• Isoaho, Riku
• Aho, Timo Antero
• Aho, Arto Johannes
• Polojärvi, Ville Valtteri
• Raappana, Marianna Jenni Sofia
• Guina, Mircea
• Tukiainen, Antti

Abstract

Multijunction III-V solar cells have the highest conversion efficiencies among all photovoltaic devices with current world record of 46 %, measured under concentrated light [1]. Furthermore, III-V semiconductor solar cells are found to be the best choice for generating electricity for satellites, because of high power-to-mass ratio and good radiation hardness. Although so far, the record conversion efficiency has increased almost one percentage point per year, new materials and concepts are needed to overcome the 50 % conversion efficiency barrier. <br/><br/>To this end, one of the most promising III-V photovoltaic material families is dilute nitrides. Introducing nitrogen to GaInAs shrinks the band gap by influencing the conduction band, and forming a localized band inside the material [2]. Nitrogen also compensates the compressive strain caused by In, when material is grown on GaAs or Ge substrates, preventing the formation of harmful dislocations. Capability to achieve a band gap between 1.4-0.8 eV and still maintain lattice matching [3], makes GaInNAs a good candidate as a part of multijunction solar cell with conversion efficiency exceeding 50 %.<br/><br/>In this presentation we discuss the use of optimized [4] bulk GaInNAs hetero-structures in multijunction solar cell (Figure 1.). Moreover, we have used GaInNAs and GaNAs for strain compensation and mediation, to absorb photons, and to boost the thermal escape of charge carriers in InAs quantum dot solar cell [5]. The properties of the dilute nitride based solar cells developed will be discussed.<br/><br/> <br/><br/>Figure 1: A photograph of multijunction solar cell for concentrator applications, designed, fabricated and processed by the authors at Optoelectronics Research Centre, Tampere University of Technology.<br/><br/>References<br/>[1] M. A. Green, K. Emery, Y. Hishikawa, W. Warta and E. D. Dunlop, Prog. Photovoltaics Res. Appl. 23, 805 (2015).<br/>[2] M. Henini (Ed.), Dilute Nitride Semiconductors(Elsevier, Amsterdam, 2005).<br/>[3] J. S. Harris, R. Kudrawiec, H. Yuen, S. Bank, H. Bae, M. Wistey, D. Jackrel, E. Pickett, T. Sarmiento and L. Goddard, Phys. Status Solidi B 244,2707 (2007).<br/>[4] A. Aho, V. Polojärvi, V.-M. Korpijärvi, J. Salmi, A. Tukiainen, P. Laukkanen and M. Guina, Solar Energy Mater. Solar Cells 124, 150 (2014).<br/>[5] V. Polojärvi, E.-M. Pavelescu, A. Schramm, A. Tukiainen, A. Aho, J. Puustinen and M. Guina, Scr. Mater. 108, 122 (2015).<br/>

Topics

• impedance spectroscopy
• Nitrogen
• nitride
• hardness
• dislocation
• forming
• quantum dot
• III-V semiconductor