Ajou's professors develop flexible and highly efficient solar cells  

[16.08.23]

A team of Professor Jae Jin Lee and Professor Joon Seok Heo from Ajou University (both in the Department of Electrical and Computer Engineering) succeeded in developing ultra-light and highly efficient solar cells based on GaAs. The team used the Metalorganic Chemical Vapor Deposition (MOCVD) technology in developing high-grade solar cell wafers and a new combination of p-type electrode structure, etc.

Their research findings were included in The Scientific Reports published in late July by Nature. According to the team, the thin film-type solar cell it developed is easier to commercialize for unmanned aircrafts and hand-held electronic devices, etc. thanks to high efficiency, flexibility, and lightness.

There have been active research activities involving inorganic materials, because flexible solar cells commonly made from organic materials are priced lower, but not efficient enough. The research team addressed the issue by using GaAs, a representative inorganic material and preferred in reliability and energy conversion efficiency, etc. The newly developed solar cell adopts a relatively simple Epitaxial Lift-off (ELO) process utilizing the stress of metal deposed on flexible boards and has a highly efficient n-on-p structure. The ELO process, a common way of making GaAs-based flexible solar cells, deposes semi-conductor elements onto a flexible board by separating them in the shape of thin films after the elements are formed on a hard board.

A technical challenge regarding the flexible n-on-p structure solar cell is that its p-type electrode is melted down by etching solution such as hydrofluoric acid during the relevant process. The research team made a breakthrough by developing and adopting the p-type electrode that is not dissolved by etching solution and has low resistance.

The team then made flexible GaAs-based solar cells by applying the newly developed p-type electrode to epi wafer – a process of adding semi-conductor properties to a GaAs-based board – after it is formed on MOCVD. The new cell has a global level of energy conversion efficiency with 22.08 percent and is strong in flexibility and lightness. The hard board used in the process can be recycled, which can dramatically reduce the manufacturing costs. 

Seong Hyeon Moon (doctoral course of the Department of Electrical and Computer Engineering) participated in the related paper as the first author and the research was conducted with the support of the Energy Technology Development Project carried out by the Korea Institute of Energy Technology Evaluation and Planning, the Priority Research Institutes Project carried out by the Ministry of Education, and the General Researcher Support Project (new research) carried out by the Ministry of Science, ICT, and Future Planning.

< A photo of the GaAs-based solar cell developed by Ajou's research team. It has a highly efficient n-on-p structure thanks to a new combination of p-type electrodes that can endure the ELO process.>