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Title: Modeling the Free Carrier Recombination Kinetics in PTB7:PCBM Organic Photovoltaics

Currently the exact recombination mechanism of free carriers in organic photovoltaic (OPV) devices is poorly understood. Often a reduced Langevin model is used to describe the decay behavior of electrons and holes. Here we propose a novel, simple kinetic model that accurately describes the decay behavior of free carriers in the PTB7:PCBM organic photovoltaic blend. In order to accurately describe the recombination behavior of free carriers as measured by time-resolved microwave conductivity (TRMC), this model needs to only take into account free and trapped holes in the polymer, and free electrons in the fullerene. The model is consistent for different PTB7:PCBM blend ratios and spans a light intensity range of over 3 orders of magnitude. Furthermore, the model demonstrates that dark carriers exist in the polymer and interact with photoinduced charge carriers, and that the trapping and detrapping rates of the holes are of high importance to the overall carrier lifetime.
Authors:
 [1] ;  [1] ;  [1] ;  [1] ;  [1]
  1. National Renewable Energy Lab. (NREL), Golden, CO (United States). Chemistry and Nanoscience Center
Publication Date:
OSTI Identifier:
1331480
Report Number(s):
NREL/JA-5900-66893
Journal ID: ISSN 1932-7447
Grant/Contract Number:
AC36-08GO28308
Type:
Accepted Manuscript
Journal Name:
Journal of Physical Chemistry. C
Additional Journal Information:
Journal Volume: 120; Journal Issue: 43; Journal ID: ISSN 1932-7447
Publisher:
American Chemical Society
Research Org:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE)
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 36 MATERIALS SCIENCE; organic photovoltaics; kinetic model; recombination; time-resolved microwave conductivity