Measurement of minority-carrier diffusion lengths using wedge-shaped semiconductor photoelectrodes

Ragip A. Pala, Andrew J. Leenheer, Michael Lichterman, Harry A. Atwater, Nathan S Lewis

Research output: Contribution to journalArticle

32 Citations (Scopus)

Abstract

Measurement of the photocurrent as a function of the thickness of a light absorber has been shown herein both theoretically and experimentally to provide a method for determination of the minority-carrier diffusion length of a sample. To perform the measurement, an illuminated spot of photons with an energy well above the band gap of the material was scanned along the thickness gradient of a wedge-shaped, rear-illuminated semiconducting light absorber. Photogenerated majority carriers were collected through a back-side transparent ohmic contact, and a front-side liquid or Schottky junction collected the photogenerated minority carriers. Calculations showed that the diffusion length could be evaluated from the exponential variation in photocurrent as a function of the thickness of the sample. Good agreement was observed between experiment and theory for a solid-state silicon Schottky junction measured using this method. As an example for the application of the technique to semiconductor/liquid-junction photoelectrodes, the minority-carrier diffusion length was determined for graded thickness, sputtered tungsten trioxide and polished bismuth vanadate films under back-illumination in contact with an aqueous electrolyte. This wedge technique does not require knowledge of the spectral absorption coefficient, doping, or surface recombination velocity of the sample.

Original languageEnglish
Pages (from-to)3424-3430
Number of pages7
JournalEnergy and Environmental Science
Volume7
Issue number10
DOIs
Publication statusPublished - Oct 1 2014

Fingerprint

Semiconductor materials
Photocurrents
liquid
bismuth
Ohmic contacts
absorption coefficient
Liquids
Silicon
tungsten
Bismuth
electrolyte
Electrolytes
recombination
silicon
Tungsten
Energy gap
Photons
Lighting
Doping (additives)
energy

ASJC Scopus subject areas

  • Renewable Energy, Sustainability and the Environment
  • Environmental Chemistry
  • Pollution
  • Nuclear Energy and Engineering

Cite this

Measurement of minority-carrier diffusion lengths using wedge-shaped semiconductor photoelectrodes. / Pala, Ragip A.; Leenheer, Andrew J.; Lichterman, Michael; Atwater, Harry A.; Lewis, Nathan S.

In: Energy and Environmental Science, Vol. 7, No. 10, 01.10.2014, p. 3424-3430.

Research output: Contribution to journalArticle

Pala, Ragip A. ; Leenheer, Andrew J. ; Lichterman, Michael ; Atwater, Harry A. ; Lewis, Nathan S. / Measurement of minority-carrier diffusion lengths using wedge-shaped semiconductor photoelectrodes. In: Energy and Environmental Science. 2014 ; Vol. 7, No. 10. pp. 3424-3430.
@article{44c56477484e43568a34a08805bd0157,
title = "Measurement of minority-carrier diffusion lengths using wedge-shaped semiconductor photoelectrodes",
abstract = "Measurement of the photocurrent as a function of the thickness of a light absorber has been shown herein both theoretically and experimentally to provide a method for determination of the minority-carrier diffusion length of a sample. To perform the measurement, an illuminated spot of photons with an energy well above the band gap of the material was scanned along the thickness gradient of a wedge-shaped, rear-illuminated semiconducting light absorber. Photogenerated majority carriers were collected through a back-side transparent ohmic contact, and a front-side liquid or Schottky junction collected the photogenerated minority carriers. Calculations showed that the diffusion length could be evaluated from the exponential variation in photocurrent as a function of the thickness of the sample. Good agreement was observed between experiment and theory for a solid-state silicon Schottky junction measured using this method. As an example for the application of the technique to semiconductor/liquid-junction photoelectrodes, the minority-carrier diffusion length was determined for graded thickness, sputtered tungsten trioxide and polished bismuth vanadate films under back-illumination in contact with an aqueous electrolyte. This wedge technique does not require knowledge of the spectral absorption coefficient, doping, or surface recombination velocity of the sample.",
author = "Pala, {Ragip A.} and Leenheer, {Andrew J.} and Michael Lichterman and Atwater, {Harry A.} and Lewis, {Nathan S}",
year = "2014",
month = "10",
day = "1",
doi = "10.1039/c4ee01580k",
language = "English",
volume = "7",
pages = "3424--3430",
journal = "Energy and Environmental Science",
issn = "1754-5692",
publisher = "Royal Society of Chemistry",
number = "10",

}

TY - JOUR

T1 - Measurement of minority-carrier diffusion lengths using wedge-shaped semiconductor photoelectrodes

AU - Pala, Ragip A.

AU - Leenheer, Andrew J.

AU - Lichterman, Michael

AU - Atwater, Harry A.

AU - Lewis, Nathan S

PY - 2014/10/1

Y1 - 2014/10/1

N2 - Measurement of the photocurrent as a function of the thickness of a light absorber has been shown herein both theoretically and experimentally to provide a method for determination of the minority-carrier diffusion length of a sample. To perform the measurement, an illuminated spot of photons with an energy well above the band gap of the material was scanned along the thickness gradient of a wedge-shaped, rear-illuminated semiconducting light absorber. Photogenerated majority carriers were collected through a back-side transparent ohmic contact, and a front-side liquid or Schottky junction collected the photogenerated minority carriers. Calculations showed that the diffusion length could be evaluated from the exponential variation in photocurrent as a function of the thickness of the sample. Good agreement was observed between experiment and theory for a solid-state silicon Schottky junction measured using this method. As an example for the application of the technique to semiconductor/liquid-junction photoelectrodes, the minority-carrier diffusion length was determined for graded thickness, sputtered tungsten trioxide and polished bismuth vanadate films under back-illumination in contact with an aqueous electrolyte. This wedge technique does not require knowledge of the spectral absorption coefficient, doping, or surface recombination velocity of the sample.

AB - Measurement of the photocurrent as a function of the thickness of a light absorber has been shown herein both theoretically and experimentally to provide a method for determination of the minority-carrier diffusion length of a sample. To perform the measurement, an illuminated spot of photons with an energy well above the band gap of the material was scanned along the thickness gradient of a wedge-shaped, rear-illuminated semiconducting light absorber. Photogenerated majority carriers were collected through a back-side transparent ohmic contact, and a front-side liquid or Schottky junction collected the photogenerated minority carriers. Calculations showed that the diffusion length could be evaluated from the exponential variation in photocurrent as a function of the thickness of the sample. Good agreement was observed between experiment and theory for a solid-state silicon Schottky junction measured using this method. As an example for the application of the technique to semiconductor/liquid-junction photoelectrodes, the minority-carrier diffusion length was determined for graded thickness, sputtered tungsten trioxide and polished bismuth vanadate films under back-illumination in contact with an aqueous electrolyte. This wedge technique does not require knowledge of the spectral absorption coefficient, doping, or surface recombination velocity of the sample.

UR - http://www.scopus.com/inward/record.url?scp=84907970892&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84907970892&partnerID=8YFLogxK

U2 - 10.1039/c4ee01580k

DO - 10.1039/c4ee01580k

M3 - Article

AN - SCOPUS:84907970892

VL - 7

SP - 3424

EP - 3430

JO - Energy and Environmental Science

JF - Energy and Environmental Science

SN - 1754-5692

IS - 10

ER -