Review of Conductive Copper Paste for c-Si Solar Cells

In the photovoltaic industries, the main technique of metallization is screen printing with silver pastes, due to its simple and quick process.However, the high price of silver paste is one of the barriers to the producing of low cost solar cells.Consequently, a primary target in photovoltaic research is to reduce consumption of silver paste or substitute silver with other lower cost materials.As a proper candidate, copper has been extensively investigated for that purpose by many institutes and companies, since it is less expensive than silver with similar conductivity.The plating technique has been actively researched to apply copper as a contact for solar cells.However, copper paste, which was originally developed for integrated circuit applications, has been recently attracted attention.Initially, copper paste was applied for a low temperature annealing process since copper tends to oxidize easily.Recently, a firing type copper paste was also developed which involves coating of the copper particles with a barrier layer.This paper reviews recent developments of copper pastes for the application to solar cells, and its appropriate annealing conditions for better electrical properties.Also, the light I-V characteristics of copper paste on the solar cells reported in the literature are summarized.The 20.7% of the conversion efficiency of a PERT (passivated emitter and rear totally diffused) structure solar cell demonstrates the potential of copper paste as a promising future metallization material.