Synthesis and photoelectric performance of D-A-A′ type small molecule based on triphenylamine

Abstract

A kind of novel D-A-A′ type organic small molecule TPA(BT-CNC8)2 based on triphenylamine was designed and synthesized, in which triphenylamine (TPA) was used as central donor (D) core, benzothiadiazole (BT) and i-octyl 2-cyanoacetate (CNC8) were used as main acceptor (A) and secondary acceptor (A′) units, respectively. Its optical physical properties, thermal stability and electrochemical properties were tested and systematically investigated via ultraviolet absorption spectra, thermal gravimetric analysis and cyclic voltammetry measurement, respectively. TPA(BT-CNC8)2 presented a wide absorption profile of 300–750 nm with an optical band gap of 1.65 eV. The highest occupied molecular orbital (HOMO) energy level of TPA(BT-CNC8)2 was calculated to −5.40 eV, which was mainly originated from the strong electron-withdrawing effect of benzothiadiazole and i-octyl 2-cyanoacetate units. The bulk-heterojunction organic solar cells of TPA(BT-CNC8)2-based was fabricated, in which TPA(BT-CNC8)2 was used as donor material while PC71BM as acceptor material, in the absence of optimizing device structure, its power conversion efficiency (PCE) reached to 1.62% together with a short circuit current density (Jsc) of 6.94 mA cm−2 and open circuit voltage (Voc) of 0.81 V. Further improvements of the device efficiency by optimizing the devices structure, using solvent additive or thermal annealing are currently under investigation.