Hydrogen technologies: Optical properties of hydrogenated amorphous thin films for solar cells

Summary: Hydrogen technologies are rapidly penetrating all aspects of life, forming the basis of the Hydrogen Civilization of the future. Hydrogenated amorphous silicon (a-Si:H) thin films are widely used in solar cells due to their advantageous optical properties. Here are some key points about their optical characteristics: 1. Optical Band Gap: The optical band gap of a-Si:H can be tuned by adjusting the hydrogen content during deposition. This allows for better absorption of sunlight and improved efficiency in solar cells. 2. Refractive Index: The refractive index of these films is crucial for designing anti-reflective coatings, which enhance the amount of light entering the solar cell. 3. Urbach Energy: This parameter indicates the width of the tail of localized states in the band gap. Lower Urbach energy values are desirable as they signify fewer defects and better electronic properties. 4. Absorption Coefficient: High absorption coefficients in the visible spectrum are essential for thinfilm solar cells to absorb maximum sunlight with minimal material. 5. Hydrogen’s Role: Hydrogenation helps in passivating dangling bonds in the silicon network, reducing defects and improving the material’s optical and electronic properties. These properties make hydrogenated amorphous silicon thin films a popular choice for cost-effective and efficient solar cells. Infrared (IR) absorption spectra are investigated hydrogenated amorphous solid solution films a-Si1-xGex: H (x = 0 ÷ 1) plasma chemical vapor deposition at different partial pressures of hydrogen PH2. Defined force, oscillator, which essentially depended on PH2. It is shown that the hydrogen contained in films mostly in the forms of GeH, SiH. Using integrated acquisitions JW, determined the amount of hydrogen in the films. Film properties depend on the composition and level of hydrogenation. The number of hydrogen atoms in films, varied by changing the composition of the gas mixture. In the work measured IR absorption for films a-Si1-xGex: H, a-Ge:H and a-Si0,88Ge0, 12: H based on films and a-Si: H and a-Si0,88Ge0, 12: H fabricated three-layer solar cells with an area of item 1.3 cm2 and efficiency equal to ~9.5%.