Rear surface passivation in buried contact solar cells

A range of rear surface structures have been developed and studied for the purpose of improving the performance of buried contact solar cells (BCSC). In particular, improved results are reported for the double grooved BCSC with oxidised p-type rear surface, with V/sub oc/ of 685 mV having been demonstrated. The importance of including an anneal treatment is clearly evident with open circuit voltages typically degrading 60 mV without its inclusion. Devices with the same structure but with a rear floating junction are also evaluated within the study and again the dependence on an anneal is evident for cells with low surface phosphorus concentration. In the highest voltage devices, the rear boron diffused grooves contribute almost 30% of the total device dark saturation current, with test devices achieving V/sub oc/ as high as 694 mV for a BCSC with the rear grooves replaced by photolithographically defined boron diffused contact regions.