Energy Conversion Efficiency Mechanisms In Quantum Dot Intermediate Band Nanostructure Solar Cells

1. CONCLUSION

1.1. This article considered a study on principles of the MEG and IB QDs solar cells. Inserting QDs as very efficient particles to enhance photocurrents and managing the efficiency of the 3th generation of SCs have been investigated. For example, three types of configurations for QD solar cells are described here which can produce enhanced photocurrent, and the thermodynamic efficiencies.

2. Introduction to the subject

2.1. We have reviewed the application of quantization effects in nanocrystal particles to produce third-generation Quantum Dot (QD) Solar Cells (SC) that leads to very low cost solar electricity. We discuss two roads based on semiconductor QDs and QDs arrays that will lead to ultrahigh efficiencies through enhanced photocurrent.

3. INTERMEDIATE-BAND SOLAR CELLS

3.1. To capture and use photons which are less than the bandgap energy, IB solar cells are based on intermediate band materials

3.1.1. These materials are characterized by the existence of an intermediate band located between the conventional semiconductor conduction band (CB) and valence band (VB) Due to the IB, photons with energy below the bandgap can contribute to the cell photocurrent by exciting electrons from the VB to the IB and from the IB to the CB.

4. MULTIPLE EXCITON GENERATION SOLAR CELLS

4.1. The Shockley and Queisser efficiency is accessible in semiconductors with bandgaps ranging from about 1.25 to 1.45 eV, while the solar spectrum contains photons with energies ranging from about 0.5 to 3.5 eV. Photon energy below the semiconductor bandgap does not absorb, while for energies above the bandgap charge carriers (electrons and holes) with a total excess kinetic energy equal to the difference between the photon energy and the bandgap will produce. Such carriers are named as „hot electrons and hot holes. There are two fundamental pathways to prevent the thermalization loss produced from the absorption of high-energy photons above the bandgap in a single-bandgap system. One way produces an enhanced photovoltage and the other way produces an enhanced photocurrent. Furthermore, in full solar concentration (46,050 suns), both approaches converge at 86% conversion efficiency