Comparison of Photovoltaic Properties of Fused and Non-Fused Aromatic Spacers in DPP-based Small Molecules for Organic Solar Cells

Abstract

The optoelectronic properties of semiconductors are primarily governed by the type of conjugated unit in the molecular backbone. Especially, in utilization of the push-pull concept for designing low bandgap organic materials, selection of electron donating building block in the conjugated backbone requires special attention: one must consider electron donating capability, planarity, and solid state-self assembly of electron donating block. Herein we report the synthesis and characterization of diketopyrrolopyrrole (DPP)-based new organic molecules with various electron donation building blocks such as thiophene and phenylene, and their corresponding fused rings, thienothophene and naphthalene. The crystallinity and electrochemical properties of the new donor materials were measured by X-ray diffraction and cyclic voltammetry, respectively. Solar cell performances of devices with the donor materials were measured and systematically analyzed in terms of molecular structure with different electron donating building block.