Dual functionality of metal-tetraphenylporphyrin in ZnO-based hybrid thin film transistors

Complementary hybridization of ZnO thin films with aluminum tetraphenylporphyrin (Al(III)TPP), zinc tetraphenylporphyrin (Zn(II)TPP) and H2TPP (tetraphenylporphyrin) was adopted for tuning the hybrid thin film transistor (TFT) performance and improving their flexibility. After the hybridization with the organic layers, the chemical and structural features of ZnO thin films were well-preserved as compared with those of solely ZnO thin films. The existence of organic layers was monitored by X-ray photoelectron spectroscopy depth profiling. We fabricated the TFT based on ZnO/organic layers, resulting in the on-off ratio and threshold voltage of the devices manipulated by selecting the organic layers. These results can be understood by the performance tuning mechanisms related with the electron charge transfer induced by a work function difference. Remarkably, a significant improvement of the flexibility in the hybrid films was achieved without any significant loss in optical transmittance, which will be high demand in transparent and flexible electronics.