Synthesis And Characterization Of UV-NIR Polymer Photodetector Materials

In recent years,studies have found that by designing and synthesizing narrow bandgap conjugated polymers with adjustable energy levels,band gaps,charge transport properties,etc.,organic polymer photodetectors with wider spectral response and higher sensitivity can be prepared（PPDs）,so that these polymer-based detectors have a continuous wide-band operating range,this feature happens to overcome the operational complexity of the combination of multiple detectors based on inorganic materials.In addition,similar to polymer solar cells,PPDs can also use bulk heterojunction structure（BHJ）,that is,the active layer is prepared by blending the donor and the acceptor,and the The ultra-fast charge transfer makes PPDs have the characteristics of fast response and high sensitivity.Based on the above advantages,new conjugated polymer photodetector electron donor and acceptor materials are widely studied.In the second chapter,a new narrow-band-gap conjugated polymer POT-DPP was obtained by reacting the electron acceptor 2,5-bis（2-decyltetradecyl）-3,6-bis（thien-2-yl）-2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-Dione（DPP）with the electron donor3,3’-dimethoxy-2,2’-bithiophene through Stille polymerization.The test results show that the absorption range of the polymer is 600-1100 nm,the band edge is at 1020 nm,the optical band gap（E_g）is 1.22 eV;the measured HOMO energy level is-4.83 eV and the LUMO energy level is-3.61 eV;the temperature-variable absorption and X-ray diffraction test of the polymer showed that the polymer can show obvious aggregation behavior in the state of solution and film;then the polymer is used as the electron donor,and the fullerene derivative[6,6]-phenyl-C71-methyl butyrate(PC₇₁BM)is used as the electron acceptor to prepare the polymerphotodetectordevice.Thedevicestructureis ITO/ZnO/POT-DPP:PC₇₁BM/MoO₃/Ag,the optimal weight ratio for the acceptor and receiver is 1:1.5,the volume ratio of the solution additive DIO is 2%,and the optimal annealing temperature is 130℃.The photovoltaic performance at this time is:V_oc=0.32 V,J_sc=15.06 mA/cm²,FF=55.99%,PCE=2.71%,and the polymer photodetector is under0V bias,PFN is used as the cathode modification layer,and the detection rate（D*）in the spectral response range（400-950 nm）is close to 10¹⁴ Jones;under-0.1V bias,in the 400-950nm,the cathode modification layers are PFN,ZnO,and PFN/ZnO.The D*of all device structures is above 10¹¹ Jones;under-0.5V bias,in the 400-950 nm range,three different cathode modification layers The D*reached 10¹⁰ Jones,and the D*of the device made of PFN/ZnO as the cathode modification layer reached 10¹¹ Jones.And the responsiveness and linear dynamic range of this polymer photodetector device show good performance.In the third chapter,two new narrow band gap polymers were obtained by reacting2,3-bis（4-（2-octyl）dodecyloxyphenyl）-5,8-dibromobenzothiadiazopyrazine（TQ）of electron acceptor unit based on benzopyrazine unit with unoptimized electron donor thiophene（T）and thieno[3,2-b]thiophene（TT）by Stille polymerization Conjugated polymers PTQ-T,PTQ-TT.The test results show that the absorption range of the two polymers in the solution is about600-1900 nm,the band edges extend to nearly 2000 nm,and the E_g is 0.67 eV（PTQ-T）and0.62 eV（PTQ-TT）,respectively;the polymer photodetector device is made of two polymers acting as active layers,the device structure is ITO/ZnO/pure donor/MoO₃/Ag.The EQE of the polymer PTQ-TT at 1000nm is 0.127%,which is higher for polymer PTQ-T（0.077%）;the photodetector device with the device structure of ITO/ZnO/active layer:PC₆₀BM/MoO₃/Ag made of polymer PTQ-T and PC₆₀BM,after adding the solvent additive DIO（1%）,its measured at 1000 nm EQE is 0.2%,dielectric constant at 105 Hz is 6.4,V_OC is 0.17 V,J_SC is0.66 mA/cm²,FF is 38%,dark current at-1V is 4.87×10^-4 A/cm²;not added DIO has an EQE of 0.18%and a dielectric constant of 5.1 at 10⁵ Hz.In the fourth chapter,a new narrow band gap is obtained by reacting the electron acceptor（E）-2,2’-2bromo-4-4’-2（2-decyl-dodecyl）-（6,6’-2thieno[3,2-b’]pyrrole）-5,6-dione（TIIG）containing thiophene-isoindigo（TII）with the electron donor3,3’-dimethoxy-2,2’-bithiophene through Stille polymerization Conjugated polymer PTIIG-DTO.The test results show that the absorption range of the polymer is 400-1600 nm,the band edge is at 1600 nm,the optical band gap（E_g）is 0.775 eV;the measured HOMO energy level is-4.433 eV,and the LUMO energy level is-3.665 eV;the dielectric constant at10⁵ Hz is 11.6;The polymer photodetector with the device structure of ITO/ZnO/pure donor/MoO₃/Ag composed of the pure polymer alone as the active layer has an EQE of 0.18%at 1000 nm.