Application of non-contact quantum efficiency measurement for solar cell fabrication process insights

Abstract

We demonstrate the application of non-contact external quantum efficiency (EQE) measurements as potential in-line inspection for solar cell mass production. The technique, based on electroluminescence excitation spectroscopy (ELE), is several times faster than conventional contacted EQE measurements, and enables on-the-flight contactless assessment of spectral response. To simulate a manufacturing environment, EQE of a batch of 200 bifacial PERC solar cells are investigated. This allows statistical analysis of the interplay between fabrication process conditions, cell current–voltage characteristics and results from other in-line inspection tools. The study shows that non-contact EQE can be used to detect variation in POCl3 diffusion and PECVD processes at cell level and without direct contact to the device. It is also possible to predict EQE on passivated, non-metallized diffused wafers. This provides powerful information in predicting end-of-line cell parameters, as well as to sort and remove low performing wafers prior to printing to eliminate metal paste wastage.