A research team led by Erkan Aydin and Stefaan De Wolf from the KAUST Solar Center, along with co-authors from Turkey, the Netherlands and Spain, has presented an overview on the process of stopping damage from occurring to devices during the creation of transparent electrodes, particularly for a technique known as sputtering.
Damage from adding electrical contacts to sensitive semiconductors, including perovskites, can be mitigated using a buffer layer and optimized deposition. The new review gives a comprehensive overview for the origin and mitigation strategies for this technological problem.
Sputtering works by placing the target semiconductor into a vacuum chamber and surrounding it in plasma. When an electric field is created between the target and the cathode made of the material to be sputtered, the fast-moving plasma ions transfer atoms/molecules from one to the other.
This technique is particularly useful for creating low resistivity and high transparency thin films of transparent conductive oxides (TCO), such as indium tin oxide (ITO).
However, the high kinetic energy of the ions can damage the semiconductor target. This degradation is severe enough to be seen using optical and electron microscopes, and leads to, for example, poorer device operation, lower maximum power output in solar cells and higher leakage current in LEDs.
â€œThis is a common problem for many optoelectronic devices, but there is no universalized solution to mitigate it,â€ says Aydin.
Aydin and colleagues reviewed strategies for mitigating this damage, in particular using a buffer layer between the semiconductor and the electrode. â€œAs a rule of thumb, buffer layers should be able to tolerate the particle damage during the sputtering process, while also functioning electronically and being optically transparent,â€ explains Aydin.
The co-authors summarize the strengths and weaknesses of different buffer materials and their suitability for different optoelectronic applications. They also compare numerous techniques for creating the buffer and give an overview for developing damage-free deposition of TCOs on optoelectronic devices in future.
â€œWith this comprehensive review, we elaborate the problem from multiple aspects and give the readers a basic understanding of the issue and offer some cross-disciplinary learnings,â€ says Aydin.