The concerns and worries over environmental pollution and energy exhaustion have made human beings rethink utilizing recyclable green energy. The sun, the oldest energy source on earth, has reentered people's vision. In several billion years, the sun is an inexhaustible ideal source of energy with broad prospects for exploitation.
Solar energy can be utilized through photothermal, photoelectric and photochemical approaches. Solar photovoltaic cells can directly convert light energy into electricity and is one of the most convenient ways to utilize solar power, though its wide use is hampered by some unsolved problems. One of the problems is that though monocrystalline silicon cell is highly efficient, the high cost prevents it from large scale production and application. Therefore, the search for an efficient and inexpensive substitute material has become a new objective in solar photoelectric studies.
Recent research findings suggest materials with perovskite crystals have high photoabsorption coefficient and long carrier transmission distance, and is highly applicable in fields such as photoelectric, laserable and luminescent materials. The photoelectric conversion rate of the solar perovskite cell certified by National Renewable Energy Laboratory of U.S. Department of Energy has reached 20.1%, a rate near monocrystalline silicon cell, which makes it possible for the appearance of a new material of photoelectric cell.
Despite the prospect of the application of monocrystalline perovskite in solar photoelectricity, the perovskite in current solar cells and other photoelectri devices mostly exist in the form of microcrystalline. These tiny microcrystallines have many deficiencies such as crystalline grains and pores highly sensitive to vapor, atmosphere, heat and ultraviolet, which leads to the combination of carriers and reduced photoelectric conversion rate. The development of solar cells may be taken to a new level if this bottleneck problem could be solved.
To tackle this problem, the research team led by rof. Liu Shengzhong of School of Material Science and Engineering of Shaanxi Normal University used thermal crystallization process and has successfully grown the two-inch-sized supersize monocrystalline perovskite CH3NH3PbX3 crystals. It is the first monocrystalline perovskite crystal more than 0.5 inch ever reported. Their research findings indicate that, compared with polycrystalline films, solar cells made of single-crystalline perovskite crystal have a better photoelectric conversion rate, and more crystal intactness and less deficiency of monocrystalline device bring higher thermostability.
The research findings were published in Advanced Materials on August 6, whose editor-in-chief commented that "As large single crystalline materials form the basis for semiconductor, electronics and optoelectronic industries, this technique will bring high quality perovskite crystals into the market at lower costs. While such materials can certainly improve the performance of current products, they will explore and develop areas that were previously hampered by small microcrystalline materials."
Prof. Liu said, "This material can provide some special properties, for example semiconductor, so it can be used to make semiconductor devices and high-performance photoelectric devices. We expect supersize monocrystalline perovskite can be applied in fields of semiconductor, photoelectricity and solar cells to create more commercial value."
Text by Xiao Wei, Feng Wei
Photo by Zhang Li