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Title: Light-induced degradation and metastable-state recovery with reaction kinetics modeling in boron-doped Czochralski silicon solar cells

Abstract

Solar cells fabricated from boron-doped p-type Czochralski silicon suffer from light-induced degradation that can lower the conversion efficiency by up to 10% relative. When solar cells are exposed to temperatures between 100 °C and 200 °C under illumination, regeneration, in which the minority carrier lifetime is gradually recovered, occurs after the initial light-induced degradation. We studied the light-induced degradation and regeneration process using carrier injection within a design chamber and observed open-circuit voltage trends at various sample temperatures. We proposed a cyclic reaction kinetics model to more precisely analyze the degradation and recovery phenomenon. Our model incorporated the reaction paths that were not counted in the original model between the three states (annealed, degradation, and regeneration). We calculated a rate constant for each reaction path based on the proposed model, extracted an activation energy for each reaction using these rate constants at various temperatures, and calculated activation energies of redegradation and the stabilization reaction.

Authors:
; ; ; ; ;  [1]; ;  [2];  [3]
  1. Department of Materials Science and Engineering, Korea University, Anam-dong, Seongbuk-gu, Seoul 136-701 (Korea, Republic of)
  2. Korea Institute of Energy Research, 152 Gajeong-ro, Yuseong-gu, Daejeon 305-343 (Korea, Republic of)
  3. KU-KIST Green School, Graduate School of Energy and Environment, Korea University, Anam-dong, Seongbuk-gu, Seoul 136-701 (Korea, Republic of)
Publication Date:
OSTI Identifier:
22310987
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 105; Journal Issue: 8; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ACTIVATION ENERGY; ANNEALING; BORON ADDITIONS; CARRIER LIFETIME; CARRIERS; COMPUTERIZED SIMULATION; DOPED MATERIALS; EFFICIENCY; ELECTRIC POTENTIAL; METASTABLE STATES; P-TYPE CONDUCTORS; REACTION KINETICS; REGENERATION; SILICON SOLAR CELLS; STABILIZATION; VISIBLE RADIATION

Citation Formats

Kim, Soo Min, Chun, Seungju, Bae, Suhyun, Park, Seungeun, Lee, Hae-seok, E-mail: lhseok@korea.ac.kr, Kim, Donghwan, E-mail: donghwan@korea.ac.kr, Kang, Min Gu, Song, Hee-eun, and Kang, Yoonmook, E-mail: ddang@korea.ac.kr. Light-induced degradation and metastable-state recovery with reaction kinetics modeling in boron-doped Czochralski silicon solar cells. United States: N. p., 2014. Web. doi:10.1063/1.4894289.
Kim, Soo Min, Chun, Seungju, Bae, Suhyun, Park, Seungeun, Lee, Hae-seok, E-mail: lhseok@korea.ac.kr, Kim, Donghwan, E-mail: donghwan@korea.ac.kr, Kang, Min Gu, Song, Hee-eun, & Kang, Yoonmook, E-mail: ddang@korea.ac.kr. Light-induced degradation and metastable-state recovery with reaction kinetics modeling in boron-doped Czochralski silicon solar cells. United States. doi:10.1063/1.4894289.
Kim, Soo Min, Chun, Seungju, Bae, Suhyun, Park, Seungeun, Lee, Hae-seok, E-mail: lhseok@korea.ac.kr, Kim, Donghwan, E-mail: donghwan@korea.ac.kr, Kang, Min Gu, Song, Hee-eun, and Kang, Yoonmook, E-mail: ddang@korea.ac.kr. Mon . "Light-induced degradation and metastable-state recovery with reaction kinetics modeling in boron-doped Czochralski silicon solar cells". United States. doi:10.1063/1.4894289.
@article{osti_22310987,
title = {Light-induced degradation and metastable-state recovery with reaction kinetics modeling in boron-doped Czochralski silicon solar cells},
author = {Kim, Soo Min and Chun, Seungju and Bae, Suhyun and Park, Seungeun and Lee, Hae-seok, E-mail: lhseok@korea.ac.kr and Kim, Donghwan, E-mail: donghwan@korea.ac.kr and Kang, Min Gu and Song, Hee-eun and Kang, Yoonmook, E-mail: ddang@korea.ac.kr},
abstractNote = {Solar cells fabricated from boron-doped p-type Czochralski silicon suffer from light-induced degradation that can lower the conversion efficiency by up to 10% relative. When solar cells are exposed to temperatures between 100 °C and 200 °C under illumination, regeneration, in which the minority carrier lifetime is gradually recovered, occurs after the initial light-induced degradation. We studied the light-induced degradation and regeneration process using carrier injection within a design chamber and observed open-circuit voltage trends at various sample temperatures. We proposed a cyclic reaction kinetics model to more precisely analyze the degradation and recovery phenomenon. Our model incorporated the reaction paths that were not counted in the original model between the three states (annealed, degradation, and regeneration). We calculated a rate constant for each reaction path based on the proposed model, extracted an activation energy for each reaction using these rate constants at various temperatures, and calculated activation energies of redegradation and the stabilization reaction.},
doi = {10.1063/1.4894289},
journal = {Applied Physics Letters},
number = 8,
volume = 105,
place = {United States},
year = {Mon Aug 25 00:00:00 EDT 2014},
month = {Mon Aug 25 00:00:00 EDT 2014}
}
  • A strong electric field has been shown to reverse the light-induced degradation of amorphous silicon solar cells while exposed to intense illumination at moderate temperatures. The rate of reversal increases with temperature, illumination intensity, and with the strength of the reverse bias field. The reversal process exhibits an activation energy on the order of 0.9 eV and can be increased by the trapping of either electrons or holes in the presence of a strong electric field. {copyright} {ital 1997 American Institute of Physics.}
  • We present results of computer simulations of the characteristics of amorphous silicon alloy p-i-n solar cells in both undegraded and degraded conditions for illumination through the n/sup +/ or p/sup +/ layers. Changes in device performance upon degradation correlate well with realistic changes in the minority carrier diffusion length of the intrinsic layer. The results of our model are in good agreement with experimental data and lead us to conclude that the observed degradation in the electronic properties of amorphous silicon alloys are only consistent with the observed increases in the localized state density if the photoinduced metastable defects havemore » larger capture cross sections than the localized states in as-deposited material. The analysis of recombination losses shows that upon degradation, primarily because of the decrease in the minority carrier diffusion length, cells illuminated through the n/sup +/ layer exhibit a loss of short-wavelength response whereas those illuminated through the p/sup +/ layer exhibit a loss of long-wavelength response.« less
  • The nature of light- and current-induced metastabilities under electrical bias in hydrogenated nanocrystalline silicon (nc-Si:H) solar cells has been found to be different from those in hydrogenated amorphous silicon (a-Si:H)-based solar cells. First, a forward-bias current injection in the dark does not cause any degradation in nc-Si:H cell performance. The phenomenon is explained by the percolation transport through crystalline paths, where the excess carrier recombination does not cause degradation. Second, a reverse bias does not reduce, but enhances the light-induced degradation in the nc-Si:H cell performance. The enhancement increases with the magnitude of the applied reverse bias. By measuring themore » quantum efficiency losses and color (blue, wavelength=390 nm and red, wavelength=670 nm) fill factors, we suggest that the reverse-bias-enhanced defect generation mostly takes place in the grain-boundary regions. Light-soaking experiments using light with different spectra show that a reverse bias under white light causes more enhancement in the degradation than under blue light (wavelength shorter than 650 nm). No degradation occurs under red light (wavelength longer than 665 nm) in either open-circuit or reverse-bias condition. A ''back-to-back'' diode model is proposed to explain these phenomena in terms of the heterogeneity of the material structure.« less
  • The effect of light illumination on the photovoltaic performances of hydrogenated amorphous silicon (a-Si:H) n/sup +/-p-p/sup +/ solar cells has been investigated. The degradation increases as the doping concentration of p-type a-Si:H increases, and it decreases with increasing the substrate (or annealing) temperature. These results indicate that the light-induced degradation increases with the microvoid density in the material. The increase of conversion efficiency has been observed for a-Si:H n/sup +/-p-p/sup +/ cells after light exposure, and this is due to the increase of doping efficiency for p-type a-Si:H during light illumination.