Scientists at Oxford and the Italian Institute of Technology (IIT) have gained new insight into how exactly organic-inorganic perovskite solar cells absorb light. In the study published in Science, the researchers identified effective carrier diffusion as an important parameter that affects the solar cell efficiency.
According to the Italian Institute of Technology, this is the first study that reveals the photophysics mechanisms of perovskite solar cells. The study was carried out by by Annamaria Petrozza, a researcher at the Center for Nano Science and Technology (CNST) of the IIT in Milan and Henry Snaith, a researcher at the University of Oxford. This October, an article titled “Electron-Hole Diffusion Lengths Exceeding 1 Micrometer in an Organometal Trihalide Perovskite Absorber” (see footnote) was published in Science.
A perovskite structure is any material with the same type of crystal structure as calcium titanium oxide (CaTiO3). Perovskites take their name from this compound, which was first discovered in the Ural mountains of Russia by Gustav Rose in 1839 and is named after Russian mineralogist L. A. Perovski. Synthetic perovskites have been identified as possible inexpensive base materials for high-efficiency commercial solar cells—perovskite solar cells showed a conversion efficiency of up to 15%, and can be manufactured using the same thin-film manufacturing techniques as that used for thin film silicon solar cells.
However, there are still many unanswered fundamental questions about the basic physics of perovskite solar cells, including those related to the processes of charge generation and transport within the crystal upon interaction with light (optoelectronic processes), which are the basis of the device operation. The work of IIT researchers sheds some light on those questions.
“This investigations shows that in the material that we have optimized the chemical composition, the photogenerated charges can travel for distances greater than 1 micrometer in the device, a huge distance and if the prospect that the world of nanotechnology. This leads to the consideration that with a proper design of the perovskite crystals can be realized a solar device high conversion efficiency, simple and inexpensive at the same time,” said Annamaria Petrozza.
“Provided that the stability of the solar cells-based perovskites can be improved we will witness the emergence of a competitor for silicon that will ultimately lead to low-cost production of solar energy. This will break down the paradigm in which many now believe that it is not possible to combine cheap, durable, highly efficient photovoltaic devices,” said Henry Snaith.
Stranks SD, Eperon GE, Grancini G, Menelaou C, Alcocer MJ, Leijtens T, Herz LM, Petrozza A, & Snaith HJ (2013). Electron-hole diffusion lengths exceeding 1 micrometer in an organometal trihalide perovskite absorber. Science (New York, N.Y.), 342 (6156), 341-4 PMID: 24136964
