Research On Double-gate Photosensitive Organic Field Effect Transistor Based On Polyvinyl Alcohol Gate Dielectric

Compared with photosensitive organic diodes,photosensitive organic field effect transistors（PhOFETs）have higher sensitivity,photoresponsivity and lower noise current,which exhibit great potential applications in low-cost,flexible,large-area display,sensing electronic devices and other fields.Compared with the conventional single-gate PhOFET,the double-gate PhOFET has two controllable conduction channels,which brings high gain,broad spectral response and more flexible applications.The current double-gate PhOFET mostly uses opaque Si/Si O₂sheets as gate and gate dielectric,and the light must be incident from the top of the device,which has higher requirements on the transmittance of the top gate dielectric and gate,which increases difficulty of the device preparation.In order to overcome the shortcomings of the above devices,this work focuses on the polyvinyl alcohol（PVA）gate dielectric double-gate PhOFET,and has achieved some innovative results.（1）A new process of preparing PVA thin film on small molecular organic film was developed.Based on this,a top-gate PhOFET based on PVA gate dielectric and single-layer CuPc photosensitive layer was developed.The results show that the responsivity and specific detectivity of the top-gate device under red light illumination of 0.276μW/cm² reach 87.4 A/W and 1.24×10¹³ Jones,respectively,which are greater than the corresponding parameters of the bottom-gate device(76.5A/W and 6.98×10¹² Jones,respectively).（2）A double-gate OFET based on PVA top and bottom gate dielectrics and single-layer CuPc film photosensitive layer was successfully developed.The device performance in top-gate mode and bottom-gate mode is comparable to that of single-top-gate and single-bottom-gate devices,respectively.In the common gate voltage mode,due to the existence of two conductive channels,the responsivity is as high as 138.7 A/W,which is 62.2 A/W higher than that of the single bottom gate device and 51.3 A/W higher than that of the single top gate device.In the double-gate mode,in the case of a fixed top gate voltage,under the regulation of the bottom gate voltage,with the increase of the bottom gate voltage,the dark current and photocurrent of the device gradually increase;and vice versa.（3）A double-gate PhOFET with PVA gate dielectric and CuPc/SnPc heterojunction photosensitive layer was developed.The photodetection performance of the device in the double-gate mode is studied.When the top-gate channel is on and the bottom-gate channel is off,the device mainly responds to 905 nm light with a responsivity of 23.5 A/W.When the gate channel is turned off and the bottom gate channel is turned on,650 nm is the main detection band,and its responsivity reaches112.3 A/W.The device has better red light and near-infrared light resolution in the double-gate mode.The responsivity ratios of the device to 905 nm and 650 nm light are 10.52 and 38.73,respectively,which are higher than those in the single-gate mode（2.50 and 17.63）.