An alternative processing strategy for organic photovoltaic devices using a supercritical fluid

Jojo A. Amonoo, Emmanouil Glynos, X. Chelsea Chen, Peter F. Green

Research output: Contribution to journalArticlepeer-review

19 Scopus citations

Abstract

We propose a sustainable low temperature alternative, using supercritical carbon dioxide (scCO 2), to the conventional high temperature thermal annealing protocol for processing poly(3-hexylthiophene) (P3HT)/phenyl-C61- butyric acid methyl ester (PC 61BM) organic photovoltaic devices. This new strategy enabled the fabrication of devices that exhibited comparable, and often better, short circuit currents, J SC's, and efficiencies than those prepared using the conventional heat treatment protocol. While the fill factors (FF) of devices processed using either of the prorocols were comparable, the best performing scCO 2 processed devices provided the largest J SC's. With the use of energy-filtered transmission electron microscopy (EFTEM), and electron energy loss spectroscopy (EELS), we show that the supercritical solvent protocol enabled the formation of similar macro- and nanoscale morphology as the heat treatment protocol. The active materials in the devices with the best efficiencies possessed purer P3HT and PC 61BM phases, as shown by EFTEM/EELS. UV-vis measurements, moreover, corroborated this observation, revealing a higher average degree of packing and order of P3HT chains throughout the films. Conductive- and photoconductive-atomic force microscopy (cAFM and pcAFM) revealed that the higher efficiency devices possessed larger fractions of photoactive regions throughout the active material. The variations in photoconductivity are associated with changes in the local composition throughout the active material.

Original languageEnglish
Pages (from-to)20708-20716
Number of pages9
JournalJournal of Physical Chemistry C
Volume116
Issue number39
DOIs
StatePublished - Oct 4 2012
Externally publishedYes

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