Lowering firing temperature of a p-type passivated emitter rear contact Si solar cell via current injection

Abstract

Effective contact formation during low-temperature firing with applied current was investigated in this study. The screen-printed electrode was fired using rapid thermal annealing and contacted by etching the passivation layer and forming Ag crystallites. In our previous study, we proposed a method for reducing this contact resistance from 5 to 1 mΩ cm2 by applying a current during the firing of a phosphorous-doped (P-doped) n+ emitter in a p-type Si wafer without a silicon nitride (SiNx) passivation layer. According to the results, current application during the firing of Si solar cells should reduce the required firing temperature. Herein, a current (3 A) was applied between the screen-printed electrode and P-doped n+ emitter in a p-type Si wafer with an SiNx passivation layer during low-temperature firing from 350 to 600 °C. The major effects of the proposed methods were a reduced contact resistance and enhanced of SiNx etching. Cross-sectional scanning electron microscopy images at different firing temperatures demonstrated that current injection during firing promoted the etching of the SiNx layer. Additionally, the method of current injection with low-temperature firing proposed in this work resulted in a device with a solar cell efficiency of 19.0%, which is similar to the efficiency of a reference cell fired at a higher temperature.