Synthesis of novel indacenodithiophene derivatives and their application in organic solar cells
File(s)
Author(s)
Ufimkin, Petr
Type
Thesis
Abstract
Organic semiconductors have risen as a promising replacement for silicon in electronic applications. They benefit from increased flexibility, transparency, and the potential for cheaper device production. Particularly, the field of organic photovoltaics (OPV) has seen tremendous progress, with power conversion efficiencies (PCEs) over 19% being reported for single junction devices. Much of their performance growth has been driven by the synthetic modification of non-fullerene acceptors (NFAs). 3,9-Bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2’,3’-d’]-s-indaceno[1,2-b:5,6-b’]dithiophene (ITIC) is a high-performing example of these and the development of novel electron donating cores and NFAs based on its structure is the focus of this work.
In Chapter 2, a series of indacenodithiophene (IDT) derivative cores were synthesised via a novel route utilising a triflic acid ring-closing reaction. This is more direct than earlier reported synthetic pathways, with synthesis of indacenodithienothiophene (IDTT) taking two steps fewer and proceeding in 66.8% overall yield instead of 9.4%. Three main synthetic strategies were applied in the design of novel cores: ring-extension, fluorination, and isomerisation. Overall, six cores were synthesised, with four entirely novel and two having their synthesis optimised. In addition, a route to asymmetric alkyl-chain IDT was developed.
NFAs with the ITIC structure were then synthesised in Chapter 3 with modification by side chain engineering, end-group fluorination, core fluorination, and end-group replacement. The NFAs were taken to our sponsor’s site and screened in large-area devices. Because of observed poor acceptor solubilities, derivatives were then produced with longer sidechains. Further testing and optimisation were performed on small-area devices. The novel C8-2FITIC acceptor performed at a respectable 8.3% PCE but trailed the performance of NFAs previously prepared in our group.
Finally, in Chapter 4, the fluorinated p-type polymer P2FIDTT-BT was synthesised from the novel 2FIDTT core and tested in OFET devices. The polymer had a saturated mobility (µsat) of 0.29 cm2/Vs in devices and a threshold voltage (VT) of -29 V.
In Chapter 2, a series of indacenodithiophene (IDT) derivative cores were synthesised via a novel route utilising a triflic acid ring-closing reaction. This is more direct than earlier reported synthetic pathways, with synthesis of indacenodithienothiophene (IDTT) taking two steps fewer and proceeding in 66.8% overall yield instead of 9.4%. Three main synthetic strategies were applied in the design of novel cores: ring-extension, fluorination, and isomerisation. Overall, six cores were synthesised, with four entirely novel and two having their synthesis optimised. In addition, a route to asymmetric alkyl-chain IDT was developed.
NFAs with the ITIC structure were then synthesised in Chapter 3 with modification by side chain engineering, end-group fluorination, core fluorination, and end-group replacement. The NFAs were taken to our sponsor’s site and screened in large-area devices. Because of observed poor acceptor solubilities, derivatives were then produced with longer sidechains. Further testing and optimisation were performed on small-area devices. The novel C8-2FITIC acceptor performed at a respectable 8.3% PCE but trailed the performance of NFAs previously prepared in our group.
Finally, in Chapter 4, the fluorinated p-type polymer P2FIDTT-BT was synthesised from the novel 2FIDTT core and tested in OFET devices. The polymer had a saturated mobility (µsat) of 0.29 cm2/Vs in devices and a threshold voltage (VT) of -29 V.
Version
Open Access
Date Issued
2022-03
Date Awarded
2022-11
Copyright Statement
Creative Commons Attribution NonCommercial NoDerivatives Licence
Advisor
Heeney, Martin
Sponsor
Merck & Co.
Publisher Department
Chemistry
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)