skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Inorganic-ligand exchanging time effect in PbS quantum dot solar cell

Abstract

We investigate time-dependent inorganic ligand exchanging effect and photovoltaic performance of lead sulfide (PbS) nanocrystal films. With optimal processing time, volume shrinkage induced by residual oleic acid of the PbS colloidal quantum dot (CQD) was minimized and a crack-free film was obtained with improved flatness. Furthermore, sufficient surface passivation significantly increased the packing density by replacing from long oleic acid to a short iodide molecule. It thus facilities exciton dissociation via enhanced charge carrier transport in PbS CQD films, resulting in the improved power conversion efficiency from 3.39% to 6.62%. We also found that excess iodine ions on the PbS surface rather hinder high photovoltaic performance of the CQD solar cell.

Authors:
; ; ; ; ;  [1];  [2]
  1. Department of Engineering Science, University of Oxford, Parks Road, Oxford OX1 3PJ (United Kingdom)
  2. Department of Engineering, University of Cambridge, 9 JJ Thomson Avenue, Cambridge CB3 0FA (United Kingdom)
Publication Date:
OSTI Identifier:
22594363
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 109; Journal Issue: 6; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; CHARGE CARRIERS; CRACKS; FILMS; IODIDES; IODINE; IODINE IONS; ION EXCHANGE; LEAD SULFIDES; LIGANDS; MOLECULES; OLEIC ACID; PHOTOVOLTAIC EFFECT; QUANTUM DOTS; SOLAR CELLS; SURFACES; TIME DEPENDENCE

Citation Formats

Kim, Byung-Sung, Hong, John, Hou, Bo, Cho, Yuljae, Sohn, Jung Inn, E-mail: junginn.sohn@eng.ox.ac.uk, E-mail: seungnam.cha@eng.ox.ac.uk, Cha, SeungNam, E-mail: junginn.sohn@eng.ox.ac.uk, E-mail: seungnam.cha@eng.ox.ac.uk, and Kim, Jong Min. Inorganic-ligand exchanging time effect in PbS quantum dot solar cell. United States: N. p., 2016. Web. doi:10.1063/1.4960645.
Kim, Byung-Sung, Hong, John, Hou, Bo, Cho, Yuljae, Sohn, Jung Inn, E-mail: junginn.sohn@eng.ox.ac.uk, E-mail: seungnam.cha@eng.ox.ac.uk, Cha, SeungNam, E-mail: junginn.sohn@eng.ox.ac.uk, E-mail: seungnam.cha@eng.ox.ac.uk, & Kim, Jong Min. Inorganic-ligand exchanging time effect in PbS quantum dot solar cell. United States. doi:10.1063/1.4960645.
Kim, Byung-Sung, Hong, John, Hou, Bo, Cho, Yuljae, Sohn, Jung Inn, E-mail: junginn.sohn@eng.ox.ac.uk, E-mail: seungnam.cha@eng.ox.ac.uk, Cha, SeungNam, E-mail: junginn.sohn@eng.ox.ac.uk, E-mail: seungnam.cha@eng.ox.ac.uk, and Kim, Jong Min. Mon . "Inorganic-ligand exchanging time effect in PbS quantum dot solar cell". United States. doi:10.1063/1.4960645.
@article{osti_22594363,
title = {Inorganic-ligand exchanging time effect in PbS quantum dot solar cell},
author = {Kim, Byung-Sung and Hong, John and Hou, Bo and Cho, Yuljae and Sohn, Jung Inn, E-mail: junginn.sohn@eng.ox.ac.uk, E-mail: seungnam.cha@eng.ox.ac.uk and Cha, SeungNam, E-mail: junginn.sohn@eng.ox.ac.uk, E-mail: seungnam.cha@eng.ox.ac.uk and Kim, Jong Min},
abstractNote = {We investigate time-dependent inorganic ligand exchanging effect and photovoltaic performance of lead sulfide (PbS) nanocrystal films. With optimal processing time, volume shrinkage induced by residual oleic acid of the PbS colloidal quantum dot (CQD) was minimized and a crack-free film was obtained with improved flatness. Furthermore, sufficient surface passivation significantly increased the packing density by replacing from long oleic acid to a short iodide molecule. It thus facilities exciton dissociation via enhanced charge carrier transport in PbS CQD films, resulting in the improved power conversion efficiency from 3.39% to 6.62%. We also found that excess iodine ions on the PbS surface rather hinder high photovoltaic performance of the CQD solar cell.},
doi = {10.1063/1.4960645},
journal = {Applied Physics Letters},
number = 6,
volume = 109,
place = {United States},
year = {Mon Aug 08 00:00:00 EDT 2016},
month = {Mon Aug 08 00:00:00 EDT 2016}
}
  • We provide the first NREL-certified efficiency measurement on an all-inorganic, solution-processed, nanocrystal solar cell. The 3% efficient device is composed of ZnO nanocrystals and 1.3 eV PbS quantum dots with gold as the top contact. This configuration yields a stable device, retaining 95% of the starting efficiency after a 1000-hour light soak in air without encapsulation.
  • The current-voltage (J-V) characteristics of ZnO/PbS quantum dot (QD) solar cells show a QD size-dependent behavior resulting from a Schottky junction that forms at the back metal electrode opposing the desirable diode formed between the ZnO and PbS QD layers. We study a QD size-dependent roll-over effect that refers to the saturation of photocurrent in forward bias and crossover effect which occurs when the light and dark J-V curves intersect. We model the J-V characteristics with a main diode formed between the n-type ZnO nanocrystal (NC) layer and p-type PbS QD layer in series with a leaky Schottky-diode formed betweenmore » PbS QD layer and metal contact. We show how the characteristics of the two diodes depend on QD size, metal work function, and PbS QD layer thickness, and we discuss how the presence of the back diode complicates finding an optimal layer thickness. Finally, we present Kelvin probe measurements to determine the Fermi level of the QD layers and discuss band alignment, Fermi-level pinning, and the V oc within these devices.« less
  • The current-voltage (J-V) characteristics of ZnO/PbS quantum dot (QD) solar cells show a QD size-dependent behavior resulting from a Schottky junction that forms at the back metal electrode opposing the desirable diode formed between the ZnO and PbS QD layers. Here, we study a QD size-dependent roll-over effect that refers to the saturation of photocurrent in forward bias and crossover effect which occurs when the light and dark J-V curves intersect. Our model shows the J-V characteristics with a main diode formed between the n-type ZnO nanocrystal (NC) layer and p-type PbS QD layer in series with a leaky Schottky-diodemore » formed between PbS QD layer and metal contact. Moreover, we show how the characteristics of the two diodes depend on QD size, metal work function, and PbS QD layer thickness, and we discuss how the presence of the back diode complicates finding an optimal layer thickness. Finally, we present Kelvin probe measurements to determine the Fermi level of the QD layers and discuss band alignment, Fermi-level pinning, and the V oc within these devices.« less