STABILIZATION OF MINORITY CARRIER LIFETIME IN PERC STRUCTURED SILICON SOLAR CELL

Abstract

This paper reports on the regeneration of the minority carrier lifetime in passivated emitter and rear cell (PERC) structured silicon solar cells. It is observed that minority carrier lifetime in the cells can degrade, recover and then stabilize with illumination level of ~1 sun (1000 W/m2) at 80oC. The exposure to ~1 sun illumination at 80oC enables the release of H from B-H bonds at ~1.3 eV energy to supplement the interstitial H in Si to passivate the B-O defects responsible for the minority carrier lifetime instability. Passivation of these B-O defects is therefore, dependent on temperature and time, hydrogenation and high carrier injection level. It was interesting to note that sequential process or single regeneration step led to same conclusion that minority carrier lifetime in a p-type PERC cell first degrades, due to B-O complexes, recovers and then stabilize with time. There is therefore, no need to degrade the cells in a separate step in order for regeneration to occur, because regeneration encompasses the three states: degradation, recovery and stabilization.