Back contact electrodes allow avoiding shading and transmission light losses caused by a top electrode of a solar cell. Up to now, the champion silicon solar cells are made in this configuration.
Back contact concepts are particularly interesting for solution- processable thin-film photovoltaics such as perovskite solar cells. On one hand having the deposition of the perovskite layer on the pre-fabricated back-plane allows to avoid a number of processing issues encountered in the fabrication of classical planar configuration solar cells. On the other hand, due to the micron and sub-micron range charge diffusion length in perovskite material, the gap between rear electrodes has to be of similar dimensions or smaller in order to collect the charges efficiently. That creates a risk of short circuit between the positive and negative electrode.
To face this issue, our group as a first in the world proposed a novel Quasi Interdigitated Back Contact architecture. In this configuration one of the rear electrodes is sitting on the
flat base electrode and the electrodes are disconnected from each other by an insulating layer. In this case, no matter how small and how close to each other the rear electrodes are, the risk of short circuit is eliminated by the insulating layer. Our micro size rear electrodes are manufactured via photolithography technique in a clean room environment.
Our current research in the back contact area focuses on developing new techniques of manufacturing nano size quasi – interdigitated electrodes (e.g. e-beam lithography) and improving their design by varying the ratio and changing the shape of the electrodes. We also perform in-situ measurements of the perovskite layer during various post treatment processes as well as implement antireflection and sealing coatings.