For the first time, the researchers presented a model that explains the main instability mechanism of perovskites – the materials of the future for solar cells. They demonstrated for the first time how an internal degradation mechanism affects the stability of perovskite-based solar cells – cells that are expected to be integrated into silicon solar cells and, later, also in light, semi-transparent cells for a range of other applications.
Producing solar cells from these materials is a simple process, which makes it possible to incorporate them in silicon solar cells, thereby substantially improving the exploitation of the sun’s energy and accelerating their implementation in the production of green energy
The research, led by doctoral student Sapir Bitton and Prof. Nir Tessler, was published in the prestigious journal Energy & Environmental Science. Its results are expected to accelerate the use of perovskites in devices used to convert energy, thereby dramatically enhancing the efficiency of existing silicon cells.
Perovskites are materials that have unique properties, including high efficiency rates during the conversion of light energy to electricity. These materials are less expensive than silicon as well as being flexible, light and transparent. Consequently, they are considered excellent candidates for the production of laser devices, photo-electrodes, light emitting diodes, and others – and especially solar cells. As a result of these advantages, research groups and companies are trying to develop perovskite-based solar cells. Solar cells are devices that convert solar energy to electric energy – green energy that is sustainable. Adding perovskite cells to the arsenal of solar cells will enable a much wider deployment of solar cells and their applications on various surfaces, such as windows, cars and clothing – which would expand human usage of solar energy and artificial light in our environment.
The main challenge confronting companies that develop these cells is the instability of perovskite. In their article in Energy & Environmental Science, the Technion researchers describe the reasons for this instability, which affects the efficiency of perovskite=based devices. One of the main reasons for this instability is ions (atoms carrying electric charges) that roam from the perovskite crystal to the rest of the device. Another reason is the reaction of these ions with other charges. Exposure to light, which is obviously required in solar cells, accelerates the roaming of the perovskite ions in the device, thereby gradually harming its performance already within the first hours of operation.
The article by the Technion researchers examines this phenomenon for the first time, using simulations and devices developed by the semiconductor industry to assess the impact of the ions and the reactions taking place in the device under various physical states. Bitton and Prof. Tessler don’t merely describe the device’s degradation mechanism; they offer a framework for curbing it. The roaming of ions is halted by controlling the energy levels of the materials that compose the device.
The research is supported by the Ministry of Science and Technology; the European Union (M-ERA.NET grants); the Adelis Foundation through the Grand Technion Energy Program; and the Ollendorf Minerva Center at the Technion. Sapir Bitton is an Ariane de Rothschild Scholarship recipient – a grant from the Rothschild Caesarea Foundation for outstanding women doctoral students.
