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July, 25 2014

Introduction



IBPOWER: Intermediate Band Materials and Solar Cells for Photovoltaics with High Efficiency and Reduced Cost, ref: 211640, is a Research Collaborative Project funded by the European Commission under the call FP7- ENERGY-2007-1-RTD. The Project started in February 1st , 2008 and has a duration of 4 years.

IBPOWER is devoted to the development of the intermediate band solar cell (IBSC) concept1. The IBSC is implemented on the basis of intermediate band materials. Typically these materials are characterised by the existence of the so-called "intermediate band" (IB) within a semiconductor bandgap. This IB splits the bandgap into two two-subbandgpas, EL and EH (Fig. 1) and allows the absorption of below-bandgap energy photons. Thanks to the IB, the absorption of two below bandgap energy photons (photons "1" and "2") creates one electron-hole pair that adds to the ones conventionally generated by the absorption of photons with energy higher than the bandgap EG (photon "3"). This increases the solar cell photocurrent. In order to be able to absorb the two below bandgap energy photons, the IB must be partially filled with electrons so it can provide both empty states to accomodate electrons from the valence band (VB) as to provide electrons to be pumped to the conduction band (CB) 

However, increasing the cell photocurrent is not enough (it could be easily done by choosing a low bandgp semiconductor for manufacturing the cell) if the potential for achieving a high output voltage is not preserved. To this end, according to the fundamental IBSC theory, the IB material must be sandwitched between two conventional semiconductors2 (emitters) to isolate the IB from the electrical contacts. The output voltage is determined then by the electron and hole quasi-Fermi level split (eV=EFE-EFH) and is still limited by the total bandgap EG.

The project pursues the implementation of the IBSC through different research lines, as for example:

  • The use of quantum dots3,4,5
  • The creation of low cost thin-film intermediate band materials6.

The Consortium is formed by the following participants:

  • The Universidad Politécnica de Madrid, through its Instituto de Energía Solar (Coordinator). (This web)
  • The University of Glasgow (link)
  • The Hahn Meitner Institute (link)
  • Riber S.A. (link)
  • The University of Nottingham (link)

Fig. 1. Description of the structure and operation of an intermediate band solar cell.


[1] A. Luque and A. Martí, "Increasing the Efficiency of Ideal Solar Cells by Photon Induced Transitions at Intermediate Levels," Physical Review Letters, vol. 78, p. 5014, 1997.

[2] A. Luque and A. Martí, "A metallic intermediate band high efficiency solar cell," Progress in Photovoltaics: Res. Appl., vol. 9, pp. 73-86, 2001.

[3]  A. Martí, L. Cuadra, and A. Luque, "Quantum dot intermediate band solar cell," in Proc. of the 28th IEEE Photovoltaics Specialists Conference, IEEE, Ed. New York, 2000, pp. 904-943.

[4] A. Martí, L. Cuadra, and A. Luque, "Intermediate Band Solar Cells," in NEXT GENERATION PHOTOVOLTAICS: High Efficiency through Full Spectrum Utilization, A. Martí and A. Luque, Eds. Bristol: Institute of Physics Publishing, 2003, pp. 140-162.

[5] A. Martí, C. R. Stanley, and A. Luque, "Intermediate Band Solar Cells (IBSC) using nanotechnolgy," in Nanostructured Materials for Solar Energy Conversion T. Soga, Ed.: Elsevier, 2006.

[6] A. Marti, D. F. Marron, and A. Luque, "Evaluation of the efficiency potential of intermediate band solar cells based on thin-film chalcopyrite materials," Journal of Applied Physics, vol. 103, pp. 073706-6, 2008.