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Issue 18, 2016
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Understanding the morphology of solution processed fullerene-free small molecule bulk heterojunction blends

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Abstract

Bulk-heterojunction (BHJ) molecular blends prepared from small molecules based on diketopyrrolopyrrole (DPP) and perylene-diimide (PDI) chromophores have been studied using optical absorption, cyclic voltammetry, photoluminescence quenching, X-ray diffraction, atomic force microscopy, and current–voltage measurements. The results provided useful insights into the use of DPP and PDI based molecules as donor–acceptor composites for organic photovoltaic (OPV) applications. Beside optoelectronic compatibility, the choice of active layer processing conditions is of key importance to improve the performance of BHJ solar cells. In this context, post-production treatments, viz. thermal and solvent vapour annealing, and the use of 1,8-diiodooctane as a solvent additive were employed to optimize the morphology of blend films. X-ray diffraction and atomic force microscopy indicated that the aforementioned processing strategies led to non-optimal composite morphologies with significantly large crystallites in comparison to exciton diffusion lengths. Although the open circuit voltage of the OPV devices was satisfactory (0.78 V), it was anticipated that the bulky domains hamper charge dissociation and transport, which resulted in low photovoltaic performance.

Graphical abstract: Understanding the morphology of solution processed fullerene-free small molecule bulk heterojunction blends

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Supplementary files

Article information


Submitted
24 Feb 2016
Accepted
30 Mar 2016
First published
31 Mar 2016

This article is Open Access

Phys. Chem. Chem. Phys., 2016,18, 12476-12485
Article type
Paper

Understanding the morphology of solution processed fullerene-free small molecule bulk heterojunction blends

A. Namepetra, E. Kitching, A. F. Eftaiha, I. G. Hill and G. C. Welch, Phys. Chem. Chem. Phys., 2016, 18, 12476
DOI: 10.1039/C6CP01269H

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