Stella Yu : Publications

Learning Quality Rating of As-Cut mc-Si Wafers via Convolutional Regression Networks
Matthias Demant and Patrick Virtue and Aditya Kovvali and Stella X. Yu and Stefan Rein
IEEE Journal of Photovoltaics, 2019
Paper

Abstract
This paper investigates deep convolutional neural networks (CNNs) for the assessment of defects in multicrystalline silicon (mc-Si) and high-performance mc-Si wafers for solar cell production based on photoluminescence (PL) images. We identify and train a CNN regression model to forecast the I–V parameters of passivated emitter and rear cells from given PL images of the as-cut wafers. The presented end-to-end model directly processes the PL image and does not rely on the human-designed image feature. Domain knowledge is replaced by a model based on a huge variety of empirical data. The comprehensive dataset allows for the evaluation of the generalizability of the model with test wafers from bricks and manufacturers not presented in the training set. We achieve mean absolute prediction errors as low as 0.11\%abs in efficiency for test wafers from "unknown" bricks, which improves handcrafted feature-based methods by 35\%rel at simultaneously lower computational costs for prediction. Samples with high prediction errors are investigated in detail showing an increased iron point defect concentration."

Keywords
convolutional neural network (CNN), densely connected neural network (DenseNet), high-performance multicrystalline silicon (HPM-Si), machine learning, material quality, multicrystalline silicon (mc-Si), passivated emitter and rear cell (PERC), photoluminescence (PL), rating, regression, solar cell.