Fabrication of ITO/FTO Free Flexible Solar Cells Based on ZnO Nanostructures on the Polyethylene Terephthalate/Al/Ti Substrate

Here in, inverted structured bipolar heterojunction solar cell was fabricated on ITO-free flexible polymer (PET) substrate. A transparent and conducting polymer substrate in combination with nanostructures layers on the substrate was prepared using photoetching, and barrier layer of Al and metal layer of Ti were deposited on the photoetched surface using e-beam evaporation technique. Structural, morphological and electrical properties of the PET substrate and the deposited layers were studied by using various characterization techniques including XRD, FESEM, AFM, and electrical measurements. ZnO nanorods structure were grown on the Al/Ti deposited layer on PET substrate and XRD results confirm the formation of hexagonal wurtzite structure of ZnO on the top of Al/Ti layer with good crystallinity. Morphological properties studied by using FESEM reveal the rod shape morphology of the ZnO at a growth temperature of 70 °C, while, these rods were assembled together to form a flower structure at a higher growth temperature of 80 °C. Therefore, to tune the morphology of ZnO, temperature played a key role. After the successful deposition of cathode and anode, the final structure of the cell was fabricated. In order to study the performance comparison, the flexible cell on PET substrate was compared with the conventional ITO/Glass substrate based cell. It was found that the flexible cell showed comparable performance with a power conversion efficiency of 1.82%, and the bending cycle test depicted the excellent mechanical properties with good flexibility and power conversion efficiency of 1.78% even after 200 bending cycles. These studies revealed that the replacement of ITO, flexibility of the substrate, and the performance of the fabricated flexible cell would be an excellent inverted cell for future generation flexible device.