Thermal emissivity of silicon heterojunction solar cells

D. Alonso-Álvarez, A. Augusto, P. Pearce, L. Ferre Llin, A. Mellor, S. Bowden, D. J. Paul, N. Ekins-Daukes

Research output: Contribution to journalArticlepeer-review

9 Scopus citations


The aim of this work is to evaluate whether silicon heterojunction solar cells, lacking highly emissive, heavily doped silicon layers, could be better candidates for hybrid photovoltaic thermal collectors than standard aluminium-diffused back contact solar cells. To this end, the near and mid infrared emissivity of full silicon heterojunction solar cells, as well as of its constituent materials – crystalline silicon wafer, indium tin oxide, n-, i- and p-type amorphous silicon – have been assessed by means of ellipsometry and FTIR. The experimental results show that the thermal emissivity of these cells is actually as high as in the more traditional structures, ~80% at 8 μm. Detailed optical modelling combining raytracing and transfer matrix formalism shows that the emissivity in these cells originates in the transparent conductive oxide layers themselves, where the doping is not high enough to result in a reflection that exceeds the increased free carrier absorption. Further modelling suggests that it is possible to obtain lower emissivity solar cells, but that a careful optimization of the transparent conductive layer needs to be done to avoid hindering the photovoltaic performance.

Original languageEnglish (US)
Article number110051
JournalSolar Energy Materials and Solar Cells
StatePublished - Oct 2019


  • Emissivity
  • Heterojunction
  • Modelling
  • Silicon
  • Solar cells

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Renewable Energy, Sustainability and the Environment
  • Surfaces, Coatings and Films


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