| Since the discovery of the ultrafast photo-induced charge transfer between conjugatedpolymers (CPs) and fullerene, the polymer bulk heterojunction photovoltaic cells (PVCs)have attracted much attention due to the potential application for large area, flexible, andlow-cost solar cells. Tremendous efforts such as the development of novel low band gap(LBG) CPs, the optimization of the fabricating process and modifying the morphology of thedonor and acceptor blend etc., have been devoted to improve the power conversionefficiencies (PCE) of PVCs. Among them, the development of high performancedonor-acceptor (D-A) type LBG CPs has been demonstrated the most vigorous approach toachieve the efficient PVCs.In the dissertation, we have design and synthesis novel dithieno[2,3-d:2′,3′-d′] benzo-[1,2-b:4,5-b′]dithiophene-based (DTBDT) derivates, and obtained several conjugatedpolymers reacted with different narrow band gap monomers by Stille coupling reaction. Thechemical structures were characterized and the optical-electrical properties were investiaged.The main content are as following:In chapter2, the optoelectronic properties of DTBDT derivates and CPs derived fromDTBDT derivates and DPP could effectively and rationally be tuned by the flanking ofDTBDT by alkyloxy,4,5-didecylthieno-2-yl, and trialkylsilylethynyl substituent groups. TheHOMO levels of DTBDTs were deepened from–5.21eV to–5.36eV and then dropped to–5.66eV, and HOMO energy levels of the CPs based on DTBDTs (PBT-HD-DPP-C16,PBT-T-DPP-C12and PBT-TIPS-DPP-C16) were deepened from–5.13eV,–5.19eV and thendropped to–5.25eV while the DTBDT were accordingly flanked by the alkyloxy,4,5-didecylthieno-2-yl and TIPS substituent groups. Meanwhile, it was also found that, theflanking of DTBDT TIPS substituent group provides PBT-TIPS-DPP-C16exhibiting thelowest HOMO level, narrowest band gap and comparatively high mobility among the threeDTBDTs-based CPs. As the consequences, the PVCs based on PBT-TIPS-DPP-C16andPC71BM blend show the highest Voc of0.76V, the highest Jsc of13.9mA/cm2and PCE of6.39%in the optimized PVCs using PBT-TIPS-DPP-C16, PBT-HD-DPP-C16and/orPBT-T-DPP-C12as the electron donor materials and PC71BM as the electron acceptormaterials.In chapter3, The resulting D-A copolymer PBT-T-DTNT was obtained by Stillecoupling polymerization of5,10-bis(4,5-didecylthien-2-yl)dithieno[2,3-d:2′,3′-d′]benzo-[1,2-b:4,5-b′]dithiophene (DTBDT-T) and3,7-di(3-hexylthiophen-5-yl)-naphtho[1,2-c:5,6-c]-bis[1,2,5]thiadiazole (DTNT). The polymer was soluble in1,2-dichlorobenzene andexhibited good thermal stability up to420℃. The optical band gaps of the polymerPBT-T-DTNT was1.47eV. The oxidation potential of the polymer PBT-T-DTNT was0.51V. The EHOMOand ELUMOof the polymer PBT-T-DTNT was-5.22eV and-3.75eV, respectively.And, the inverted PVCs based on PBT-T-DTNT and PC71BM blend show better Voc, better Jscand PCEs than the upright PVCs based on PBT-T-DTNT and PC71BM blend usingPBT-T-DTNT as the electron donor materials and PC71BM as the electron acceptor materials.And, the best inverted PVCs shows a PCE of7.52%, its efficiency is close to existing reportsnew materials advanced level of development.In chapter4, the resulting D-A copolymers PBT-T-ID-C12, PBT-T-TTS-C16andPBT-T-TTC-C8were obtained by Stille coupling polymerization of DTBDT-T as the electrondonor,6,6′-dibromo-N,N′-(2-butyloctyl)-isoindigo (ID-C12),4,6-dibromo-2-(2-hexyldecyl-sulfonyl)thieno[3,4-b]thiophene (TTS-C16),1-(4,6-dibromothieno[3,4-b]thiophen-2-yl)-2-ethylhexane-1-one (TTC-C8) as the electron acceptor. These polymers show good absorbanceperformance in the range of400–900nm, and characterized by UV-Vis, photoluminencespectrum, and cyclic voltammetry. |
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