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Title: Molecular engineering to improve carrier lifetimes for organic photovoltaic devices with thick active layers

The morphology of the bulk heterojunction absorber layer in an organic photovoltaic (OPV) device has a profound effect on the electrical properties and efficiency of the device. Previous work has consistently demonstrated that the solubilizing side-chains of the donor material affect these properties and device performance in a non-trivial way. Here, using Time-Resolved Microwave Conductivity (TRMC), we show by direct measurements of carrier lifetimes that the choice of side chains can also make a substantial difference in photocarrier dynamics. We have previously demonstrated a correlation between peak photoconductance measured by TRMC and device efficiencies; here, we demonstrate that TRMC photocarrier dynamics have an important bearing on device performance in a case study of devices made from donor materials with linear vs. branched side-chains and with variable active layer thicknesses. We use Grazing-Incidence Wide Angle X-ray Scattering to elucidate the cause of the different carrier lifetimes as a function of different aggregation behavior in the polymers. Consequently, the results help establish TRMC as a technique for screening OPV donor materials whose devices maintain performance in thick active layers (>250 nm) designed to improve light harvesting, film reproducibility, and ease of processing.
ORCiD logo [1] ;  [1] ;  [1] ;  [2] ;  [3] ;  [1] ;  [1]
  1. National Renewable Energy Lab. (NREL), Golden, CO (United States)
  2. Univ. of Santa Cruz, Santa Cruz, CA (United States)
  3. SLAC National Accelerator Lab., Menlo Park, CA (United States)
Publication Date:
Report Number(s):
Journal ID: ISSN 1566-1199
Grant/Contract Number:
AC36-08GO28308; AC36-08-GO28038; AC02-76SF00515; AC36-08GO28038
Accepted Manuscript
Journal Name:
Organic Electronics
Additional Journal Information:
Journal Volume: 47; Journal Issue: C; Journal ID: ISSN 1566-1199
Research Org:
National Renewable Energy Lab. (NREL), Golden, CO (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
14 SOLAR ENERGY; 42 ENGINEERING; time-resolved microwave conductivity; organic photovoltaics; x-ray diffraction; carrier lifetime; layer thickness
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1374535; OSTI ID: 1396380