Effects of Electrodeposited Ga-doped ZnO Buffer Layer on the Performance of Inverted Organic Solar Cells

ZnO and Ga-doped ZnO thin films were electrodeposited as buffer layers between an indium tin oxide electrode and a photoactive layer for photo-induced electron transport and photo-induced hole blocking in inverted organic solar cells. Ga-doped ZnO thin films showed improved optical and electrical properties than the bare ZnO thin films, which also affected the performance of OCSs. The device with the Ga-doped ZnO buffer layer presented a higher Jsc value than that with bare ZnO which was caused by the higher transparency and carrier mobility of the deposited buffer layer. However, the Jsc value decreased when the gallium concentration in the films was increased, which induced the larger grain boundary and higher surface roughness and lead to carrier scattering and poor wettability between the buffer layers.