Alternating bias hot carrier solar cells

Patent metadata

Field	Value
Publication number	US-9722533-B2
Application number	US-201514724518-A
Country	US
Kind code	B2
Filing date	May 28, 2015
Priority date	Jul 9, 2010
Publication date	Aug 1, 2017
Grant date	Aug 1, 2017

Abstract

Designs of extremely high efficiency solar cells are described. A novel alternating bias scheme enhances the photovoltaic power extraction capability above the cell band-gap by enabling the extraction of hot carriers. When applied in conventional solar cells, this alternating bias scheme has the potential of more than doubling their yielded net efficiency. When applied in conjunction with solar cells incorporating quantum wells (QWs) or quantum dots (QDs) based solar cells, the described alternating bias scheme has the potential of extending such solar cell power extraction coverage, possibly across the entire solar spectrum, thus enabling unprecedented solar power extraction efficiency. Within such cells, a novel alternating bias scheme extends the cell energy conversion capability above the cell material band-gap while the quantum confinement structures are used to extend the cell energy conversion capability below the cell band-gap. Light confinement cavities are incorporated into the cell structure in order to allow the absorption of the cell internal photo emission, thus further enhancing the cell efficiency.

First claim

What is claimed is:

1. A method of operating a solar cell having a junction with a p-doped side and an n-doped side, and first and second contacts, the method comprising:
causing the photovoltage across the first and second contacts to periodically alternate between a minimum and a maximum voltage value of a same polarity during operation of the solar cell;
the period of alternation of the photovoltage between the minimum and maximum voltage values being shorter than the hot carrier cooling time for the solar cell to extract from the solar cell, during the alternation of the photovoltage, photo-excited carriers across a range of energy levels, including photo-excited hot carriers.

2. The method of claim 1 wherein the solar cell is a bulk material solar cell.

3. The method of claim 1 wherein the solar cell incorporates quantum confinement.

4. The method of claim 1 wherein:
the minimum photovoltage value is a photovoltage value at which the solar cell built-in potential is sufficiently high to cause acceleration of the photo-excited carriers within the solar cell toward first and second contacts of the solar cell with a transport velocity approaching or reaching its maximum value; and
the maximum photovoltage value being substantially equal to the maximum value of the electrochemical potential of the photo-excited carriers generated within the solar cell.

5. The method of claim 4 wherein a sub-period during which the solar cell photovoltage value approaches or reaches the minimum photovoltage value is selected to be short enough to maintain the average photovoltage achieved by the solar cell at or near the highest possible value and/or is selected to be long enough to sustain an average carrier transport velocity to transport substantially all of the photo-excited carriers within the solar cell to the first and second contacts of the solar cell within the hot carrier cooling time.

6. The method of claim 1 , further including at least one time interval, shorter than the period of alternation, during which the solar cell photovoltage reaches an opposite polarity value of a duration and period of repetition to sustain an average carrier transport velocity sufficient to transport substantially all of the photo-excited carriers within the solar cell to the first and second contacts within the hot carriers cooling time.

7. The method of claim 6 wherein a sub-period during which the solar cell photovoltage value approaches or reaches the minimum photovoltage value is selected to be long enough to sustain an average carrier transport velocity to transport substantially all of the photo-excited carriers within the solar cell to the first and second contacts of the solar cell within the hot carrier cooling time, the sub-period during which the solar cell photovoltage value approaches or reaches the minimum photovoltage value is selected to be short enough to keep the average photovoltage achieved by the solar cell at the highest possible value, and the period of periodically alternating between minimum and maximum photovoltage values and the ratio of the duration of the sub-period to the alternation period being selected responsive to the band-gap, carrier mobility and crystal lattice characteristics of the solar cell, allowing the extraction energy separation between the solar cell contacts to temporally sweep through a range of extraction energies that substantially matches the profile of the electrochemical potential of the photo-excited carriers within the solar cell, thus allowing a single junction solar cell to have the energy extraction efficiency benefits of a multi junction solar cell.

8. The method of claim 6 wherein a sub-period during which the solar cell photovoltage value approaches or reaches the minimum photovoltage value is selected to be long enough to sustain an average carrier transport velocity to transport substantially all of the photo-excited carriers within the solar cell to the first and second contacts of the solar cell within the hot carrier cooling time, the sub-period during which the solar cell photovoltage value approaches or reaches the minimum photovoltage value is selected to be short enough to keep the average photovoltage achieved by the solar cell at the highest possible value, and the period of periodically alternating between minimum and maximum photovoltage values and the ratio of the duration of the sub-period to the alternation period being selected responsive to the band-gap, carrier mobility and crystal lattice characteristics of the solar cell, thereby providing the extraction energy separation between the solar cell contacts to temporally sweep through a wide range of extraction energies at a rate that is comparable to or faster than the hot carrier cooling rate, allowing the photo-excited carriers that reach the solar cell contacts to be transferred to a solar cell load through a temporally discrete narrow extraction energy band at each contact and with instantaneous energy separation between the contacts that substantially equals the energy separation between the photo-excited carriers within the solar cell.

9. The method of claim 6 wherein the solar cell materials are selected from the group consisting of silicon (Si), gallium arsenide (GaAs), cadmium telluride (CdTe), copper indium diselenide (CIS), copper indium gallium diselenide (CIGS), and alloys of III-V materials.

10. The method of claim 9 wherein the alternation of the photovoltage values of the solar cell between the minimum and maximum photovoltage values extracts photo-excited carriers within the solar cell over a range of extraction energies that substantially matches the energy profile of the photo-excited carriers generated within the solar cell that spans from the band-gap energy of the solar cell materials to an energy that is substantially equal to the maximum value of the electrochemical potential of the hot carriers to be extracted from the solar cell.

11. The method of claim 9 wherein the solar cell comprises either quantum confinement structures or optical confinement structures or both.

12. The method of claim 11 wherein the alternation of the photovoltage values of the solar cell between the minimum and maximum photovoltage values extracts carriers within the solar cell that were photo-excited by solar photons having energy that extends over a range of energies extending from the band-gap energy of the solar cell materials to an energy that is substantially equal to the maximum value of the electrochemical potential of the hot carriers to be extracted from the solar cell.

13. The method of claim 11 wherein the alternation of the photovoltage values of the solar cell cause the extraction of carriers within the solar cell photo-excited by solar photons having energy that extend over a wide range of energies from substantially below the band-gap energy of the solar cell materials to an energy that is substantially equal to the maximum value of the electrochemical potential of the hot carriers to be extracted from the solar cell.

14. The method of claim 11 wherein the solar cell comprises quantum confinement structures having multiple quantum wells wherein the band-gap of the multiple quantum wells is graded to provide a range of different band-gap values for the quantum wells, with the range of different band-gap values being below the solar cell material band-gap value.

Assignees

• Ostendo Technologies Inc

Inventors

• El-Ghoroury Hussein S
• Mcneill Dale A
• Guncer Selim E

Classifications

• Y10S977/755

  Nanosheet or quantum barrier/well, i.e. layer structure having one dimension or thickness of 100 nm or less · CPC title

• Y02E10/547

  Monocrystalline silicon PV cells · CPC title

• Y02E10/544

  Solar cells from Group III-V materials · CPC title

• Y02E10/541

  CuInSe2 material PV cells · CPC title

• H02S40/34 Primary

  comprising specially adapted electrical connection means to be structurally associated with the PV module, e.g. junction boxes · CPC title