Aluminum oxide passivation and damage removal for solar cells
The present application provides effective and efficient structures and methods for the formation of solar cell base and emitter regions and passivation layers using laser processing. Laser absorbent passivation materials are formed on a solar cell substrate and patterned using laser ablation to form base and emitter regions. Laser damage to the solar cell substrate is removed using an etch.
1. A method for making solar cell, comprising:
depositing an undensified doped laser absorbent aluminum oxide passivation layer on a surface of a solar cell crystalline silicon substrate using atmospheric pressure chemical vapor deposition, wherein the deposition process is performed at a deposition temperature less than 450° C., said undensified doped laser absorbent aluminum oxide passivation layer having a doping opposite said solar cell crystalline silicon substrate;
patterning said undensified doped laser absorbent aluminum oxide passivation layer using laser ablation, wherein said laser ablation has a wavelength in the infrared to ultraviolet range;
etching said solar cell crystalline silicon substrate in said laser ablation pattern and removing a layer from said solar cell crystalline silicon substrate; and
annealing said crystalline silicon solar cell substrate to form diffused solar cell doped regions corresponding to said patterned undensified doped laser absorbent aluminum oxide passivation layer.
2. The method of claim 1 , wherein said doped laser absorbent passivation layer is an metal rich doped laser absorbent passivation layer.
3. The method of claim 1 , wherein said doped laser absorbent passivation aluminum oxide layer has a thickness in the range of 10 to 50 nm.
4. The method of claim 1 , wherein said laser ablation has a pulse width in the range of 1 to 100 nanoseconds.