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Title: Design, synthesis and characterization of novel low band gap conjugated polymers for use in bulk heterojunction photovoltaic solar cells
Author: Manji, Athanasius Justin
Awarding Body: Bangor University
Current Institution: Bangor University
Date of Award: 2012
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This work details the synthesis of a functionalised all-donor polymer, poly(3- hexylthioacetate thiophene) (P3HTT) [42] along with four new donor-acceptor (D-A) copolymers. Two of the four copolymers are based on fluorene (F) and carbazole (C) as electron donors copolymerised with DEBT to give, PFDEBT [62] and PCDEBT [63] respectively, while the other two are based on the same electron donors, but copolymerised with DES to give PFDES [64] and PCDES [65] respectively. All the polymers exhibited good solubility in common organic solvents and good thermal stability. The spectrophotometry analysis of polymer [42] in chloroform showed that it emits in the green region with 26% photoluminescence quantum yield (PL values, 28 % and 27 % respectively. In contrast, copolymers [64] and [65] have single broad absorption band and emit in the green region with PL values of 55 % and 51 % respectively. The electrochemical responses of the polymers were measured using cyclic voltammetry. The results obtained for polymer [42] were different from what was expected; its band-gap was similar to that of P3HT and its energy levels were elevated. In contrast, the band-gaps of the copolymers were tuned in the range of 1.47 to 1.65 eV The results showed that the acceptor units have exhibited the same effect of band-gap lowering in the two sets of the copolymers, for instance, the LUMO energy level of copolymers [62] and [63] is - 3.32 eV and those of copolymers [64] and [65] is - 3.57 eV Conversely, different effect was observed in the values of the HOMO energy levels, for example, the values for [62] and [64] which contain the same donor (fluorene) are - 4.86 and - 5.07 eV respectively; while those of copolymers [63] and [65] composed of carbazole are - 4.97 and - 5.04 eV respectively. This may suggest that the acceptor unit reduced the band-gap by lowering the LUMO energy level but at the same time elevated the HOMO energy level probably due to the presence of EDOT.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available