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Title: On the Origin of Charge Generation in Hybrid TiOx/Conjugated Polymer Photovoltaic Devices

Abstract

Hybrid films of donor/acceptor conjugated polymer/metal oxides are considered promising materials for low-cost, solution-processed solar cells. Because device performances depend on the nanoscale film morphologies, most attention and extensive efforts have been invested in improving the nanofabrication of hybrid films. Nevertheless, the reported conjugated polymer/metal oxide device efficiencies are still far poorer than those of all-organic and solid-state dye-sensitized metal oxide solar cells. To decouple the effect of insufficient morphology control from other generic photocurrent-limiting processes, we study the photocurrent generation at conjugated polymer-metal oxide interfaces in self-organized, highly ordered, and uniform hybrid nanostructures. A combination of small-angle X-ray scattering, high-resolution transmission electron microscopy (TEM), and energy-filtered TEM confirms the structure and composition of the highly ordered, high interfacial area hybrid cubic mesostructured films prepared by the coassembly of a titania precursor species, a water-soluble polythiophene derivative, and a block copolymer surfactant. Contactless time-resolved microwave photoconductivity (TRMC) measurements show a moderate 2-fold increase in the photoconductivity of the highly ordered TiO{sub x}/conjugated polymer mesostructured film compared to that of a pristine film of the same polymer, indicating inefficient exciton dissociation at the oxide/polymer interface. Furthermore, strong correlation between the TRMC results and the device performance reveals that most of themore » photogenerated carriers in the conjugated polymer/TiO{sub x} photovoltaic device originate from exciton dissociation in the polymer bulk, followed by electron transfer from the polymer to the metal oxide, and not at the interface. Therefore, the photovoltaic devices utilizing the highly ordered conjugated polymer/metal oxide mesostructured films are not primarily limited by insufficient morphology control but rather by the inefficient process of exciton dissociation in the polymer. This observation is in agreement with the low photocurrent densities generally observed in photovoltaic devices comprising conjugated polymer/metal oxide active layers.« less

Authors:
; ; ;
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Solar Energy Technologies Office (EE-4S)
OSTI Identifier:
1045717
Report Number(s):
NREL/JA-5900-52900
Journal ID: ISSN 1932-7447; TRN: US201215%%102
DOE Contract Number:  
AC36-08GO28308
Resource Type:
Journal Article
Journal Name:
Journal of Physical Chemistry. C
Additional Journal Information:
Journal Volume: 116; Journal Issue: 2; Journal ID: ISSN 1932-7447
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 36 MATERIALS SCIENCE; 37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; COPOLYMERS; DISSOCIATION; ELECTRON TRANSFER; EXCITONS; MORPHOLOGY; NANOSTRUCTURES; ORIGIN; OXIDES; PERFORMANCE; PHOTOCONDUCTIVITY; PHOTOCURRENTS; POLYMERS; PRECURSOR; SCATTERING; SOLAR CELLS; TRANSMISSION ELECTRON MICROSCOPY; solar cells; hybrid films; photovoltaic; PV; polymer

Citation Formats

Segal-Peretz, Tamar, Leman, Olga, Nardes, Alexandre M., and Frey, Gitti L. On the Origin of Charge Generation in Hybrid TiOx/Conjugated Polymer Photovoltaic Devices. United States: N. p., 2012. Web. doi:10.1021/jp209016z.
Segal-Peretz, Tamar, Leman, Olga, Nardes, Alexandre M., & Frey, Gitti L. On the Origin of Charge Generation in Hybrid TiOx/Conjugated Polymer Photovoltaic Devices. United States. doi:10.1021/jp209016z.
Segal-Peretz, Tamar, Leman, Olga, Nardes, Alexandre M., and Frey, Gitti L. Thu . "On the Origin of Charge Generation in Hybrid TiOx/Conjugated Polymer Photovoltaic Devices". United States. doi:10.1021/jp209016z.
@article{osti_1045717,
title = {On the Origin of Charge Generation in Hybrid TiOx/Conjugated Polymer Photovoltaic Devices},
author = {Segal-Peretz, Tamar and Leman, Olga and Nardes, Alexandre M. and Frey, Gitti L.},
abstractNote = {Hybrid films of donor/acceptor conjugated polymer/metal oxides are considered promising materials for low-cost, solution-processed solar cells. Because device performances depend on the nanoscale film morphologies, most attention and extensive efforts have been invested in improving the nanofabrication of hybrid films. Nevertheless, the reported conjugated polymer/metal oxide device efficiencies are still far poorer than those of all-organic and solid-state dye-sensitized metal oxide solar cells. To decouple the effect of insufficient morphology control from other generic photocurrent-limiting processes, we study the photocurrent generation at conjugated polymer-metal oxide interfaces in self-organized, highly ordered, and uniform hybrid nanostructures. A combination of small-angle X-ray scattering, high-resolution transmission electron microscopy (TEM), and energy-filtered TEM confirms the structure and composition of the highly ordered, high interfacial area hybrid cubic mesostructured films prepared by the coassembly of a titania precursor species, a water-soluble polythiophene derivative, and a block copolymer surfactant. Contactless time-resolved microwave photoconductivity (TRMC) measurements show a moderate 2-fold increase in the photoconductivity of the highly ordered TiO{sub x}/conjugated polymer mesostructured film compared to that of a pristine film of the same polymer, indicating inefficient exciton dissociation at the oxide/polymer interface. Furthermore, strong correlation between the TRMC results and the device performance reveals that most of the photogenerated carriers in the conjugated polymer/TiO{sub x} photovoltaic device originate from exciton dissociation in the polymer bulk, followed by electron transfer from the polymer to the metal oxide, and not at the interface. Therefore, the photovoltaic devices utilizing the highly ordered conjugated polymer/metal oxide mesostructured films are not primarily limited by insufficient morphology control but rather by the inefficient process of exciton dissociation in the polymer. This observation is in agreement with the low photocurrent densities generally observed in photovoltaic devices comprising conjugated polymer/metal oxide active layers.},
doi = {10.1021/jp209016z},
journal = {Journal of Physical Chemistry. C},
issn = {1932-7447},
number = 2,
volume = 116,
place = {United States},
year = {2012},
month = {1}
}