Effects of high photon gas density and radiative efficiency on upper bounds of energy conversion efficiency in single-crystal solar cells

Sean J. Babcock, Nicholas P. Irvin, Eric Y. Chen, Christiana B. Honsberg, Richard R. King

Research output: Chapter in Book/Report/Conference proceedingConference contribution

3 Scopus citations


The strong dependence that open-circuit voltage has on photon recycling may be the key to push photovoltaic cells closer to their Shockley-Queisser efficiency limit. Photon recycling can be improved by the use of a highly reflective mirror at the back-surface. Therefore, it is important to maximize the mirror area while maintaining sufficient conductivity for carrier collection. In this work, efficiency limit calculations are used to model rear surface reflector effects on cell performance while varying reflectance and surface area of the rear reflector. The lateral and contact resistance due to the back-surface field layer and point contact geometry are then calculated. Finally, point contact size and coverage are optimized to maximize benefits from rear reflectance, while providing enough contact coverage to minimize resistive power loss. As a result, an optimized one-sun efficiency of 32.7% is calculated for GaAs solar cells with a practical, rather than idealized, back surface reflector structure. The optimum taking into account the competing effects of enhanced photon recycling vs. back contact series resistance occurs at less than 1% point contact coverage for 4 μm diameter contacts which can be achieved using standard photolithography and physical vapor deposition techniques.

Original languageEnglish (US)
Title of host publication2019 IEEE 46th Photovoltaic Specialists Conference, PVSC 2019
PublisherInstitute of Electrical and Electronics Engineers Inc.
Number of pages5
ISBN (Electronic)9781728104942
StatePublished - Jun 2019
Event46th IEEE Photovoltaic Specialists Conference, PVSC 2019 - Chicago, United States
Duration: Jun 16 2019Jun 21 2019

Publication series

NameConference Record of the IEEE Photovoltaic Specialists Conference
ISSN (Print)0160-8371


Conference46th IEEE Photovoltaic Specialists Conference, PVSC 2019
Country/TerritoryUnited States


  • GaAs
  • Shockley-Queisser limit
  • external radiative efficiency
  • photon recycling
  • solar cells

ASJC Scopus subject areas

  • Control and Systems Engineering
  • Industrial and Manufacturing Engineering
  • Electrical and Electronic Engineering


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