An Optical Imaging Method for High-Accuracy Solar Cell Area Measurement

Area measurement often represents a significant source of uncertainty in the efficiency of research-scale photovoltaic devices. This is particularly the case when devices are very small, as typically occurs with organic and other next-generation thin-film technologies. We describe an optical method for high-accuracy area measurement of solar cells with dimensions down to 1 mm x 1 mm and up to 160 mm x 160 mm. The method incorporates distortion correction and can handle devices of arbitrary shape, as well as superstrate devices where the active area is not at the surface of the sample. Sources of error in the method are analyzed, and the total uncertainty is shown to be only +/- 0.43% (k = 2) for square devices 1 mm in size. The method, therefore, almost eliminates area uncertainty as a factor in the efficiency measurement. We validate the accuracy of the method with measurements of known areas on a calibrated line grid.