Development and Implementation of In-line Characterization Methods for Roll-to-Roll Production of Thin-Film Solar Modules

Abstract

This report emphasizes the importance of implementing quality control methods in the production machines at HyET Solar for assessing the quality of deposited materials. The focus is on two key steps: the deposition of the front transparent conductive oxide (TCO) layer and the deposition of silicon layers. Models were developed to characterize the quality of the TCO layer, including layer thickness, carrier concentration, and mobility of the electrons. A Drude model-based approach was chosen for in-line implementation. The sheet resistance of the TCO layer was measured using an improved tool, by enhancing its robustness and accuracy. To assess the quality of the deposited silicon layers, a non-contacting capacitive device was developed and calibrated (to measure the spatial gap between the photovoltaic layer and the device). Results showed that the Drude model fitting provided sensible results for carrier concentration and mobility with the former having a better correlation than the latter, with the standard Hall effect measurements. The results from the optical thickness model showed overestimation of values as compared to the scanning electron microscopy (SEM) results. The electrical sheet resistance values correlated well with Hall effect measurements than the optically obtained sheet resistance values. The calibrated non-contacting capacitive device demonstrated its ability to measure opto-electrical properties of the silicon layers, accurately. This research contributes to enhancing the efficiency and reliability of roll-to-roll production process of thin-film solar modules.