NREL’s Ashley Marshall, Erin Sanehira and Joey Luther with solutions of the all-inorganic perovskite quantum dots, showing intense photoluminescence when illuminated with UV light. Photo: NREL.Scientists with the US Department of Energy's National Renewable Energy Laboratory (NREL) have, for the first time, discovered how to make perovskite solar cells out of quantum dots and shown how these solar cells can convert sunlight to electricity with an efficiency of 10.77%.
The scientists – Abhishek Swarnkar, Ashley Marshall, Erin Sanehira, Boris Chernomordik, David Moore, Jeffrey Christians and Joseph Luther from NREL, together with Tamoghna Chakrabarti from the Colorado School of Mines – report their work in a paper in Science.
As an integral part of developing these quantum dot perovskite solar cells, the researchers also discovered a way to stabilize at room temperatures the crystal structure of an all-inorganic perovskite material that was previously only stable at high temperatures. They found that the crystal phase of this inorganic material is more stable in the form of quantum dots.
Most research into perovskites has focused on a hybrid organic-inorganic structure. Since research into perovskites for photovoltaics began in 2009, their efficiency at converting sunlight into electricity has climbed steadily and now stands at more than 22%. Unfortunately, the organic component of these perovskites hasn't been durable enough to allow their long-term use in solar cells.
To solve this problem, NREL scientists turned to the nanocrystals known as quantum dots, specifically to nanocrystals of the perovskite cesium lead iodide (CsPbI3), in which cesium replaces the usual organic component. This could open the door to high-efficiency quantum dot optoelectronics that can be used in LED lights and photovoltaics.
The scientists synthesized the nanocrystals of CsPbI3 by adding a cesium-oleate solution to a flask containing a PbI2 precursor, and then purified the nanocrystals using methyl acetate as an anti-solvent to remove excess unreacted precursors. This step turned out to be critical to enhancing the stability of the nanocrystals.
The scientists found that these CsPbI3 nanocrystals were not only stable at temperatures exceeding 600°F but also at room temperatures and at hundreds of degrees below zero. In contrast, the bulk version of CsPbI3 is unstable at room temperature and converts very quickly to an undesired crystal structure.
The NREL scientists were able to transform these nanocrystals into a thin film by repeatedly dipping them into a methyl acetate solution, yielding a film with a thickness of 100–400nm. When used in a solar cell, this CsPbI3 nanocrystal film proved able to convert 10.77% of sunlight into electricity at an extraordinary high open circuit voltage. This efficiency is similar to that of quantum dot solar cells made from other materials and surpasses other reported all-inorganic perovskite solar cells.
This story is adapted from material from NREL, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.