Local doping using Laser Chemical Processing technology for advanced silicon solar cells

Australian National University, Fraunhofer Institute for Solar Energy ISE (GERMANY)

Local, heavily doped regions integrated into cell manufacturing processes can create high efficiency wafer-based silicon solar cell structures.

This project aims to advance a novel doping method, Laser Chemical Processing (LCP) technology, to create high efficiency, low cost cells.

ANU will:
• Develop high-quality localised doping (with suitable electronic quality, doping profile, uniformity and contact resistance)
using an industrially applicable LCP process with optimised laser doping parameters.
• Demonstrate at least 20% efficient cells with LCP doping on the front side, using optimised, industrially feasible LCP
• Demonstrate front and rear LCP doped cells with efficiency of at least 20%.

LCP technology represents a modification of waterjet technology, where a laser beam is guided in a hair-thin liquid jet to a silicon sample. In this project, the laser light is trapped in the liquid jet (a doping medium such as phosphoric acid) via total internal reflection and the laser focus plane can be maintained over a distance of many centimetres. The flow of the liquid melts the silicon near the surface and dopant atoms from the liquid jet rapidly diffuse into the molten silicon. Upon removal of the laser power, the silicon solidifies, creating a locally doped region.

Key benefits of the technology (compared to existing ‘dry’ laser technology):
• Reduction in process complexity
• Direct plating of contacts, without the need for oxide removal (using hydrofluoric acid)
• Good adhesion of contacts
• Reduced risk of possible shunting

Successful project outcomes will significantly accelerate commercial application of the technology, which will result in improved cell conversion efficiencies.

Fact Sheet: Local doping using Laser Chemical Processing technology for advanced silicon solar cells (PDF 318KB)