Effect of the mode of fixation of the thienyl rings on the electronic properties of electron acceptors based on indacenodithiophene (IDT)

Effect of the Terminal Acceptor Unit on the Performance of Non-Fullerene Indacenodithiophene Acceptors in Organic Solar Cells

“…The electrochemically estimated HOMO-LUMO energy gap (E g e ) along with optical data for IDT-1 and IDT-4 show that insertion of an indanone unit between IDT and dicyanovinylene in IDT-4 changes the LUMO level alone, suggesting that the HOMO level is mainly related to the IDT core, while the LUMO of the compounds is sensitive to the nature of the acceptor group. The same trend is supported by DFT predictions: the electrochemical gaps are ~0.35-0.5 eV lower compared to the calculated HOMO-LUMO gap, which might be caused by the different nature of the processes involved in the reduction of the compounds [24]. For all synthesized compounds the LUMO levels are consistent with that of PC 60 BM derivatives, as shown in Figure 3b, suggesting their suitability for being used as n-type semiconductors in BHJ OSCs with P3HT.…”

“…Scheme 1 reveals the synthetic procedure of the target compounds. IDT-1 [24] and IDT-4 [25] were already reported in the literature. The IDT building block was prepared using a previously described multi-step synthetic protocol [24].…”

“…IDT-1 [24] and IDT-4 [25] were already reported in the literature. The IDT building block was prepared using a previously described multi-step synthetic protocol [24]. Firstly, 2,5-di(thiophen-2-yl) terephthalate 6 was obtained in 79% yield by reacting diethyl 2,5-dibromoterephthalate 5 with tributyl(thiophen-2-yl)stannane.…”

“…Compounds 2,3 [26], 4 [27], 6, 7, 8, IDT-1 [24], and IDT-4 [25] were obtained using known procedures.…”

“…Recently, we reported the synthesis and optoelectronic properties of three A-D-A-type NFAs based on the IDT platform and the dicyanovinylene terminal groups, corresponding to three different ways of connecting the thienyl rings to the central phenyl unit of the IDT block [24]. With these results in hand, our next goal was to improve the optoelectronic and photovoltaic properties by modulating the terminal groups.…”