Effect of light intensity on current collection in thin-film solar cells

Author

McMahon, T.J. ; von Roedern, B.

Author_Institution

Nat. Renewable Energy Lab., Golden, CO, USA

fYear

1997

fDate

29 Sep-3 Oct 1997

Firstpage

375

Lastpage

378

Abstract

We have measured the current-voltage curves of thin-film solar cells using focused laser spots (30-500 μm) using DC and modulated (AC) photocurrent techniques. The AC short-circuit current response (I _SC) and the AC fill factors (FF) decrease for small spot sizes corresponding to several 100 sun light intensities. Laser line scans across the devices produced significant but reproducible spatial fluctuations in AC I_SC. These spatial variations depend on spot size and are reduced by scanning with lower light intensity. The reduction of AC FF and AC I_SC was largest in a-Si:H, intermediate in CdTe and CuInSe₂ (CIS), barely noticeable in some Cu(Ga,In)Se₂ (CIGS) cells and absent in a silicon cells. The observations on CIGS and some CIS cells can be explained by internal series resistance, but field dependent collection and recombination effects must be invoked to explain results on most thin-film solar cell materials. Such field modification is not accounted for in standard exponential diode equation models

Keywords

II-VI semiconductors; amorphous semiconductors; cadmium compounds; copper compounds; electric current measurement; elemental semiconductors; hydrogen; indium compounds; measurement by laser beam; photoconductivity; semiconductor thin films; short-circuit currents; silicon; solar cells; ternary semiconductors; voltage measurement; 100 sun light intensities; 30 to 500 mum; AC fill factors; AC short-circuit current response; CdTe; CdTe solar cells; Cu(Ga,In)Se₂ solar cells; Cu(GaIn)Se₂; CuInSe₂; CuInSe₂ solar cells; DC photocurrent; Si; Si solar cells; Si:H; a-Si:H solar cells; current collection; current-voltage curves measurement; exponential diode equation models; field dependent collection; field modification; focused laser spots; internal series resistance; laser line scans; light intensity effect; modulated photocurrent; recombination effects; spot size; thin-film solar cells; Computational Intelligence Society; Current measurement; Diodes; Equations; Fluctuations; Photoconductivity; Photovoltaic cells; Silicon; Sun; Transistors;

fLanguage

English

Publisher

ieee

Conference_Titel

Photovoltaic Specialists Conference, 1997., Conference Record of the Twenty-Sixth IEEE

Conference_Location

Anaheim, CA

ISSN

0160-8371

Print_ISBN

0-7803-3767-0

Type

conf

DOI

10.1109/PVSC.1997.654106

Filename

654106