Studies on Copper Front Electrode for Si-based Solar Cell

Abstract

Of the rapid development in the world today tradition fossil fuel were reduced with mining The application of green energy become the global trend gradually Solar cell is one of the most popular alternative energy so more details about manufacturing solar cells should be developed stringently The aim of this study is to construct ohmic contact between front electrode and Si-based solar cell by two Newly-invented low-cost paste and high/low temperature sintering process In order to develop a low-cost high-conductivity copper front electrode to replace the traditional silver front electrode which is high-cost and with Pb inside This study uses self-made paste to screen printed on polycrystalline Si solar cell which has already finished the deposition of anti-reflection coatings and back Al electrode In the high temperature firing process paste was first screen printed on silicon substrate then two-step firing process was applied In the first firing stage the atmosphere was in air PbO-based glass frit etched the ARC and Ag recrystallized at the interface of Si constructing the ohmic contact The second stage was in reducing atmosphere In this step CuO reduced to Cu and Pb will volatile due to the interactions between Ag H2 and PbO-based glass frit reach the environmental protection goal of Pb free During low temperature firing stage using self-made CucoreAgshell powder to make high solid content paste then screen printing the fine line on laser-opening H-pattern silicon substrate and applying firing process Because the silver coverage is more than 90% and silver nanoparticles start to melt at 200℃ This mechanism can not only prevent copper from oxidized but enhance the conductivity TEM EDS SEM four-point probe and transmission line model were employed to analyze the results after each process By experiment and analysis reaction mechanism in each stage was surmised and it was also proven that ohmic contact for front electrode could be obtained In high temperature firing system the lowest specific contact resistivity was 0 003Ωcm2 and the lowest resistivity of front electrode measured was 4 5×10-6 Ωcm and the efficiency of solar cell is about 9 3% And in low temperature firing system the lowest specific contact resistivity was 0 004Ωcm2 and the lowest resistivity of front electrode measured was 7 5×10-6 Ωcm and the efficiency of solar cell is about 10 2% Our research finally develop a low-cost high-conductivity copper front electrode for solar cell

Date of Award	2015 Nov 20
Original language	English
Supervisor	Wen-Shi Lee (Supervisor)