Phthalimide-Based π-Conjugated Small Molecules with Tailored Electronic Energy Levels for Use as Acceptors in Organic Solar Cells

Authors

Arthur D. Hendsbee, Dalhousie University
Seth M. McAfee, Dalhousie University
Jon-Paul Sun, Dalhousie University
Theresa M. McCormick, Portland State UniversityFollow
Ian G. Hill, Dalhousie University
Gregory C. Welch, University of Calgary

Published In

Journal of Materials Chemistry C

Document Type

Article

Publication Date

2015

Subjects

Solar energy conversion, Solar energy -- Materials, Solar cells

Abstract

The design, synthesis, and characterization of seven phthalimide-based organic π-conjugated small molecules are reported. The new materials are based on a phthalimide–thiophene–CORE–thiophene–phthalimide architecture. The CORE units utilized were phthalimide (M2), diketopyrrolopyrrole (M3), isoindigo (M4), naphthalene diimide (M5), perylene diimide (M6), and difluorobenzothiadiazole (M7); they were specifically selected to progressively increase the electron affinity of the resulting compound. A small molecule with no core (M1) was synthesized for comparison. Each material was synthesized through optimized direct heteroarylation cross-coupling procedures using bench top solvents in air. Combinations of UV-visible spectroscopy (UV-vis), cyclic voltammetry (CV), differential scanning calorimetry (DSC), ultraviolet photoelectron spectroscopy (UPS) and density functional theory (DFT) were used to characterize each material. The use of various core acceptor building blocks with differing electron affinities resulted in the series M1–M7 having a range of energetically deep LUMO levels and a range of HOMO–LUMO gap energies. Meanwhile, the melting and crystallization temperatures of the molecules M1–M7 were also found to vary according to the change in central acceptor unit. Compounds M1–M7 were employed as acceptors in combination with either the polymeric donor P3HT or small molecule donor DTS(FBTTh₂)₂ to understand how the LUMO levels of each acceptor influences the open circuit voltage (V_oc). It was found that, in general, V_oc was only weakly related to the offset between the HOMO energy level of the donor and LUMO level of the acceptor used, with a V_oc of up to 1.2 V being achieved for M1.

Description

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. Open Access

This journal is © The Royal Society of Chemistry 2015

DOI

10.1039/C5TC01877C

Persistent Identifier

http://archives.pdx.edu/ds/psu/16179

Citation Details

Arthur D. Hendsbee, Seth M. McAfee, Jon-Paul Sun, Theresa M. McCormick, Ian G. Hill and Gregory C. Welch (2015). Phthalimide-based π-conjugated small molecules with tailored electronic energy levels for use as acceptors in organic solar cells. Journal of Materials Chemistry C, 3 8904-8915.