On the assessment of CIGS surface passivation by photoluminescence

An optimized test structure to study rear surface passivation in Cu(In,Ga)Se₂ (CIGS) solar cells by means of photoluminescence (PL) is developed and tested. The structure – illustrated in the abstract figure – is examined from the rear side. To enable such rear PL assessment, a semi‐transparent ultra‐thin Mo layer has been developed and integrated in place of the normal rear contact. The main advantages of this approach are (i) a simplified representation of a rear surface passivated CIGS solar cell is possible, (ii) it is possible to assess PL responses originating close to the probed rear surface, and (iii) a stable PL response as a function of air exposure time is obtained. In this work, PL measurements of such structures with and without rear surface passivation layers have been compared, and the measured improvement in PL intensity for the passivated structures is associated with enhanced CIGS rear interface properties. magnified image Transmission electron microscope (TEM) bright field cross‐section image of the rear illuminated test structure fabricated for PL characterization. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)