We studied that synthesis and characterization of poly benzodithiophenederivatives for efficient solar cells and organic thin film transistors
Firstly, the polymers were prepared through a Stille coupling reaction between the 4,8-bis(2-alkylselenophyl)-benzo-[1,2-b:4,5-b'']dithiophene (BDTSe) monomers and the 4,7-dibromobenzo [c] [1,2,5] thiadiazole (BD), 4,7-Dibromo-5,6-bis(octyloxy)benzo[c][1,2,5]thiadiazole (BDOR), 3-dibromo-5-octyl-4H-thieno[3,4-c]pyrrole-4,6(5H)-dione(TPD), 2-ethylhexyl 4,6-dibromothieno[3,4-b]thiophene-2-carboxylate (TTOR), 3,6-bis(5-bromothiophen-2-yl)-2,5-bis(2-decyltetradecyl) pyrrolo [3,4-c]pyrrole-1,4(2H,5H)-dione(DPP), 1-(4,6-dibromothieno[3,4-b]thiophen-2-yl)-2-ethylhexan-1-one (TT). All most the polymers are soluble in chloroform (CHCl3), chlorobenzene, and dichlorobenzene. Thermo gravimetric analyses (TGA) showed that all polymers are thermally stable with degradation temperature (Td) above 354 oC ~ 427 oC. Differential scanningcalorimetry (DSC) performed on all polymers did not reveal any noticeable thermal transitions. New polymers PBDTSe-BDOR, PBDTSe-TPD-C10, PBDTSe-TPD-C12, PBDTSe-TTOR, PBDTSe-DPP and PBDTSe-TT has narrow band gap 1.27 eV ~ 1.90 eV respectively. Organic photovoltaic performance based on two polymers were evaluated with configuration of ITO/PEDOT:PSS/polymer:PC71BM/LiF/Al. PBDTSe-BDOR and PBDTSe-TPD-C10 power conversion efficiency(PCE) of up to 2.66 and 4.4% were achieved under AM 1.5G simulated solar light (100 mW cm-2). A thin-film transistor with polymers (PBDTSe-BDOR, PBDTSe-TPD-C10, PBDTSe-TPD-C12, PBDTSe-TTOR, BDTSe-DPP and PBDTSe-TT) are found to exhibit typical p-channel FET characteristics with a hole mobility of 0.0043 cm2/Vs, 0.021 cm2/Vs, 0.0048 cm2/Vs, 0.0012 cm2/Vs, 0.14 cm2/Vs, 0.00044 cm2/Vs and an on/off ratio of 1.14×104, 2.62 x 106, 3.45 x 106 , 1.01×104, 7.81×104, 1.19×102 with a threshold voltage of -5.11 V, -2.42 V, -7.22, -18.01, -5.49, -15.11.
Secondly, we developed new donor materials in polymer with deep HOMO energy level. We have used stille coupling polymerization to synthesize a series of new crystalline deep HOMO level polymers, which are constituted of 2,6-Bis(trimethyltin)- 4,8-Bis(5-(2-bidodecyl)bithiophene-2-yl)benzo[1,2-b:4,5-b′]dithiophene (BDTBTh) as effective electron donor unit and 4,7-dibromobenzo [c] [1,2,5] thiadiazole (BD), 3-dibromo-5-octyl-4H-thieno[3,4-c]pyrrole-4,6(5H)-dione(TPD) units as electron acceptor units. The polymers exhibited low-lying highest occupied molecular orbital (HOMO levels, -5.58 ~ -5.60 eV) for high open circuit voltage(Voc) and Band gaps of PBDTBTh-BD and PBDTBTh-TPD were 1.63 and 1.82 eV, respectively. All the polymers are soluble in toluene, chloroform (CHCl3), chlorobenzene, and dichlorobenzene. Thermo gravimetric analyses (TGA) showed that all polymers are thermally stable with degradation temperature (Td) above 415 oC and 424 oC. Differential scanningcalorimetry (DSC) performed on all polymers did not reveal any noticeable thermal transitions. The OTFT and OPV characteristics of the other polymers will be fabricated.
Lastly, the polymers were prepared through a Stille coupling reaction between the 2,6-Bis(trimethyltin)-5-(2-7-alkyl)thienothiophene-2-yl)benzo[1,2-b:4,5-b′]dithiophene (BDTTT) monomers and the 3-dibromo-5-octyl-4H-thieno[3,4-c]pyrrole-4,6(5H)-dione(TPD), 3,6-bis(5-bromothiophen-2-yl)-2,5-bis(2-decyltetradecyl) pyrrolo [3,4-c]pyrrole-1,4(2H,5H)-dione(DPP). The three polymers(PBDTTT-DPP-C17, PBDTTT-TPD-C12 and PBDTTT-TPD-C17) are soluble in chloroform (CHCl3), chlorobenzene, and dichlorobenzene. Thermo gravimetric analyses (TGA) showed that all polymers are thermally stable with degradation temperature (Td) above 367 oC ~ 412 oC. Differential scanningcalorimetry (DSC) performed on all polymers did not reveal any noticeable thermal transitions. UV-vis absorption studies showed the maximum absorption at 700 nm in solution and 700 nm in film for PBDTTT-DPP-C17 and 624 nm in solution and 630 nm in film for PBDTTT-TPD-C12 and 636 nm in solution and 640 nm in film for PBDTTT-TPD-C17. All polymers has narrow band gap 1.49 eV ~ 1.83 eV
The OTFT and OPV characteristics of the other polymers will be fabricated.