Bourque, A.
, Engmann, S.
, Fuster, A.
, Snyder, C.
, Richter, L.
, Geraghty, P.
and Jones, D.
(2019),
Morphology of a thermally stable small molecule OPV blend comprising a liquid crystalline donor and fullerene acceptor, Journal of Materials Chemistry A, [online], https://doi.org/10.1039/c9ta01989h
(Accessed April 29, 2024)
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.
Morphology of a thermally stable small molecule OPV blend comprising a liquid crystalline donor and fullerene acceptor
Published
Author(s)
, , Allison Fuster, , , Paul B. Geraghty, David J. Jones
Abstract
Recently organic photovoltaic (OPV) devices comprising the small molecule liquid-crystalline donor, benzodithiophene-quaterthiophene-rhodanine (BQR), were demonstrated to achieve high performance when thermally processed, avoiding the need for slow-drying solvent additives or complex solvent vapor annealing post-processing. In this investigation we explore the impact of thermal processing on thin film blends of BQR and the fullerene acceptor PC71BM using differential scanning calorimetry (DSC), in situ grazing incidence X-ray scattering (GISAXS, GIWAXS), and photoluminescence spectroscopy (PL) to correlate thermal behavior with morphological changes and photoactivity. We develop a phase map of the crystalline and liquid crystalline transitions in BQR and the related high performing electron donor material, benzodithiophene-terthiophene-rhodanine (BTR), and are able to predict phase transitions using Flory-Huggins theory. Further DSC measurements demonstrate the superior thermal stability of PC71BM blends with BQR over blends with BTR. OPV devices with the BQR:PC71BM active layer were prepared using the blade-coated deposition technique and exhibit optimal device performance when annealed at 120 °C for 5 min. The characteristic acceptor/donor domain size in an as-cast BQR:PC71BM film, estimated from GISAXS, was about 60 nm which is sufficient for exciton separation. Domain purity was enhanced by annealing at temperatures above ≈ 80 °C. Annealing at temperatures above ≈ 120 C resulted in over-coarsening of the acceptor/donor-rich phases to domain sizes beyond 80 nm and reduced performance.Citation
Journal of Materials Chemistry A
Volume
7
Issue
27
Pub Type
Journals
Download Paper
Citation
Created June 4, 2019, Updated February 4, 2020