An A-D-A′-D-A type small molecule acceptor with a broad absorption spectrum for organic solar cellsElectronic supplementary information (ESI) available: Synthesis details, 1H, 13C NMR, MALDI-TOF MS, TGA and DSC measurements, DFT calculations, device fabrication and measurement conditions, charge mobility measurement, and OSC device characterizations. See DOI: 10.1039/c7cc08497h

• Main Authors: Miao, Junhui, Meng, Bin, Liu, Jun, Wang, Lixiang
• Format: Article
• Language: English
• ISSN: 1359-7345; 1364-548X
• DOI: 10.1039/c7cc08497h

Organic molecules with wide absorption spectra exhibit great sunlight harvesting capability and are critically important for solar cell applications. In this manuscript, we develop an A-D-A′-D-A type small molecule acceptor (IID-IC) using isoindigo (IID) as the electron-deficient core unit (A′), thiophene as the electron-rich bridging units (D) and 2-(3-oxo-2,3-dihydroinden-1-ylidene)malononitrile (IC) as the electron-deficient endcapping groups (A). IID-IC shows a wide absorption spectrum with the full width at half maximum (FWHM) of 190 nm, which is almost twice that of a typical A-D-A type molecule acceptor. The wide absorption spectrum of IID-IC is possibly due to the partially suppressed intramolecular charge transfer effect with the additional electron-deficient core unit. An organic solar cell (OSC) device based on IID-IC exhibits the power conversion efficiency of 2.82% with broad photoresponse from 320 nm to 780 nm. The use of an A-D-A′-D-A strategy to develop small molecule acceptors with broad absorption spectra through suppressing the intramolecular charge transfer effect is studied.