Synthesis And Application In Organic Photovoltaic Of Conjugated Polymers Based On “Thiophene-Benzene-Thiophene”

Over the past decade, conjugated polymer solar cells(PSCs) have been widely investigated as one of the potential renewable energy sources with the advantages, such as low-cost, light-weight, flexible and solution processable. Indacenodithiophene(IDT) based donor units, which is one member of the thiophene-benzene-thiophene family, showed excellent performance in the field of organic photovoltaics owing to their planar structure and large ?-conjugated system. In this manscript, two novel “thiophene-benzene-thiophene” building blocks were prepared and utilized as the donor unit for conjugated polymer construction. Based on it, a series of novel polymers were prepared and via device optimization, the relationship between the structure and the photovoltaic performance was investigated. The details are as following:Part?: Synthesis and Photovoltaic Properties of DMIDT based Conjugated PolymersIn order to reduce the steric hindrance from the side chain and enlarge the ?-conjugated system, two novel thiophene-benzene-thiophene building blocks were designed and prepared via inserting methylene bridge into the IDT segment and introducing different side chains. Through Stille polymerization, a series of new conjugated polymers were obtained. These polymers were characterized by 1H NMR and their molecular weights, UV-vis, electrochemical, thermal and photovoltaic performance were investigated. Among these polymers, PDPMIDT-1 presents the best PCE of 1.78%(Voc=0.80 V, Jsc=4.53 mA/cm2, FF= 0.49).Part?: Synthesis and Characterization of Novel DMIDT-based Conjugated PolymersIn Part?, it's known that alkyl benzene modified DMIDT is a potential candidate for high performance donor materials, so herein we designed and synthesised a series of D-A type conjugated polymer materials based on this novel building block. The polymers were characterized by 1H NMR and their molecular weights, UV-vis, electrochemical, thermal and photovoltaic performance were investigated. Among these polymers, after device optimization, PDPMIDT-3 presents the best PCE of 8.26%(Voc=0.89 V, Jsc=13.40 mA/cm2, FF= 0.70).Part ?: Synthesis and Characterization of Novel Benzopyran-based Conjugated PolymersFluorene is a common building block for material design in organic electronics. In this section, an oxygen atom was introduced into the fluorene unit and a new donor unit was generated i.e. dibenzopyran(DBP). Based on it, two D-A typed conjugated polymers(PDBPTBT-1 and PDBPTBT-2) were designed and prepared successfully. The polymers were characterized by 1H NMR and their molecular weights, UV-vis, electrochemical, thermal and photovoltaic performance were investigated. The performance of PDBPTBT-1/PC71 BM showed a PCE of 2.88% with the introduction of a TiOx thin layer as an optical spacer.Part ?: Synthesis of Novel Pyran Fused "thiophene-benzene-thiophene" building block and its Application in Polymer Solar CellsBased on the study in Part ?, the introduction of the oxygen atoms may produce some potential candidate for high photovoltaic performance. So herein, two oxygen atoms are introduced into the IDT unit and a novel “thiophene-benzene-thiophene” monomer is successfully prepared. Then, a series of D-A type conjugated polymers have been prepared via the Stille and/or Suzuki polymerization. The polymers were characterized by 1H NMR and their molecular weights, UV-vis, electrochemical, thermal and photovoltaic performance were investigated. After device optimization, PBDTP-DTDFBT showed a best PCE of 7.26%(Voc=0.72 V, Jsc=15.30 mA/cm2, FF= 0.66) among these polymers.Part ?: Synthesis and Characterization of the Random Terpolymers based on the Novel Pyran MonomerTerpolymer is an efficient strategy for fine tune of the HOMO\LUMO properties, absorption spectra, solubility etc. In order to adjust the absorption spectra of the final polymers, three random terpolymers were designed and synthesized. All polymers presented intense absorption in the region of 400-800, which matches the sunlight really well. Among these polymers, PBDTP-1 presents the best PCE of 3.63%(Voc=0.71 V, Jsc=10.73 mA/cm2, FF=0.48).