HIGH SPEED LASER CRYSTALLIZATION OF PARTICLES OF PHOTOVOLTAIC SOLAR CELLS

• US 20120021559A1
• Filed: 05/23/2011
• Published: 01/26/2012
• Est. Priority Date: 05/24/2010
• Status: Active Grant

• Current Assignee: Purdue Research Foundation (Purdue University)
• Original Assignee: Purdue Research Foundation (Purdue University)
• Inventors: Cheng, Gary J., Yang, Yingling, Zhang, Martin Yi
• Granted Patent: US 8,349,713 B2
• Time in Patent Office: Days
• US Class Current: 438/95
• CPC Class Codes: B23K 26/352 for surface treatment
• CPC Class Codes: H01L 31/0322 comprising only AIBIIICVI chalcopyrite compounds, e.g. Cu In Se2, Cu Ga Se2, Cu In Ga Se2
• CPC Class Codes: H01L 31/03923 including AIBIIICVI compound materials, e.g. CIS, CIGS
• CPC Class Codes: H01L 31/03925 including AIIBVI compound materials, e.g. CdTe, CdS
• CPC Class Codes: H01L 31/1836 comprising a growth substrate not being an AIIBVI compound
• CPC Class Codes: H01L 31/1852 comprising a growth substrate not being an AIIIBV compound
• CPC Class Codes: H01L 31/1872 Recrystallisation
• CPC Class Codes: Y02E 10/541 CuInSe2 material PV cells
• CPC Class Codes: Y02E 10/544 Solar cells from Group III-V materials
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product

Abstract

A system and method for enhancing the conversion efficiency of thin film photovoltaics. The thin film structure includes a photovoltaic absorbent layer covered by a confinement layer. A laser beam passes through the confinement layer and hits the photovoltaic absorbent layer. The laser can be pulsed to create localized rapid heating and cooling of the photovoltaic absorbent layer. The confinement layer confines the laser induced plasma plume creating a localized high-pressure condition for the photovoltaic absorbent layer. The laser beam can be scanned across specific regions of the thin film structure. The laser beam can be pulsed as a series of short pulses. The photovoltaic absorbent layer can be made of various materials including copper indium diselenide, gallium arsenide, and cadmium telluride. The photovoltaic absorbent layer can be sandwiched between a substrate and the confinement layer, and a molybdenum layer can be between the substrate and the photovoltaic absorbent layer.

Claims

1. A method for enhancing the conversion efficiency of thin film photovoltaics, the method comprising:

obtaining a thin film structure including a photovoltaic absorbent layer;

transmitting a laser beam along an optical path to hit the photovoltaic absorbent layer of the thin film structure;

pulsing the laser beam to create a localized rapid heating and cooling of the photovoltaic absorbent layer; and

transparently confining the photovoltaic absorbent layer to confine a laser induced plasma plume and create a localized high-pressure condition for the photovoltaic absorbent layer.

2. The method of claim 1, wherein the photovoltaic absorbent layer is selected from at least one of copper indium diselenide, gallium arsenide, and cadmium telluride.

3. The method of claim 1, wherein the thin film structure comprises the photovoltaic absorbent layer sandwiched between a substrate and a confinement layer, the confinement layer being substantially transparent to the laser beam.

4. The method of claim 3, wherein the thin film structure further comprises a molybdenum layer between the substrate and the photovoltaic absorbent layer.

5. The method of claim 3, wherein the confinement layer is made of glass.

6. The method of claim 1, further comprising scanning the laser beam across a specific region of the thin film structure.

7. The method of claim 6, wherein the scanning comprises moving the thin film structure using an X-Y stage.

8. The method of claim 6, wherein the scanning comprises using a movable mirror to scan the laser beam across the thin film structure.

9. The method of claim 1, wherein the pulsing comprises generating a series of laser beam pulses having a duration of approximately 5 nanoseconds.

10. The method of claim 9, wherein the series of laser beam pulses comprises at least 20 pulses.

11. A system for fabricating thin film photovoltaics, the system comprising:

a thin film structure comprising a photovoltaic absorbent layer covered by a confinement layer;

a laser generating a laser beam that travels along an optical path to hit the photovoltaic absorbent layer by passing through the confinement layer, the confinement layer being substantially transparent to the laser beam;

wherein the confinement layer confines a laser induced plasma plume and creates a localized high-pressure condition for the photovoltaic absorbent layer.

12. The system of claim 11, wherein the laser beam is pulsed to create localized rapid heating and cooling of the photovoltaic absorbent layer.

13. The system of claim 11, wherein the photovoltaic absorbent layer comprises at least one of a copper indium diselenide layer, a gallium arsenide layer, and a cadmium telluride layer.

14. The system of claim 11, wherein the thin film structure further comprises a substrate, the photovoltaic absorbent layer being sandwiched between the substrate and the confinement layer.

15. The system of claim 14, wherein the thin film structure further comprises a molybdenum layer between the substrate and the photovoltaic absorbent layer.

16. The system of claim 11, wherein the confinement layer is made of glass.

17. The system of claim 11, wherein the laser beam is scanned across a specific region of the thin film structure.

18. The system of claim 17, further comprising an X-Y stage for scanning the target relative to the laser beam.

19. The system of claim 17, further comprising a movable mirror for scanning the laser beam across the thin film structure.

20. The system of claim 11, wherein the laser is a neodymium-doped yttrium aluminum garnet (Nd:

YAG) laser.