Modification Of Active Layer And Interface In Non-fullerene Organic Photodetector

The rapid development of science and technology promotes the continuous progress of organic photodetectors(OPDs)which can realize the function of light/electricity conversion.The core of OPD is an organic photosensitive material,which usually adopts a bulk heterojunction(BHJ)structure composed of electron donors and electron acceptors.Traditional fullerene electron acceptors have disadvantages such as difficult chemical modification and limited absorption in the infrared region due to their molecular structure constraints,which hindering their further development.In contrast,non-fullerene materials have gained more and more attention due to their excellent properties such as chemical structure,tunable band gap and absorption band.In order to improve the performance of non-fullerene OPD devices,it is necessary to increase the photocurrent and suppress the dark current.The commonly adopted strategies are interface layer regulation and active layer modulation.In this dissertation,two OPDs were prepared based on the non-fullerene systems P3HT:ITIC-Th and PTB7-Th:TTD(DTC-2FIC)₂,and the device performance was optimized by hole transport layer modification and active layer modulation,respectively.The specific research contents are as follows:The inorganic hole transport layer MoO₃ was modified and optimized by the organic small molecule N,N'-Di(1-naphthyl)-N,N'-diphenyl-(1,1'-biphenyl)-4,4'-diamine(NPB),which effectively improved the performance of the OPD.By optimizing the NPB modified layer,the thickness was determined to be 20 nm.The addition of the modified layer improves the continuity and integrity of the thin film on the surface of the active layer,reduces the equivalent parallel resistance of the detector,and improves the electrons and holes at the two electrodes.At-0.1 V bias,the photocurrent density of the device at650 nm is improved by 19%,and the maximum value of responsivity and external quantum efficiency are 0.44 A/W and 75%,which obtained at 725 nm.In addition,due to the more reasonable energy level matching of the optimized device,the reverse injection of carriers from the electrode at bias is reduced,and the specific detectivity in the visible light band remains above 10¹¹ Jones.The structure and morphology of the non-fullerene active layer PTB7-Th:TTD(DTC-2FIC)₂ were optimized,and an OPD with visible-near-infrared broadband response was developed.After optimizing the active layer of the device,the film has the characteristics of uniform phase separation,low roughness,and?-?stacking orientation of face-on,which ensures the transport efficiency of carriers in the active layer and enables the device to obtain higher response and detection capabilities.Under the bias voltage of-0.5 V,the specific detectivity of the device in the 500-1200 nm band is over10¹¹ Jones,the response time and recovery time are 13?s and 4.5?s,and the linear dynamic range is 103 d B.In summary,the modification of the non-fullerene OPD hole transport layer and the regulation of the active layer can effectively improve the responsivity and specific detectivity of the device.The above scheme provides ideas and directions for the further optimization of non-fullerene OPD,and helps to promote the practical application of OPD.