Gallium-doped zinc oxide films as transparent electrodes for organic solar cell applications

Abstract

We report microstructural characteristics and properties of gallium-doped ZnO films deposited on glass by pulsed laser deposition. The ${\text{Zn}}_{0.95}{\text{Ga}}_{0.05}\text{O}$ film deposited at $200°\text{C}$ and $1\times {10}^{-3}\text{Torr}$ showed predominant $⟨0001⟩$ orientation with a metallic behavior and a resistivity of $2\times {10}^{-4}\Omega \text{cm}$ at room temperature. Low resistivity of the ZnGaO films has been explained in terms of optimal combination of carrier concentration and minimized scattering, and is correlated with the microstructure and the deposition parameters. Power conversion efficiency comparable to indium tin oxide-based devices $\left(1.25\pm 0.05\%\right)$ is achieved on a ${\text{Zn}}_{0.95}{\text{Ga}}_{0.05}\text{O}∕\text{Cu-phthalocyanine}∕{\text{C}}_{60}$ double-heterojunction solar cell.