Investigation of Passivating Layers in c-Si Solar Cells Using a Corona Charging System
R. Liu (TU Delft - Electrical Engineering, Mathematics and Computer Science)
O. Isabella – Mentor
SGM Heirman – Graduation committee member
Dimitris Deligiannis – Graduation committee member
Arno H.M. Smets – Graduation committee member
Jianning Dong – Graduation committee member
A. R. Mor – Graduation committee member
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Abstract
There are two existing surface passivation principles. Passivation of unsaturated Si bonds is called chemical passivation. Surface passivation can also be achieved by shielding the minority charge carriers from the semiconductor interface by means of an electric field. This method is referred to as field-effect passivation.
To test the effect of the field-effect passivation provided by the passivation layer, fixed charge density is the most important parameter. Delft Spectral Technologies (DST) developed a new Corona Charging System used to measure this value. It integrates the corona charging and Kelvin probe into one box. As the corona charging system is still in prototype, several improvements are made to the system, especially the improvements of the charge uniformity. In the thesis four different charging plans are compared to acquire the best charge uniformity.
Several passivation layers are tested with the DST corona charging system to measure their fixed charge density, including Atomic Layer Deposition (ALD) Al2O3, Plasma Enhanced Chemical Vapor Deposition (PECVD) SiNx, Low Pressure Chemical Vapor Deposition (LPCVD) poly-Si. Morphology of the c-Si bulk influence on the fixed charge density in ALD Al2O3 has also been studied.
Finally, research on the charge decaying properties has been done, to find out the stability of the corona charges on different passivation layers.