Electrical degradation and recovery of NiO/ZnO visible-light-transparent flexible solar cells

Fundamental photovoltaic parameters such as current density–voltage characteristics of flexible NiO/ZnO solar cells were investigated; the study revealed the degradation and recovery properties of the cells. The open-circuit voltage and shunt resistance of the flexible NiO/ZnO solar cells tended to decrease subsequent to bending; however, the short-circuit current and series resistance remained constant. This indicated that the number of defects caused by bending tend to increase proximate to the NiO/ZnO interface as compared to that of the bulk of the flexible solar cell. Moreover, the decreased solar cell performance caused by bending improved through heat treatment at 150 °C for 15 min. The results obtained could serve as the first step towards the realization of flexible visible-light-transparent solar cells using polycrystalline films.