Document Type

Conference Proceeding

Publication Date

3-2011

Publisher

National Renewable Energy Laboratory

First page number:

1

Last page number:

9

Abstract

Transient or hysteresis effects in polycrystalline thin film CdS/CdTe cells are a function of pre-measurement voltage bias and whether Cu is introduced as an intentional dopant during back contact fabrication. When Cu is added, the current-density (J) vs. voltage (V) measurements performed in a reverse-to-forward voltage direction will yield higher open-circuit voltage (Voc), up to 10 mV, and smaller short-circuit current density (Jsc), by up to 2 mA/cm2, relative to scanning voltage in a forward-to-reverse direction. The variation at the maximum power point, Pmax, is however small. The resulting variation in FF can be as large as 3%. When Cu is not added, hysteresis in both Voc and Jsc is negligible however Pmax hysteresis is considerably greater. This behavior corroborates observed changes in depletion width, Wd, derived from capacitance (C) vs. voltage (V) scans. Measured values of Wd are always smaller in reverse-to-forward voltage scans, and conversely, larger in the forward-to-reverse voltage direction. Transient ion drift (TID) measurements performed on Cu-containing cells do not show ionic behavior suggesting that capacitance transients are more likely due to electronic capture-emission processes. J-V curve simulation using Pspice shows that increased transient capacitance during light-soak stress at 100 ºC correlates with increased space-charge recombination. Voltage-dependent collection however was not observed to increase with stress in these cells.

Keywords

Cadmium; CdTe solar cell; DLTS; Degradation; Photovoltaic cells – Deterioration; Photovoltaic cells – Reliability; Reliability (Engineering); Solar cells – Deterioration; Solar cells – Reliability; Solar energy; Telluride; Thin films; Transient capacitance; Transient ion drift; Voltage-dependent collection

Disciplines

Oil, Gas, and Energy | Power and Energy

Language

English

Comments

Presented at the Reliability of Photovoltaic Cells, Modules, Components, and Systems III: SPIE Conference, August 3-5, 2010, San Diego, California.


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