Chalcogenide thin film repair for efficient photovoltaic conversion

Recently, researchers from Qingdao Institute of Bioenergy and Processes, Chinese Academy of Sciences (QIBEP), in association with Qingdao University of Science and Technology (QUST), revealed the potential chemical side reactions of chalcogenide in a fatty amine environment in the formamide and formamidine systems, and further proposed the research results of ammonia for post-repair of formamidine-based chalcogenide films.

Chalcogenide solar cells are an emerging photovoltaic technology, and after more than a decade of development, the photoelectric conversion efficiency has been comparable to that of silicon cells, which is considered to be the most promising new generation solar cell technology for commercialization. How to facilitate the large-scale preparation of high-quality chalcogenide thin films is one of the challenges faced in the commercialization process.

Researchers have studied the existence of addition-elimination reactions (also called transimine reactions), ion-exchange reactions and hydrolysis reactions of aminomethylamine iodide in an amine gas environment. It was found that the main product of the transimine reaction was ammonia gas. Therefore, the choice of ammonia gas as post-repair gas can effectively avoid the influence on the material composition. At the same time, they realized the efficient repair of amidine-based chalcogenide films by further regulation of temperature and pressure, which enhanced the film uniformity and consistency.

The chalcogenide solar cells prepared by this repair technique achieved a maximum photoelectric conversion efficiency of 23.21% and a module efficiency of more than 20%. This research has constructed the chemical basis of the ammonia-based gas post-repair calcium titanite thin film technology. In addition, the process is compatible with the current commercial coating process and easy to scale up, which is expected to accelerate the industrialization of chalcogenide solar cells.