Cost-Effective Integration of an a-Si: H Solar Cell and a ZnO TFT Ring Oscillator-Toward an Autonomously Powered Circuit

Cost-effective integration of a-Si:H solar cells and oxide-based thin-film transistor (TFT) circuits may lead to broader battery-free device applications. We demonstrate a n-i-p a-Si:H 15-series connected solar cell that supplies power to a ZnO-based ring oscillator. The ring oscillator can operate at 28 kHz at 6 V, corresponding to approximate to 100 mW/cm(2) illumination. This letter describes the integration and compact fabrication of the a-Si:H solar cell and ZnO TFT ring oscillator. The fabrication process includes several mask steps to reduce the number of processing steps.