Nondestructive local analysis of current–voltage characteristics of solar cells by lock-in thermography

By evaluating dark lock-in thermography images taken at one reverse and three forward biases, images of all two-diode-parameters J01, J02, n (ideality factor of J02), and Gp (the parallel Ohmic conductivity) of the dark current–voltage characteristic are obtained. A local series resistance is explicitly considered and may be provided as a series resistance image, e.g. resulting from luminescence imaging. The results enable a separate investigation of factors influencing the depletion region recombination current and the diffusion current, which is governed by the bulk lifetime. Local I–V characteristics of special sites may be simulated.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Dark current of all industrial solar cells (multi- and monocrystalline) flows inhomogeneous. ► For cell optimization, the local 2-diode parameters of the dark characteristic are needed. ► These are obtained by evaluating four lock-in thermography images taken at various biases. ► Procedure enables the calculation of realistic local current–voltage characteristics. ► The results of this procedure enable a detailed local analysis of the dark current losses.