Effect of Light Intensity on Current Collection in Thin-Film Solar Cells

Research output: Contribution to conferencePaper


We have measured the current-voltage curves of thin-film solar cells using focused laser spots (30 - 500 mm) 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 reproduciblespatial 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 CuInSe 2 (CIS), barely noticeable in some Cu(Ga,In)Se 2 (CIGS) cells and absent in a silicon cells. The observations on CIGS and some CIS cells can be explained by internal seriesresistance, 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.
Original languageAmerican English
Number of pages4
StatePublished - 1997
EventTwenty Sixth IEEE Photovoltaic Specialists Conference - Anaheim, California
Duration: 29 Sep 19973 Oct 1997


ConferenceTwenty Sixth IEEE Photovoltaic Specialists Conference
CityAnaheim, California

Bibliographical note

For preprint version, including full text online document, see NREL/CP-520-22921

NREL Publication Number

  • NREL/CP-520-24961


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