Exponential growth in both interest and attention paid to the organic-inorganic metal halide perovskites materials have spiked undeniable concern of late. The outstanding properties possessed by these materials carry all the credit. These properties, including: long exciton diffusion length, strong absorption coefficients, low cost, ease of Synthesis and environmental-friendliness have led to great advancement in perovskite solar cells such as improving the power conversion efficiency from around ten percent in the early years of this decade to about twenty percent at present. Recent studies have shown that the quality and morphology of the perovskite films are crucial to its photoelectric properties and that they directly influence the performance of the resultant perovskite solar cells. Even though several deposition techniques have been proposed for synthesis of the perovskite light-absorption layers, great difficulties are still being encountered in the bid to fabricate perovskite films with both satisfactory coverage and uniformity over a large area.
Researchers led by Professor Meicheng Li at the State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources in North China Electric Power University developed a novel process route based on direct current reactive magnetron sputtering in the preparation of the CH3NH3PbI3 film. They aimed at presenting a complete approach for the fabrication of large area perovskites solar cells with the advantages of easy control, economical and requiring less use of toxic reagents but with diverse potential applications. Their research work is now published in Solar Energy Materials & Solar Cells.
The research team began by fabricating the lead oxide film on an FTO-glass substrate coated with a nanocrystalline rutile titania by using a pure metallic lead target in an argon-oxygen mixture. They then converted the prepared lead oxide film to CH3NH3PbI3 through the sequential reactions setup in isopropanol solution of CH3NH3I. Eventually, the research team fabricated solar cells of a complex structure that employed nanocrystalline rutile titania as the contact layer of the photovoltaic devices.
The authors were able to observe that the as-prepared perovskite film exhibited a surface morphology of high uniformity and excellent coverage over a large scale. Also the crystal grains were seen to reach the size of up to 600 nm, which is beneficial to extract photo-generated electrons more effectively and prepare the perovskites solar cells at low temperature.
The new approach employed in their study is technically spin-coating-free for the formation of large area CH3NH3PbI3 film and exhibits advantages ranging from easy process control, economical all the way to less use of toxic reagents. Of crucial importance, it is expected that this novel technique will be applied for the synthesis of perovskites solar cells or other thin-film devices and thus entails potential applications and practical significance.
Zhirong Zhang, Meicheng Li, Wenjian Liu, Xiaopeng Yue, Peng Cui, Dong Wei. CH3NH3PbI3 converted from reactive magnetron sputtered lead oxide (PbO) for large area perovskite solar cells. Solar Energy Materials & Solar Cells, volume 163 (2017) pages 250–254.
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