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Title: Effects of humidity during formation of zinc oxide electron contact layers from a diethylzinc precursor solution

Abstract

Here, this work focuses on the role of humidity in the formation of ZnO thin films from a reactive diethylzinc precursor solution for use as the electron contact layer (ECL) in organic photovoltaic (OPV) devices. This method is well suited for flexible devices because the films are annealed at 120 °C, making the process compatible with polymer substrates. ZnO films were prepared by spin coating and annealing at different relative humidity (RH) levels. It is found that RH during coating and annealing affects the chemical and physical properties of the ZnO films. Using x-ray photoelectron spectroscopy it is found that increasing RH during the formation steps produces a more stoichiometric oxide and a higher Zn/O ratio. Spectroscopic ellipsometry data shows a small decrease in the optical band gap with increased humidity, consistent with a more stoichiometric oxide. Kelvin probe measurements show that increased RH during formation results in a larger work function (i.e. further from vacuum). Consistent with these data, but counter to what might be expected, when these ZnO films are used as ECLs in OPV devices those with ZnO ECLs processed in low RH (less stoichiometric) had higher power conversion efficiency than those with high-RH processed ZnO duemore » to improved open-circuit voltage. The increase in open-circuit voltage with decreasing humidity was observed with two different donor polymers and fullerene acceptors, which shows the trend is due to changes in ZnO. The observed changes in open-circuit voltage follow the same trend as the ZnO work function indicating that the increase in open-circuit voltage with decreasing humidity is the result of improved energetics at the interface between the bulk-heterojunction and the ZnO layer due to a vacuum level shift.« less

Authors:
 [1];  [1];  [2];  [3];  [1];  [4]
  1. National Renewable Energy Lab. (NREL), Golden, CO (United States)
  2. National Renewable Energy Lab. (NREL), Golden, CO (United States); Univ. of Colorado, Boulder, CO (United States); Friedrich-Alexander Univ., Erlangen (Germany)
  3. Friedrich-Alexander Univ., Erlangen (Germany)
  4. SolarWindow Technologies, Inc., Columbia, MD (United States)
Publication Date:
Research Org.:
National Renewable Energy Laboratory (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE NREL-Solar Window Technologies, Inc. Cooperative Research and Development Agreement (CRADA); USDOE
OSTI Identifier:
1237035
Alternate Identifier(s):
OSTI ID: 1341200
Report Number(s):
NREL/JA-5900-64538
Journal ID: ISSN 1566-1199
Grant/Contract Number:  
AC36-08GO28308
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Organic Electronics
Additional Journal Information:
Journal Volume: 31; Related Information: Organic Electronics; Journal ID: ISSN 1566-1199
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 36 MATERIALS SCIENCE; organic photovoltaics; zinc oxide; processing; humidity; contact layer

Citation Formats

Mauger, Scott A., Steirer, K. Xerxes, Boe, Jonas, Ostrowski, David P., Olson, Dana C., and Hammond, Scott R. Effects of humidity during formation of zinc oxide electron contact layers from a diethylzinc precursor solution. United States: N. p., 2016. Web. doi:10.1016/j.orgel.2016.01.012.
Mauger, Scott A., Steirer, K. Xerxes, Boe, Jonas, Ostrowski, David P., Olson, Dana C., & Hammond, Scott R. Effects of humidity during formation of zinc oxide electron contact layers from a diethylzinc precursor solution. United States. https://doi.org/10.1016/j.orgel.2016.01.012
Mauger, Scott A., Steirer, K. Xerxes, Boe, Jonas, Ostrowski, David P., Olson, Dana C., and Hammond, Scott R. 2016. "Effects of humidity during formation of zinc oxide electron contact layers from a diethylzinc precursor solution". United States. https://doi.org/10.1016/j.orgel.2016.01.012. https://www.osti.gov/servlets/purl/1237035.
@article{osti_1237035,
title = {Effects of humidity during formation of zinc oxide electron contact layers from a diethylzinc precursor solution},
author = {Mauger, Scott A. and Steirer, K. Xerxes and Boe, Jonas and Ostrowski, David P. and Olson, Dana C. and Hammond, Scott R.},
abstractNote = {Here, this work focuses on the role of humidity in the formation of ZnO thin films from a reactive diethylzinc precursor solution for use as the electron contact layer (ECL) in organic photovoltaic (OPV) devices. This method is well suited for flexible devices because the films are annealed at 120 °C, making the process compatible with polymer substrates. ZnO films were prepared by spin coating and annealing at different relative humidity (RH) levels. It is found that RH during coating and annealing affects the chemical and physical properties of the ZnO films. Using x-ray photoelectron spectroscopy it is found that increasing RH during the formation steps produces a more stoichiometric oxide and a higher Zn/O ratio. Spectroscopic ellipsometry data shows a small decrease in the optical band gap with increased humidity, consistent with a more stoichiometric oxide. Kelvin probe measurements show that increased RH during formation results in a larger work function (i.e. further from vacuum). Consistent with these data, but counter to what might be expected, when these ZnO films are used as ECLs in OPV devices those with ZnO ECLs processed in low RH (less stoichiometric) had higher power conversion efficiency than those with high-RH processed ZnO due to improved open-circuit voltage. The increase in open-circuit voltage with decreasing humidity was observed with two different donor polymers and fullerene acceptors, which shows the trend is due to changes in ZnO. The observed changes in open-circuit voltage follow the same trend as the ZnO work function indicating that the increase in open-circuit voltage with decreasing humidity is the result of improved energetics at the interface between the bulk-heterojunction and the ZnO layer due to a vacuum level shift.},
doi = {10.1016/j.orgel.2016.01.012},
url = {https://www.osti.gov/biblio/1237035}, journal = {Organic Electronics},
issn = {1566-1199},
number = ,
volume = 31,
place = {United States},
year = {Tue Jan 19 00:00:00 EST 2016},
month = {Tue Jan 19 00:00:00 EST 2016}
}

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Cited by: 3 works
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Works referenced in this record:

Probing Charge Carrier Density in a Layer of Photodoped ZnO Nanoparticles by Spectroscopic Ellipsometry
journal, August 2010


Evolution of microstructure and related optical properties of ZnO grown by atomic layer deposition
journal, January 2013


The structural and optical properties of ZnO thin films prepared at different RF sputtering power
journal, July 2013


Parameterization of the optical functions of amorphous materials in the interband region
journal, July 1996


Levelised cost of electricity for organic photovoltaics
journal, February 2015


Solar cell efficiency tables (version 44): Solar cell efficiency tables
journal, June 2014


Influence of the hole-transport layer on the initial behavior and lifetime of inverted organic photovoltaics
journal, May 2011


Effect of ZnO layer on characteristics of conducting polymer/C60photovoltaic cell
journal, February 2004


New Architecture for High-Efficiency Polymer Photovoltaic Cells Using Solution-Based Titanium Oxide as an Optical Spacer
journal, March 2006


Air-stable inverted flexible polymer solar cells using zinc oxide nanoparticles as an electron selective layer
journal, June 2008


Inverted bulk-heterojunction organic photovoltaic device using a solution-derived ZnO underlayer
journal, October 2006


Hybrid Solar Cells Using a Zinc Oxide Precursor and a Conjugated Polymer
journal, October 2005


Stability of inverted organic solar cells with ZnO contact layers deposited from precursor solutions
journal, January 2015


Inverted Polymer Solar Cells Integrated with a Low-Temperature-Annealed Sol-Gel-Derived ZnO Film as an Electron Transport Layer
journal, February 2011


Efficient inverted bulk-heterojunction solar cells from low-temperature processing of amorphous ZnO buffer layers
journal, January 2014


Mechanisms of the Reactions of Diethylzinc with Isopropanol and Water
journal, May 1963


ZnO layers for opto-electronic applications from solution-based and low-temperature processing of an organometallic precursor
journal, January 2012


ALD grown zinc oxide with controllable electrical properties
journal, June 2012


Effects of the Morphology of a ZnO Buffer Layer on the Photovoltaic Performance of Inverted Polymer Solar Cells
journal, March 2012


Characterization of phosphonic acid binding to zinc oxide
journal, January 2011


Probing Charge Carrier Density in a Layer of Photodoped ZnO Nanoparticles by Spectroscopic Ellipsometry
journal, August 2010


Parameterization of the optical functions of amorphous materials in the interband region
journal, July 1996


The structural and optical properties of ZnO thin films prepared at different RF sputtering power
journal, July 2013


Evolution of microstructure and related optical properties of ZnO grown by atomic layer deposition
journal, January 2013


Solution Processed ZnO Hybrid Nanocomposite with Tailored Work Function for Improved Electron Transport Layer in Organic Photovoltaic Devices
journal, September 2013


Conjugated Phosphonic Acid Modified Zinc Oxide Electron Transport Layers for Improved Performance in Organic Solar Cells
journal, October 2014


Tuning zinc oxide/organic energy level alignment using mixed triethoxysilane monolayers
journal, January 2013


Energy-Level Alignment at Organic/Metal and Organic/Organic Interfaces
journal, April 2009


Cathode dependence of the open-circuit voltage of polymer:fullerene bulk heterojunction solar cells
journal, November 2003


Universal energy-level alignment of molecules on metal oxides
journal, November 2011


Efficient Methano[70]fullerene/MDMO‐PPV Bulk Heterojunction Photovoltaic Cells
journal, July 2003


Indene−C60 Bisadduct: A New Acceptor for High-Performance Polymer Solar Cells
journal, February 2010


Selective Interlayers and Contacts in Organic Photovoltaic Cells
journal, May 2011