Energy storage device with large charge separation
High density energy storage in semiconductor devices is provided. There are two main aspects of the present approach. The first aspect is to provide high density energy storage in semiconductor devices based on formation of a plasma in the semiconductor. The second aspect is to provide high density energy storage based on charge separation in a p-n junction.
1. An energy storage system comprising:
1) a plasma-based energy storage device comprising:
first and second conductive electrodes spaced apart;
a first volume of active material disposed between the electrodes; and
a first volume of barrier material disposed between the first volume of active material and the first electrode; and
2) a source configured to illuminate the plasma-based energy storage device with electromagnetic radiation having a photon energy greater than a band gap energy of the active material of the first active volume;
wherein upon application of a voltage across the electrodes one or both of an electron plasma or hole plasma is formed in the first volume of active material;
wherein the electron plasma and/or hole plasma independently have a density of charge carriers of greater than about 0.5 carrier per nm 3 when the first volume of active material is subject to a field of 0.7 V/nm; and
wherein the voltage applied across the electrodes to form the plasma in the first volume of active material produces an energy density of greater than about 1 Wh/L for the device.
2. The system of claim 1
wherein the barrier material in the first volume of barrier material has a first breakdown field strength, and
wherein the voltage applied across the electrodes to form the plasma in the first volume of active material produces an electric field in the first volume of barrier material less than the first breakdown field strength.
3. The system of claim 1 wherein upon application of the voltage across the electrodes, charge carriers are injected into the first volume of active material from the second electrode.
4. The system of claim 1 further comprising a second volume of barrier material disposed between the first volume of active material and the second electrode;
wherein the barrier material in the second barrier volume has a second breakdown field strength; and
wherein the voltage applied across the electrodes to form the plasma in the first volume of active material produces an electric field in the second barrier volume less than the second breakdown field strength.
5. The system of claim 1 wherein all linear dimensions of the first volume of active material are greater than about the bohr radius of an exciton in the active material of the first active volume.
6. The system of claim 1 wherein all linear dimensions of the first volume of active material are greater than about 100 nm.
7. The system of claim 1 wherein the first electrode is cylindrically shaped and the second electrode is disposed inside of the first electrode.
8. The system of claim 1 further comprising a second volume of active material disposed between the first volume of barrier material and the first electrode, wherein the distance between the first and second volumes of active material is greater than about 5 nm.
9. The system of claim 1 further comprising a second volume of active material disposed between the first volume of barrier material and the first electrode, wherein upon application of a voltage across the electrodes charge carriers are injected into the first volume of active material from the second electrode and into the second volume of active material from the first electrode.
10. The system of claim 1 further comprising a second volume of active material disposed between the first volume of barrier material and the first electrode, wherein the first volume of active material has a first Fermi level and the second volume of active material has a second Fermi level different from the first Fermi level.