But what does a perovskite-based solar cell look like?
Not to leave you wondering how a perovskite-based solar cell looks like, I would like to conclude my writing with a short explanation about them. Part of the information was again provided by Núria during our conversations, but the summary that follows is thanks to her written Master thesis introduction which she unselfishly shared with me and I am beyond grateful for that.
In order to obtain a functioning solar cell, we need an absorber and an emitter. As soon as the sun light is absorbed, electron-hole pairs are generated. This is possible due to the internal photoelectric effect. When the electron is excited into the conduction band, it abandons its location in the valence band, leaving a hole behind.
“When it comes to the perovskites and their connection to solar cells, it was found out that the perovskites can be used as absorbers and transport material”, explained Núria. “Nowadays, the perovskites-based solar cells are in general arranged in structure of thin-film layers where the absorber is sandwiched between an electron-donor and electron acceptor material”. You can see this on the figure below.
The structure shown above is a simple planar thin film cell. For the metallic contacts that extract carriers gold and FTO are used. FTO stands for fluorine-doped tin oxide. “The perovskite is used to absorb the sunlight and in-turn create electron-hole pairs, thus playing a crucial role in the structure” – elaborated Núria: “The perovskites can have a varying elemental composition obtained by using several combinations of anions and cations. This in return leads to the important advantage to tune the perovskites’ optical band gap and the wavelength of light absorption of the material, thus using a higher fraction of the sun light. With my work at EMIL I hope to use this property in my advantage and get insightful results that can help us increase the efficiency of the solar cells.”