Effect of Hysteresis on Measurements of Thin-Film Cell Performance

Research output: Contribution to conferencePaper

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, andsmaller 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 observedchanges 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 toelectronic capture-emission processes. J-V curve simulation using Pspice shows that increased transient capacitance during light-soak stress at 100 degrees C correlates with increased space-charge recombination. Voltage-dependent collection however was not observed to increase with stress in these cells.
Original languageAmerican English
Number of pages12
StatePublished - 2011
EventSPIE Conference - San Diego, California
Duration: 3 Aug 20105 Aug 2010

Conference

ConferenceSPIE Conference
CitySan Diego, California
Period3/08/105/08/10

NREL Publication Number

  • NREL/CP-5200-48996

Keywords

  • CdTe solar cells
  • degradation
  • DLTS
  • reliability
  • transient capacitance
  • transient ion drift (TID)
  • voltage-dependent collection

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