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Title: Long Carrier Lifetimes in Large-Grain Polycrystalline CdTe Without CdCl2

Abstract

For decades, polycrystalline CdTe thin films for solar applications have been restricted to grain sizes of microns or less whereas other semiconductors such as silicon and perovskites have produced devices with grains ranging from less than a micron to more than 1 mm. Because the lifetimes in as-deposited polycrystalline CdTe films are typically limited to less than a few hundred picoseconds, a CdCl2 treatment is generally used to improve the lifetime; but this treatment may limit the achievable hole density by compensation. Here, we establish methods to produce CdTe films with grain sizes ranging from hundreds of nanometers to several hundred microns by close-spaced sublimation at industrial manufacturing growth rates. Two-photon excitation photoluminescence spectroscopy shows a positive correlation of lifetime with grain size. Large-grain, as-deposited CdTe exhibits lifetimes exceeding 10 ns without Cl, S, O, or Cu. This uncompensated material allows dopants such as P to achieve a hole density of 1016 cm-3, which is an order of magnitude higher than standard CdCl2-treated devices, without compromising the lifetime.

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:
1266707
Report Number(s):
NREL/JA-5900-66346
Journal ID: ISSN 0003-6951
DOE Contract Number:
AC36-08GO28308
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 108; Journal Issue: 26
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 36 MATERIALS SCIENCE; polycrystalline CdTe; TRPL

Citation Formats

Jensen, Soren A., Burst, James M., Duenow, Joel N., Guthrey, Harvey L., Moseley, John, Moutinho, Helio R., Johnston, Steve W., Kanevce, Ana, Al-Jassim, Mowafak M., and Metzger, Wyatt K. Long Carrier Lifetimes in Large-Grain Polycrystalline CdTe Without CdCl2. United States: N. p., 2016. Web. doi:10.1063/1.4954904.
Jensen, Soren A., Burst, James M., Duenow, Joel N., Guthrey, Harvey L., Moseley, John, Moutinho, Helio R., Johnston, Steve W., Kanevce, Ana, Al-Jassim, Mowafak M., & Metzger, Wyatt K. Long Carrier Lifetimes in Large-Grain Polycrystalline CdTe Without CdCl2. United States. doi:10.1063/1.4954904.
Jensen, Soren A., Burst, James M., Duenow, Joel N., Guthrey, Harvey L., Moseley, John, Moutinho, Helio R., Johnston, Steve W., Kanevce, Ana, Al-Jassim, Mowafak M., and Metzger, Wyatt K. Mon . "Long Carrier Lifetimes in Large-Grain Polycrystalline CdTe Without CdCl2". United States. doi:10.1063/1.4954904.
@article{osti_1266707,
title = {Long Carrier Lifetimes in Large-Grain Polycrystalline CdTe Without CdCl2},
author = {Jensen, Soren A. and Burst, James M. and Duenow, Joel N. and Guthrey, Harvey L. and Moseley, John and Moutinho, Helio R. and Johnston, Steve W. and Kanevce, Ana and Al-Jassim, Mowafak M. and Metzger, Wyatt K.},
abstractNote = {For decades, polycrystalline CdTe thin films for solar applications have been restricted to grain sizes of microns or less whereas other semiconductors such as silicon and perovskites have produced devices with grains ranging from less than a micron to more than 1 mm. Because the lifetimes in as-deposited polycrystalline CdTe films are typically limited to less than a few hundred picoseconds, a CdCl2 treatment is generally used to improve the lifetime; but this treatment may limit the achievable hole density by compensation. Here, we establish methods to produce CdTe films with grain sizes ranging from hundreds of nanometers to several hundred microns by close-spaced sublimation at industrial manufacturing growth rates. Two-photon excitation photoluminescence spectroscopy shows a positive correlation of lifetime with grain size. Large-grain, as-deposited CdTe exhibits lifetimes exceeding 10 ns without Cl, S, O, or Cu. This uncompensated material allows dopants such as P to achieve a hole density of 1016 cm-3, which is an order of magnitude higher than standard CdCl2-treated devices, without compromising the lifetime.},
doi = {10.1063/1.4954904},
journal = {Applied Physics Letters},
number = 26,
volume = 108,
place = {United States},
year = {Mon Jun 27 00:00:00 EDT 2016},
month = {Mon Jun 27 00:00:00 EDT 2016}
}
  • Cited by 6
  • For decades, polycrystalline CdTe thin films for solar applications have been restricted to grain sizes of microns or less whereas other semiconductors such as silicon and perovskites have produced devices with grains ranging from less than a micron to more than 1 mm. Because the lifetimes in as-deposited polycrystalline CdTe films are typically limited to less than a few hundred picoseconds, a CdCl{sub 2} treatment is generally used to improve the lifetime; but this treatment may limit the achievable hole density by compensation. Here, we establish methods to produce CdTe films with grain sizes ranging from hundreds of nanometers to severalmore » hundred microns by close-spaced sublimation at industrial manufacturing growth rates. Two-photon excitation photoluminescence spectroscopy shows a positive correlation of lifetime with grain size. Large-grain, as-deposited CdTe exhibits lifetimes exceeding 10 ns without Cl, S, O, or Cu. This uncompensated material allows dopants such as P to achieve a hole density of 10{sup 16 }cm{sup −3}, which is an order of magnitude higher than standard CdCl{sub 2}-treated devices, without compromising the lifetime.« less
  • Time-resolved photoluminescence measurements on glass/SnO{sub 2}/CdTe and glass/SnO{sub 2}/CdTe/CdS structures indicate that the CdCl{sub 2} process, without any S present, significantly reduces recombination. However, S diffusion is required for lifetimes comparable to those observed in high-efficiency solar cells. Low-temperature photoluminescence, cathodoluminescence, and scanning electron images indicate how defect chemistry, grain-boundary passivation, and morphology are affected by S diffusion and the CdCl{sub 2} treatment.
  • The interface recombination velocities of CdTe/Mg{sub x}Cd{sub 1−x}Te double heterostructure (DH) samples with different CdTe layer thicknesses and Mg compositions are studied using time-resolved photoluminescence measurements. A lowest interface recombination velocity of 30 ± 10 cm/s has been measured for the CdTe/Mg{sub 0.46}Cd{sub 0.54}Te interface, and a longest carrier lifetime of 0.83 μs has been observed for the studied DHs. These values are very close to the best reported numbers for GaAs/AlGaAs DHs. The impact of carrier escape through thermionic emission over the MgCdTe barrier on the recombination process in the DHs is also studied.