Band gap engineering of hybrid organic-inorganic lead halide perovskites

Popov, K.

Автор: Kirill Popov
Сборник: The Kupcinet‐Getz International Science School for Undergraduate Students Summer 2014 Book of Abstracts
Тезисы
Год издания: 2014
Место издания: Feinberg Graduate School, Weizmann Institute of Science Rehovot, Israel
Первая страница: 27
Последняя страница: 27
Аннотация: Organic ammonium lead trihalides RNH3PbX3 (X=Cl, Br, I) are semiconductors with perovskite‐ type crystalline structure that are being intensely investigated as a light harvester used in photovoltaic devices. The band gap of these materials can be finely tuned in the range of 1.55 to 2.4 eV, by varying the organic cation and anion composition, which makes them suitable for application in both single‐junction solar cells and tandem solar cells with silicon as a low‐band gap layer. The efficiencies of organolead halide perovskite‐based solar cells have dramatically increased from 6.52% in the first report in 2009 to 19.3% today. Abundance and low cost of precursors as well as a variety of versatile fabrication techniques also make this organic ammonium lead trihalides system a very promising candidate for industrial application in the future. However, there are still basic scientific understandings which are not yet known and need to be explored and studied for this to happen. The first goal of this project is to clarify the mechanism of charge transfer in CH3NH3PbClxI3‐x. While being well‐known for its good conductance of both electrons and holes, it is unclear if there are other mechanisms of charge transfer such as ionic conductivity. I aimed to do so by first making an ohmic contact to the perovskite layer, which I succeeded to do by using Au as a contact, and then used impedance spectroscopy to inspect if ionic conductivity is present. The second goal was to characterize the band gap of CH3NH3Pb(I,Br)3 films prepared by dipping PbI2 and PbBr2 films in solutions containing various amounts of CH3NH3I and CH3NH3Br by transmittance and photoluminescence measurements. Obtaining the data on these materials helps to understand more about the thermodynamics of perovskite formation process and to optimize film fabrication. Band gap characterization of the films show that for 1h dipping times, the final composition of the film is controlled mostly by the concentrations in the solution. At the same time formation of lead iodide is found to be preferable for all solution compositions.
Добавил в систему: Попов Кирилл Вячеславович

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