High Efficiency and Junction-less Solar Cell with Metal Insulator Semiconductor (MIS)

Background: Researchers in Prof. Krishna Saraswat’s laboratory have developed a low-cost efficient solar cell using specific classes of oxides in an interfacial layer of metal insulator semiconductor contacts. The technology identifies two classes of materials that can be used to selectively block either electrons or holes and improve open circuit voltage with low contact resistance. This approach enables two types of solar cells: 1) conventional p-n junction cells made without highly doped p and n materials; and 2) junction-less solar cells with optimized band line up with common semiconductors. The contact design could also be used for photodetectors. Technology Description: The present invention is related to (i) metal insulator semiconductor (MIS) contacts applied to conventional p-n junction solar cell eliminating highly doped p and n selective emitter and base contacts and (ii) the use of interfacial metal oxides having optimized band lineup with common semiconductors which makes a novel junction-less solar cell possible. In junction-less solar cell instead of forming a dopant diffused p-n junction for facilitating selectivity between electrons and holes interfacial metal oxides have been used. Intrinsic semiconductor acts as the absorber material for solar energy. While P and N diffusions using dopants are most commonly used for realizing selective contacts in solar cells they lead to degradation of quantum efficiency for high energy photons and also degradation of cell characteristics due to high thermal budget associated with their formation. Even for a p-n junction solar cell achieving high selectivity between electrons and holes at a specific contact is still a challenge. The most commonly used silicon cell design employs selective emitter where regions under the contact are highly doped while the rest of the surface is passivated with SiO2. Highly doped region provides a selective contact for one kind of carrier however it also acts as a recombination region for minority carrier. Hence the electron and hole pairs generated in the highly doped region often recombine before they are extracted. Fermi level pinning of metal at the interface creates a large Schottky barrier in metal-semiconductor contacts thereby increasing the contact resistivity. The purpose of this invention is related to overcoming these challenges by replacing highly doped n and p contact region with interfacial oxides and utilizing these oxides design a junction-less solar cell where no diffused p-n junction will be required. Applications: 1) Communications 2) Solar cells


1) Simple low cost fabrication 2) Efficient 3) Improved lifetime

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