Design of new benzothiadiazole-based linear and star molecules with different functional groups as solar cells materials: A theoretical approach

The novel linear and star molecules based on benzothiadiazole as a central core, TPA as end groups and different functional groups as π-spacers were theoretically examined in the OSC applications. The geometry structures in ground and excited state, ionization potentials (IPs), electron affinities (EAs) and reorganization energy (Eλ+ and Eλ−) of linear and star molecules were studied by DFT methods. The absorption and the emission spectra were calculated by TD-BHandHLYP method. Star molecules based on ethynyl groups as π-spacer exhibit ameliorative IPs, EAs, Eλ+ and Eλ−, indicating they are more suitable for the formation and transfer of holes than the others. Moreover, the diethynyl groups improve the charge transfer character and extend the absorption wavelength towards the range with the maximum photon flux.

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► The novel linear and star molecules based on benzothiadiazole as a central core, TPA as end groups and different functional groups as π-spacers were theoretically investigated.
► The analyses of IPs, EAs, Eλ+ and Eλ− indicate the little IPs, Eλ+ and Eλ− and the great EAs for BSEP and BSEEP with ethynyl groups, is more suitable for generating hole, and charge transfer as p-type materials.
► The ethynyl groups improve the absorption wavelength towards the range with the maximum photon flux.