Synthesis And Characterization Of Narrow Band-gap Conjugated Polymers For Polymer Photodetectors With High Sensitivity And Wide Spectral Response

In recent years, the conjugated polymer photodetectors have attracted much attention to academia and industry due to the advantages such as:low cost, light weight, easy fabrication, and it can be obtained high sensitivity, high response speed, wide spectral response of the multicolor devices of large area. Over the past few years of research and development, part of performance of polymer photodetectors can be compared to inorganic detectors, the spectral response range covered more than1000nm extends to near infrared region. At present due to the study of performance and the working life of the device is not perfect, so it is not really applied to science and technology, industry and other fields. But the development prospect of polymer photodetectors is significant, developing the new polymer materials, improving device performance and working life in order to realize emerging light detector application has become the scientific researchers with unremitting efforts to achieve target.In this dissertation, a kind of polymer photovoltaic detector materials with wide spectral response were synthesized, and its spectral response extends to near-infrared light district1300nm, in addition, several kinds of conjugated polymers have also been synthesized, and their structures, optical and electrical performance were characterized and studied.In chapter3, the narrow band gap conjugated polymers PBDT-BTQ (Eg=0.98eV)and PBDT-BTQ-BT((Eg=0.93eV)) were synthesized by Stilling coupling reaction, which derived from2,3-Bis(4-octyloxyphenyl)-5,8-dibromothiadiazolquinoxaline,2,6-Bistrimethyltin-4,8-dioctylbenzo[1,2-b:4,5-b’]dithiophene and4,7-dibromo-2,1,3-benzothiadiazole. These two kinds of polymers in the solid film has a wide spectrum of absorption are respectively380nm-1300nm and380nm-1320nm. The oxidation potential of copolymer PBDT-BTQ as0.62V. The values of highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) are-5.05eV and-4.07eV. The oxidation potential of copolymer PBDT-BTQ-BT as0.52V. The values of highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) are-4.95eV and-4.03eV. Device structure of polymer PBDT-BTQ-BT is ITO/PEDOT:PSS/PBDT-BTQ-BT:PC71BM/Ca/Al, the open circuit voltage, short circuit current density, photoelectric conversion efficiency of the device (0.1%) is low, still need further optimization of device structure or find more matching acceptor materials, in order to improve the performance of the device. The spectral response of the device to achieve the near infrared area of1300nm.In chapter4, the conjugated polymers named as PBDT-BIF(Eg=2.22eV)and PBDT-BQ(Eg=1.78eV) were synthesized by Stilling coupling reaction which derived from2,6-Bistrimethyltin-4,8-dioctylbenzo[1,2-b:4,5-b’]dithiophene and2,3-bis[4-(3,7-dimethyl-octyloy)phenyl]-5,8-dibromoquinoxaline,2,7-Dibromo-11,12-bishexadecyloxydibenzo[a,c] Phenazine. The copolymers have good solubility, soluble in common organic solvents such as chloroform, toluene. Thin solid films of copolymer PBDT-BIF absorption peak at413nm 498nm and455nm, The absorption peak of thin solid films of copolymer PBDT-BQ were386nm and620nm. The values of highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of PBDT-BIF are-5.26eV and-3.04eV, the values of highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of PBDT-BQ are-5.22eV and-3.44eV.In chapter5, the narrow band gap conjugated polymers named as PF-DOTBTT(Eg=1.77eV), PIF-DOTBTT(Eg=1.83eV), PCZ-DOTBTT(Eg=1.76eV) were synthesized by Suzuki coupling reaction which derived from2,5-bis[7-(5-bromo-4-octylthiophene-2-yl)benzothiadiazole-4-yl]thiophene(DBrDOTBTT) and9,9-dioctyl-2,7-dibromofluorene(F),6,6’,12,12’-tetraoctylindenofluorene (IF), N-9’-heptadecanyl-2,7-dibromocarbazole (CZ). The copolymers present good solubility, soluble in common organic solvent such as THF, toluene etc. Polymer PF-DOTBTT has two absorption peaks in the toluene solution, respectively in364nm and550nm, red shift occurred solid film absorption, respectively in379nm and588nm. Polymer PIF-DOTBTT has two absorption peaks in the toluene solution, respectively in370nm and546nm, red shift occurred solid film absorption, respectively in381nm and577nm. Polymer PF-DOTBTT has two absorption peaks in the toluene solution, respectively in365nm and561nm, red shift occurred solid film absorption, respectively in382nm and595nm. The values of highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of PF-DOTBTT, PIF-DOTBTT, PCZ-DOTBTT are-5.46eV and-3.69eV,-5.53eV and-3.70eV,-5.43eV and-3.67eV.