Improvements in the acquisition of daylight Electroluminescence Images using high speed cameras: comparison of square and sinusoidal waves excitations

Abstract

Electroluminescence (EL) imaging is a very powerful technique for the identification of defects in Silicon solar cells and panels. Daylight Electroluminescence (dEL) has emerged recently, aiming to avoid the need to perform the EL images on dark environments, which complicates the measurements and limits the number of panels to be inspected. In this work we present a procedure to obtain dEL images by using sinusoidal or square excitations and high speed InGaAs cameras, working in asynchronous mode between excitation and signal capture. We subsequently apply post-processing techniques based on both frequency and time domain analyses to assess the quality of the images by quantifying the signal-to-noise ratio arising from both analyses. We captured a stack of dEL images using two InGaAs cameras capable of acquiring at speeds of up to 60 and 600 frames per second. Our results demonstrate the promising potential of the proposed dEL method, as the post-processed image stack exhibits the same features as dark EL images obtained using the same InGaAs cameras. Notably, this stack of dEL images can be obtained within a very short acquisition time, typically ranging from 100 to 200 ms, while maintaining good image quality.