Russian scientists investigate quantum dot solids for PV applications

As the development of solar cells based on material alternatives to silicon continues to gather pace, the emerging technology of quantum dots (QD) is attracting growing interest. The latest research in this field, conducted by scientists at Russia’s National Research Nuclear University Moscow Engineering Physics Institute (MEPhI), looks into the charge and energy transfer in condensates of quantum dots.

Discussing the structure of semiconductor QD solids, optical and spectral properties, charge carrier transport, and photovoltaic applications, the research, titled Optoelectronic Properties of Semiconductor Quantum Dot Solids for Photovoltaic Applications and published in the Journal of Physical Chemistry Letters points out that the correct selection of a layer sequence involving QDs with different size, composition, and ligands can be used to absorb sunlight over a broad spectral range, leading to inexpensive and efficient photovoltaic devices.

Given that quantum dots consist of dozens of atoms, which are characterized by modification of their properties such as optical and electronic, and the number of which depends on the difference of energy levels of electrons and holes, consequently affecting the range of absorbed light, the scientists have shown that the distance between adjacent nanoparticles and surface ligands influences greatly electrostatic interactions between QDs and, hence, charge and energy transfer.

“The published work shows that the charge and energy transfer in condensates of quantum dots can be described in a relatively simple way. This considerably simplifies the task of theoretical modeling of charge carrier transport needed to optimize characteristics of optoelectronic devices based on quantum dots,” says one of the authors, Professor in MEPhI’s Department of Condensed Matter Physics, Vladimir Nikitenko.

Another breakthrough for this type of technology happened late last year, when scientists at the U.S. Department of Energy’s National Renewable Energy Laboratory (NREL) developed a solar cell using colloidal quantum dots, which achieved 13.4% conversion efficiency, setting a new world record.