Luminescence imaging for the detection of shunts on silicon solar cells

Abstract

Luminescence imaging is a non-destructive, fast, and versatile imaging method for spatially resolved solar cell and material characterization. In this paper, we investigate its ability to detect shunts on silicon solar cells. We give a detailed description of the relation between local junction voltage and local luminescence signal. This relation is important because shunts drain majority currents causing voltage drops across the surrounding series resistances and that way affect luminescence images. To investigate effects related to majority currents, we describe and apply a simulation model that allows the simulation of lateral voltage distributions on solar cells. This model, and a comparison to illuminated lock-in thermography, helps to discuss some practical aspects about shunt detection by luminescence imaging. We will discuss a procedure to distinguish between ohmic and diode-like shunts and finally present simulations and measurements showing that luminescence imaging is only weakly sensitive to shunts under the metallization. However, we also show its high sensitivity for remote shunts and propose a possible application where this high sensitivity could be especially helpful. 300 M. KASEMANN ET AL.Figure 7. ILIT (top) and PL (bottom) measurements of an intentionally shunted solar cell under open-circuit conditions. Shunts on grid lines are labeled by letters A-E in the ILIT image, while shunts between grid lines are labeled by numbers 1-7 in the PL image. Shunts appear as high values in ILIT and low values in PL imaging. The shunts have been introduced by laser firing

Early degradation of silicon PV modules and guaranty conditions

“…The excitation can be achieved by means of an injected current, which provokes an electroluminescence (EL) effect. The excitation can also be obtained by means of a radiation incident over the solar cell, in which case the light obtained is due to a photoluminescence (PL) effect (Kasemann et al, 2008).…”

Fusion of Thermal and Visible Acquisitions for Evaluating Production-borne Scratches and Shunts in Photo-Voltaic PV Cells

“…Even though emission intensity is affected by many physical properties such as surface recombination velocity and the recombination at defects, etc., Fuyuki, Kondo, Yamazaki, Takahashi and Uraoka (2005) considered that emission intensity will be proportional to the number of minority carriers, which is determined by the diffusion length. The shunt detection capabilities of luminescence imaging methods are investigated in Kasemann et al (2008) by relating the luminescence intensity to the local junction voltage. Localized shunts drain majority currents from its surroundings, which eventually leads to a drop in voltage across series resistances that connect shunts laterally to non shunted areas.…”

Lock-in and Heterodyne Carrierographic Imaging Characterization of Industrial Multicrystalline Silicon Solar Cells

“…Imaging techniques based on quasi-steady-state (dc) electroluminescence and photoluminescence (PL) are widely used for qualitative and quantitative characterization of silicon solar cells [1][2][3][4][5][6]. These types of imaging are extremely relevant for an estimation of the efficiency of solar cells using non-contacting methods [7,8].…”