A star-shaped electron acceptor based on 5,5′-bibenzothiadiazole for solution processed solar cells

A novel star-shaped molecule based on triphenylamine as the core and 5,5-bibenzo[c][1,2,5]thiadiazole as arms (S(TPA-BBT)) was synthesized and investigated as an electron acceptor in solution-processed organic solar cells. The compound S(TPA-BBT) shows excellent thermal stability with a decomposition temperature of 353 degrees C. S(TPA-BBT) in chloroform solution exhibits two absorption peaks at 326 and 450 nm, which red shifts to 334 and 482 nm in thin film, respectively. The HOMO and LUMO energies are estimated to be -5.48 and -3.10 eV, respectively, from electrochemistry, and match with those of poly(3-hexylthiophene) (P3HT). Solution-processed solar cells based on P3HT: S(TPA-BBT) after annealing at 150 degrees C for 10 min yield power conversion efficiencies up to 0.81%.