage-Free Preparation of Transparent ZnO Electrodes on Top of Organic Solar Cells.

Pulsed laser deposited gallium doped zinc oxide (ZnO:Ga) is reported as transparent top electrode for organic solar cells. In contrast to standard coating techniques, prone to harm organic sublayers and leading to strongly reduced device efficiencies, eclipse pulsed laser deposition (PLD) in argon atmosphere is identified as compatible, nonharmful deposition method for ZnO:Ga, even on top of sensitive organic material. Although PLD is not yet ready for mass production, the experiments reveal and solve crucial process limitations, e.g., droplet impacts, which might be useful also for high yield deposition methods. Optimized ZnO:Ga top electrodes achieve a high mean transparency in the visible spectral range of Tvis = 82.7% and a reasonable sheet resistance of RS = 83 Ω sq−1. The organic photovoltaic devices prepared with this electrode obtained an efficiency of η = 2.9%, almost equal to the efficiency of reference samples using a state-of-the-art metal top contact ( η = 3.0%). The investigations here demonstrate the successful deposition of transparent conductive oxides as top electrode for organic devices and open a new path towards the combination of metal oxides and organic semiconductors. [ABSTRACT FROM AUTHOR]