A new V-shaped triphenylamine/diketopyrrolopyrrole containing donor material for small molecule organic solar cells

Abstract

A new V-shaped small molecule, TPA(DPPT2)2 is designed and synthesized with triphenylamine (TPA) as the core, diketopyrrolopyrrole (DPP) as the arm and bithiophene as end-groups. The compound shows broad absorption, a low optical band gap of 1.61 eV and hole mobility of 1.99 × 10⁻⁴ cm² V⁻¹ s⁻¹. By blending with a [6,6]-phenyl-C₇₁-butyric acid methylester (PC₇₁BM) acceptor, an optimized power conversion efficiency (PCE) of 3.81% is achieved. The best efficiency was obtained via adding remarkably small percentages of solvent additives (0.1% v/v of 1,8-diiodooctane, DIO) to form well-defined structures and improved phase-separated film morphology in the bulk-heterojunction layer.