For solar cells, the design is the same as that of double blade razors, that is, the two-step working mode is always better than one. Overlapping the two solar cells is a good design. The upper layer is a translucent material that can convert high-energy photons into electrical energy; The underlying material can convert low-energy photons. This allows more light energy to be converted into electrical energy.
So far, the complex technologies required for this process are mainly limited to the field of space or dense photovoltaic (CPV). This "laminated battery" is grown on a very expensive single crystal chip, so it is not conducive to large-scale production. EMPA - the research team led by Stephan buecheler and Ayodhya n. Tiwari of the thin film materials and photovoltaic Laboratory of the Swiss Federal Laboratory of materials science and technology has successfully realized the growth of laminated solar cells on polycrystalline thin films. This method is low-cost, so it is conducive to large-scale application and provides the possibility for large-scale manufacturing of high-efficiency solar cells. The secret of this method is that researchers have fabricated the perovskite film of this top-level solar cell at a very low temperature (50 ℃), which has low energy consumption, low cost and great application prospects. The photoelectric conversion efficiency of this laminated solar cell reaches 20.5%. EMPA researchers believe that the battery made by this method may further improve the conversion efficiency.
Molecular football is the basic material of this magic crystal
The success of this double-layer material is due to the development of surface translucent solar cells, with an efficiency of 14.2% and a penetration rate of 72%. This material is formed by depositing lead methylammonium iodide in perovskite crystals. The calcium titanium ore layer is obtained by growing on the PCBM material layer. Each PCBM molecule contains 61 carbon atoms, which are connected to each other like a football. The perovskite layer is formed by steam deposition and spin coating on this layer, so it has a football like structure, and then annealed at a "neither hot nor cold" temperature. This calcium titanium deposit can convert blue and yellow light into electrical energy. In contrast, the red and infrared parts can pass through the crystal. Therefore, researchers can design another battery under this layer of battery, which can convert this part of light into electrical energy.
Benefits of double-layer battery: better use of solar energy
EMPA researchers used CIGS (copper indium gallium selenide) batteries as the bottom layer of this laminated battery, which has been explored in the laboratory for many years. The advantage of this kind of laminated cells is that they can make full use of solar energy. Solar cells can only absorb photons whose energy is greater than the band width. If the photon energy is too low, electric energy will not be generated. If the photon energy is high, the higher part of the energy will be converted into heat and wasted. This double-layer battery can make full use of materials with different energy band widths, so it can effectively convert solar energy into electric energy.
Photoelectric conversion efficiency of more than 30% is not a dream
Although the conversion efficiency of a good single-layer polycrystalline solar cell can reach up to 25%, this kind of laminated solar cell may improve the efficiency to 30%, but there is still a lot of work to be done. Ayodhya Tiwari said, "what we are doing now is just the beginning. We need to overcome many obstacles to achieve our goal. In order to achieve this, we need interdisciplinary experience and many experiments until we find a translucent high-performance battery." Stephan B ü cheler said that the competition for solar cell efficiency is not just an academic show. "When producing solar power, only half of the cost will be reflected in the solar module itself, and the other half will be reflected in infrastructure, such as inverters, cables, carrier cells, engineering costs and installation. When the efficiency of solar cells is improved and the size is smaller, the cost of these supporting facilities is also reduced."
