Thermography Techniques

Local pre-breakdown sites in solar cells can be studied by lock-in thermography (LIT). Three new LIT techniques are proposed and demonstrated here, which are TC-DLIT for studying the local temperature coefficient of pre-breakdown sites, Slope-DLIT for measuring the normalized local slope of the I–V characteristics, and MF-ILIT for imaging the local carrier multiplication factor. First results on multi-crystalline silicon cells show that the pre-breakdown mechanism cannot completely be described by the conventional impact ionization and internal field emissionmodels. Copyright # 2008 JohnWiley & Sons, Ltd. key words: crystalline solar cells; pre-breakdown; lock-in thermography; internal field emission; impact ionizatio