Starburst Triphenylamine‐Based Donor–Acceptor‐Type Small Molecules for Solution‐Processed Organic Solar Cells

Abstract A class of the donor–acceptor (D–A)‐type organic small molecules that includes TPA‐DPP, DTPA‐DPP, and TTPA‐DPP [TPA = triphenylamine, DPP = diketopyrrolopyrrole, DTPA = bis(triphenylamine), TTPA = tris(triphenylamine)] was synthesized; these compounds contain TPA as a donor unit and DPP as an acceptor unit. Solution‐processed organic solar cells (OSCs) with these compounds as donors and [6,6]‐phenyl‐C 71 ‐butyric acid methyl ester (PC 71 BM) as an acceptor were fabricated. The starburst OSCs prepared from DTPA‐DPP and TTPA‐DPP with two and three TPA units, respectively, exhibited better photovoltaic performance than the OSC prepared with one TPA unit, because DTPA‐DPP and TTPA‐DPP have better light‐harvesting properties and charge‐transport properties. The DTPA‐DPP‐based OSCs delivered a power conversion efficiency (PCE) of 2.26 % and the TTPA‐DPP‐based OSCs exhibited a higher PCE of 2.47 %. The PCE level is 1.15 and 1.25 times higher than that in the TPA‐DPP‐based OSCs, respectively. Our work indicates that a starburst configuration can improve the photovoltaic properties of D–A‐type organic small molecules in OSCs.