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Barbiturate derivatives for self-assembly in photovoltaic-effective organic layers

Oliveira, B. ; Morgado, J. ; Charas, A.

Barbiturate derivatives for self-assembly in photovoltaic-effective organic layers , Proc Sociedade Portuguesa de Química EuChemS Chemistry Congress (ECC8) ECC8, Lisbon, Portugal, Vol. , pp. - , August, 2022.

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Abstract
Organic photovoltaic (OPV) devices represent an interesting clean and renewable energy technology due to involving low-cost fabrication techniques and enabling the manufacturing of semi-transparent, mechanically flexible, and lightweight solar modules. These advantageous characteristics are related with the properties of the organic layer, which combines soluble organic semiconductors with complementary electronic properties (one performing as electron donor and the other as electron acceptor), highly absorbing the solar radiation. Because the OPV device performance greatly depends on the active layer morphology, i.e. the organization of the organic semiconductors, at the nanoscale, the optimization and stabilization of the active layer´s morphology is crucial to produce devices with reproducible high efficiency and long-term stability. One approach to reach high efficiency and morphological stability in OPV’s organic layers relies on the formation of supramolecular structures of the donor and the acceptor semiconductors complying with the optimal morphological characteristics, that is, donor/acceptor interfaces should be accessible within ca. 10 nm from the excitons photogenerated either in the donor or in the acceptor. In this communication, we present the synthesis of derivatives of one of the most efficient acceptors used in OPV devices, ITIC (2,2′-[[6,6,12,12-tetrakis(4-hexylphenyl)-6,12-dihydrodithieno[2,3-d:2′,3′-d′]-s-indaceno[1,2-b:5,6-b′]dithiophene-2,8-diyl]bis[methylidyne(3-oxo-1H-indene-2,1(3H)-diylidene)]]bis[propanedinitrile]), containing molecular recognition motives for self-assembling, through hydrogen bonds, and forming both morphologically stable and PV-effective donor-acceptor supramolecular systems. The synthesised compounds contain barbiturate moieties, these being prone to form directional and stable assemblies with (complementary) melamine-containing donors. The barbiturate derivatives, one symmetrical, composed of two barbiturate end-groups, and another one asymmetrical, containing only one modified end-group, were prepared through microwave-assisted condensation reactions of barbituric acid and ITIC precursor compounds. The UV-visible absorption spectra of the new compounds and their electrochemical properties, relevant for applications in OPV devices, are also presented.