intermediate band solar cells
Advanced Inorganic & novel Hybrid Materials
The research in intermediate band Solar cell (IBSC) aims to exceeding the Shockley–Queisser limit  on the efficiency of a cell by introducing intermediate band (IB) energy level between the valence and conduction bands of the semiconductor-like material . This increases the induced photocurrent and thereby efficiency
Prof. A.Luque and A.Martì first derived a theoretical limit for an IB device with one midgap energy level using detailed balance  They assumed no carriers were collected at the IB and that the device was under full concentration  They found the maximum efficiency to be 63.2%, for a bandgap of 1.95eV with the IB 0.71eV from either the valence or conduction band. Under one sun illumination the limiting efficiency is 47%.
Green and Brown expanded upon these results by deriving the theoretical efficiency limit for a device with infinite IBs. By introducing more IB’s, even more of the incident spectrum can be utilized. After performing the detailed balance, they found the maximum efficiency to be 77.2%.
IBs have theoretical potential to become high efficiency devices, but they are hard to make.
Many approaches have been proposed for engineering this IB. We list next some of the strategies being followed to identify these materials and implement solar cells with them:
- Quantum dots ,
- Insertion of impurities at high densities ,
- Highly mismatched alloys ,
- First principle calculations ,
- Dye sensitized + TT annihilation 
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 A. Marti and A. Luque, "Electrochemical Potentials (Quasi-Fermi Levels) and the Operation of Hot-Carrier, Impact-Ionization, and Intermediate-Band Solar Cells," Photovoltaics, IEEE Journal of, vol. 3, pp. 1298-1304, 2013.
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Prof. A. Martí and prof. A. Luque have been within the pioneers in proposing new concepts for solar cells could provide large photogenerated currents while maintaining a high output voltage. By this on-line course prof. Martì helps to understand the fundamentals of the intermediate band solar cell,