The detailed balance method is used to study the thermodynamic efficiency of an intermediate band photovoltaic cell with low threshold Auger generation. Hot electrons generated by high-energy photons pump electrons from the intermediate band to the conduction band. The intermediate band is filled up after absorption of low-energy photons. A thermodynamic efficiency of about 70% is obtained, which is higher than the maximal efficiency of 63.2% for an intermediate band solar cell without Auger generation. The optimum band gap is shifted towards the silicon band gap. This result gives silicon its place in the new generation of solar cell materials using generation mechanism absent in single-band-gap solar cells.

Si modifications implemented at the nanoscale lead to optoelectronic and photovoltaic effects that can widen applications of conventional Si devices. The investigation exploits charge carrier and photon flux transformations at a so-called carrier collection limit. Comparison of the collection efficiencies of the same sample with and without a buried nanosystem allows a better understanding of the optical (absorbance) and electronic (carrier collection) behaviors. Experimental evidence for enhanced absorbance of a strained nanoscale Si-layered system has been found.

The experimental collection efficiency of a nanoscale Si-layered system formed around a buried amorphization is investigated. A self-consistent calculation that takes into account the number of photons removed in the front deactivated zone and those transmitted to deeper layers leads to the result that more than one electron per absorbed short-wavelength photon is collected in the active zone lying below a carrier collection limit. This result suggests that it could be possible to make an efficient third generation Si solar cell based on such a design on the condition that photocarriers generated in the surface zone be collected.

No abstract

No abstract