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Photovoltaic Performance of Ultrasmall PbSe Quantum Dots

Ma, Wanli and Swisher, Sarah L. and Ewers, Trevor and Engel, Jesse and Ferry, Vivian E. and Atwater, Harry A. and Alivisatos, A. Paul (2011) Photovoltaic Performance of Ultrasmall PbSe Quantum Dots. ACS Nano, 5 (10). pp. 8140-8147. ISSN 1936-0851. doi:10.1021/nn202786g.

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We investigated the effect of PbSe quantum dot size on the performance of Schottky solar cells made in an ITO/PEDOT/PbSe/aluminum structure, varying the PbSe nanoparticle diameter from 1 to 3 nm. In this highly confined regime, we find that the larger particle bandgap can lead to higher open-circuit voltages (~0.6 V), and thus an increase in overall efficiency compared to previously reported devices of this structure. To carry out this study, we modified existing synthesis methods to obtain ultrasmall PbSe nanocrystals with diameters as small as 1 nm, where the nanocrystal size is controlled by adjusting the growth temperature. As expected, we find that photocurrent decreases with size due to reduced absorption and increased recombination, but we also find that the open-circuit voltage begins to decrease for particles with diameters smaller than 2 nm, most likely due to reduced collection efficiency. Owing to this effect, we find peak performance for devices made with PbSe dots with a first exciton energy of ~1.6 eV (2.3 nm diameter), with a typical efficiency of 3.5%, and a champion device efficiency of 4.57%. Comparing the external quantum efficiency of our devices to an optical model reveals that the photocurrent is also strongly affected by the coherent interference in the thin film due to Fabry-Pérot cavity modes within the PbSe layer. Our results demonstrate that even in this simple device architecture, fine-tuning of the nanoparticle size can lead to substantial improvements in efficiency.

Item Type:Article
Related URLs:
URLURL TypeDescription
Atwater, Harry A.0000-0001-9435-0201
Alivisatos, A. Paul0000-0001-6895-9048
Additional Information:© 2011 American Chemical Society. Received for review July 22, 2011, and accepted September 22, 2011. Publication Date (Web): September 22, 2011. We gratefully acknowledge D. Ghosh, D. Britt, M. L. Tang, and M. Lucas for helpful discussions. This work was supported by the DOE 'Light-Material Interactions in Energy Conversion' Energy Frontier Research Center under Grant DE-SC0001293. S.L.S and J.E. were supported by National Science Foundation Graduate Research Fellowships.
Funding AgencyGrant Number
Department of Energy (DOE)DE-SC0001293
NSF Graduate Research FellowshipUNSPECIFIED
Subject Keywords:PbSe; quantum dot; solar cell; photovoltaic; quantum size effect
Issue or Number:10
Record Number:CaltechAUTHORS:20111122-113441418
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Official Citation: Photovoltaic Performance of Ultrasmall PbSe Quantum Dots Wanli Ma, Sarah L. Swisher, Trevor Ewers, Jesse Engel, Vivian E. Ferry, Harry A. Atwater, and A. Paul Alivisatos ACS Nano 2011 5 (10), 8140-8147
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:27917
Deposited By: Ruth Sustaita
Deposited On:22 Nov 2011 21:08
Last Modified:09 Nov 2021 16:52

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