Publication detail

Near field photocurrent spectroscopy of crystalline GaAs solar cells

TOMÁNEK, P. GRMELA, L.

Original Title

Near field photocurrent spectroscopy of crystalline GaAs solar cells

Czech Title

Spektroskopie fotoproudu v blízkém poli krystalických GaAs solárních článků

English Title

Near field photocurrent spectroscopy of crystalline GaAs solar cells

Type

conference paper

Language

en

Original Abstract

Visible Scanning Near Field Optical Microscopy (SNOM) was used to study cleaved edges of GaAs solar cell devices. SNOM is a relatively new technique that combines the versatility of optical microscopy with the resolution of a scanning probe microscope. Light coupled into a tapered optical fiber is used for excitation. The fiber probe is scanned over the sample while being held ~10 nm above the surface. At this point, any number of high resolution (~100 nm) optical measurements can be made. In this work, we measured the NSOM-induced photocurrent in GaAs devices. Our goal was to obtain spatially resolved measurements of the photocurrent response across the various layers in crystalline GaAs solar cells, by studying the cleaved edges of the cells. For excitation energies well above the bandgap, carrier recombination at the cleaved surface had a strong influence on the photocurrent signal. Decreasing the excitation energy, which increased the optical penetration depth, allowed the effects of surface recombination to be separated from collection by the p-n junction. Using this approach, the SNOM measurements directly observed the effects of a buried minority carrier reflector/passivation layer. In conclusion, we have shown that surface recombination has a strong influence on cross sectional SNOM photocurrent measurements of GaAs diodes. Changing the excitation energy allows surface recombination to be separated from collection in the p-n junction. Additionally, we have directly observed the effects of minority carrier reflector layers which are included in solar cells to increase efficiency.

Czech abstract

Rastrovací optická mikroskopie v blízkém poli ve viditelné oblasti je relativně nová technika, která kombinuje všestrannost optického mikroskopu s rozlišením sondových mikroskopů. Světlo vevázané do hrotu optického vlákna excituje vzorek a je možné je použít ke spektroskopickým měřením. Zde je použito k meření SNOM indukovaného fotoproudu na GaAs součástkách. Cílem je dosáhnout měření odezvy fotoproudu různých vrstev krystalického GaAs slunečního článku s vysokým prostorovým rozlišením. K tomu se používá měření na hranách zlomu článků.

English abstract

Visible Scanning Near Field Optical Microscopy (SNOM) was used to study cleaved edges of GaAs solar cell devices. SNOM is a relatively new technique that combines the versatility of optical microscopy with the resolution of a scanning probe microscope. Light coupled into a tapered optical fiber is used for excitation. The fiber probe is scanned over the sample while being held ~10 nm above the surface. At this point, any number of high resolution (~100 nm) optical measurements can be made. In this work, we measured the NSOM-induced photocurrent in GaAs devices. Our goal was to obtain spatially resolved measurements of the photocurrent response across the various layers in crystalline GaAs solar cells, by studying the cleaved edges of the cells. For excitation energies well above the bandgap, carrier recombination at the cleaved surface had a strong influence on the photocurrent signal. Decreasing the excitation energy, which increased the optical penetration depth, allowed the effects of surface recombination to be separated from collection by the p-n junction. Using this approach, the SNOM measurements directly observed the effects of a buried minority carrier reflector/passivation layer. In conclusion, we have shown that surface recombination has a strong influence on cross sectional SNOM photocurrent measurements of GaAs diodes. Changing the excitation energy allows surface recombination to be separated from collection in the p-n junction. Additionally, we have directly observed the effects of minority carrier reflector layers which are included in solar cells to increase efficiency.

Keywords

solar cell, crystalline GaAs, local spectroscopy

RIV year

2004

Released

14.10.2004

Publisher

Vydavatelstvo STU Bratislava

Location

Trnava

ISBN

80-227-2117-4

Book

CO-MAT-TECH 2004, Proceeding of 12. International Scientific Conference

Pages from

1365

Pages to

1370

Pages count

6

BibTex


@inproceedings{BUT11605,
  author="Pavel {Tománek} and Lubomír {Grmela}",
  title="Near field photocurrent spectroscopy of crystalline GaAs solar cells",
  annote="Visible Scanning Near Field Optical Microscopy (SNOM) was used to study cleaved
edges of GaAs solar cell devices. SNOM is a relatively new technique that combines the
versatility of optical microscopy with the resolution of a scanning probe microscope. Light
coupled into a tapered optical fiber is used for excitation. The fiber probe is scanned over the
sample while being held ~10 nm above the surface. At this point, any number of high
resolution (~100 nm) optical measurements can be made. In this work, we measured the
NSOM-induced photocurrent in GaAs devices.
Our goal was to obtain spatially resolved measurements of the photocurrent response
across the various layers in crystalline GaAs solar cells, by studying the cleaved edges of the
cells. For excitation energies well above the bandgap, carrier recombination at the cleaved
surface had a strong influence on the photocurrent signal. Decreasing the excitation energy, which increased the optical penetration depth, allowed the effects of surface recombination to be separated from collection by the p-n junction. Using this approach, the SNOM
measurements directly observed the effects of a buried minority carrier reflector/passivation
layer.
In conclusion, we have shown that surface recombination has a strong influence on
cross sectional SNOM photocurrent measurements of GaAs diodes. Changing the excitation
energy allows surface recombination to be separated from collection in the p-n junction.
Additionally, we have directly observed the effects of minority carrier reflector layers which are included in solar cells to increase efficiency.
",
  address="Vydavatelstvo STU Bratislava",
  booktitle="CO-MAT-TECH 2004, Proceeding of 12. International Scientific Conference",
  chapter="11605",
  institution="Vydavatelstvo STU Bratislava",
  year="2004",
  month="october",
  pages="1365--1370",
  publisher="Vydavatelstvo STU Bratislava",
  type="conference paper"
}