A study of improvement of HJT solar cells by electro-thermal processing

Improvement of amorphous silicon/crystalline silicon heterojunction solar cells (HJT cells) by electro-thermal processing with the injected current greater than the short-circuit current (Isc) of the cells has been investigated. The results showed that, for the cells with a base efficiency level of 22.5% and an area of 244.32 cm2, forward current injections of 30-80 A yielded -0.60%abs efficiency gain on average, which was almost twice that by a 10 A injection. The improvement was mainly attributed to increased open-circuit voltage (Voc) and fill factor (FF). The lower the initial value of Voc or FF, the greater the increase was, and Isc was rather stable throughout the electro-thermal processing. Higher temperature and greater current are believed to favor the kinetics of the process. Light-thermal processing of HJT cells under electric field conditions of open-circuit, short-circuit, forward-voltage bias, and reverse-voltage bias were carried out. The results indicated that changes in the electric field do not affect the improvement of HJT cells by the light-thermal processing. It is encouraging that no considerable contact damages were found on the HJT cells electro-thermally processed in stacks, while the improvement was well kept, demonstrating the potential applicability of the electro-thermal processing for HJT cells on a production scale.