Fluorinated Dielectrics-Modulated Organic Phototransistors and Flexible Image Sensors

It is generally believed that the incorporation of fluorine functional groups into dielectrics can effectively impede the charge-trapping process and improve carrier mobility. However, the relationship between the device performance and fluorinated groups is still not clear and also the modulation effect of fluorine functional groups on photogenerated charge carrier in phototransistors has not yet been investigated. Herein, phototransistors are constructed by using three kinds of gate dielectric layers with different fluorinated groups to exploit the effect of fluorine functional groups. It is concluded that the presence of fluorinated groups indeed increases the transistor mobility and optical figures of merit in phototransistors compared to the device with a fluorine-free dielectric layer. Concurrently, the exciton binding energy is increased with the addition of fluorinated groups, resulting in the decrease of phototransistor performance compared with less content of fluorinated groups due to the synergistic balance effect of fluorine functional groups. The results further clarify how the fluorine functional groups optimize the interface of organic phototransistors and modulate the photoelectric performance.