Synthesis and photovoltaic properties of organic small molecules containing triphenylamine and benzothiadiazole moieties with different terminal groups

• Three organic small molecules were synthesized and applied in BHJ solar cells.
• The introduction of different terminal groups can tune the absorption spectra.
• The organic molecule (TPA-DTBT) showed a power conversion efficiency of 1.85%.

Three new organic small molecules (TPA-DTBT, TPA-DTBT-TH and TPA-DTBT-CAO) containing triphenylamine (TPA) and 4,7-bis(thiophen-2-yl)benzo[1,2,5]thiadiazole (DTBT) moieties with different terminal groups were designed and synthesized. Their thermal, photophysical, electrochemical and photovoltaic properties were investigated. The introduction of 2-ethylhexyl cyanoacetate and 2-tetradecyl thiophene as terminal groups extended molecular π-conjugation length and broadened the absorption spectra. Three small molecules exhibit good solubility in common organic solvents, good film-forming ability, and thermal stability. Bulk heterojunction (BHJ) solar cells based on the blend of small molecule TPA-DTBT and PC61BM showed a power conversion efficiency (η) of 1.85%.

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