Revealing Micro-Scale Doping Variations in Thin-Films via Simultaneous Luminescence and Current Collection Measurements: Paper No. 116810E

Harvey Guthrey, Sean Jones, John Moseley, Brian Gorman, Mowafak Al-Jassim

Research output: Contribution to conferencePaper

Abstract

Doping thin films used for photovoltaic absorbers is both critical to maximize device voltage and challenging due to complex interactions between point defects in these materials. Such interactions can result in compensation of the intended dopant species, meaning that the active charge-carrier concentration is lower than the concentration incorporated dopants. Charge-carrier compensation is directly related to the open-circuit voltage (VOC) deficit, or magnitude of VOC relative to the theoretical limit. Understanding how the carrier concentration varies within thin-films is necessary to design material processing schedules to minimize this VOC deficit and produce more efficient devices. Unfortunately, measurements of the free carrier concentration are generally relevant at the device level and cannot resolve local differences. Resolving local doping differences in thin-films such as Cd(Se,Te), CZTS, and CIGSe requires techniques with micron or sub-micron spatial resolution due to the polycrystalline structure as well as intended and unintended composition variations in these materials. In this contribution, we show how simultaneous measurement of cathodoluminescence (CL) and electron-beam-induced current (EBIC) can be used to expose doping variations in Cd(Se,Te) thin-films. Simultaneous collection of these signals reveals unexpected differences in the electric field strength through the device thickness due to spatial variation in the carrier concentration.
Original languageAmerican English
Number of pages8
DOIs
StatePublished - 2021
EventPhysics, Simulation, and Photonic Engineering of Photovoltaic Devices X: SPIE -
Duration: 6 Mar 202112 Mar 2021

Conference

ConferencePhysics, Simulation, and Photonic Engineering of Photovoltaic Devices X: SPIE
Period6/03/2112/03/21

NREL Publication Number

  • NREL/CP-5K00-79151

Keywords

  • cathodoluminescence
  • doping
  • EBIC
  • photovoltaic
  • recombination

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