IMAGING AND ANALYSIS OF PRE-BREAKDOWN SITES IN MULTICRYSTALLINE SILICON SOLAR CELLS

Abstract

We report on studies of the emission of light from industrial multicrystalline silicon solar cells under for- ward and reverse bias. Camera-based luminescence and dark lock-in thermography imaging techniques are used to study the spatial distribution of and energy dissipation at pre-breakdown sites. The pre-breakdown is associated with an in- crease in temperature and the emission of visible light. Three different breakdown types are distinguished by investigat- ing the local luminescence and dark lock-in thermography signal as a function of the reverse bias. Moreover, we show that specific areas characterized by recombination active fine dendritic lines also give rise to sub-band-gap luminescence. This luminescence has a broad wavelength distribution with a maximum at around 1550 nm. Studies of multicrystalline silicon solar cells with different interstitial oxygen concentrations and electron microscopic analysis suggest that this light emission is directly related to clusters of oxygen.