MAPPING OF THE LOCAL SPECTRAL PHOTOCURRENT OF MONOLITHIC SERIES CONNECTED a-Si:H P-I-N THIN FILM SOLAR MODULES

摘要

For the up-scaling process of a-Si:H p-i-n modules, measurement equipment is necessary which helps to characterize the uniformity of the different sub-layers of thin film modules as well as the quality of the cell interconnections. For this goal, a measurement tool was developed and realized which is able to map locally the spectral photocurrent of large thin film modules (1.4 m~2 module area) automatically. It could be shown that the mapping results of the Quantum Efficiency QE is very reproducible and stable. The relative standard deviation of the reproducibility is less than ±1% for this measurement method. As the distance between the light spot and the contact bars is found to be important, a precise electromechanical 3-axes control system was developed to move the light spot together with the contact bars. The resulted QE mapping plots, e.g. at three different characteristic wavelengths, give insight into the homogeneity of the sub-layers (e.g. p-layer, back contact and TCO). Also, local defects, such as pin-hole shunts, contamination or laser scribing defects, may be located and identified. By the use of the developed automatic backlight system the QE mapping will also be able to characterize tandem thin film large-area modules. In an R&D environment, this QE mapping results are very helpful to improve several module production process steps. The method is suitable for the quality inspection of module samples in a production line.