Private: Nagel and Scarpulla Top Downloaded Article of Optics InfoBase
An article writen by James R. Nagel and Michael A. Scarpulla, “Enhanced absorption in optically thin solar cells by scattering from embedded dielectric nanoparticles.” is one of the top downloaded articles in energy from Optics Express.
The paper itself is a study of light trapping in thin films. Using numerical simulations, we explored what would happen if little spheres of silicon dioxide (SiO2) were placed inside a chunk of silicon. Ordinarily, if light passes through a flat slab of material, it gets exponentially attenuated in proportion with the total thickness. However, if the light can be scattered around (say, by bouncing off of obstacles along the way), then the rays of light are effectively traveling a greater distance in the material, and therefore get absorbed more. This has applications in thin-film solar cells, wherein the total thickness of bulk stuff is limited. So by scattering light around inside the solar cell, more light is “trapped” inside and produces a more efficient device.
Abstract: We present a concept for improving the efficiency of thin-film solar cells via scattering from dielectric particles. The particles are embedded directly within the semiconductor absorber material with sizes on the order of one wavelength. Importantly, this geometry is fully compatible with the use of an anti-reflective coating (ARC) to maximize light capture. The concept is demonstrated through finite-difference time domain (FDTD) simulations of spherical SiO2 particles embedded within a 1.0 µm layer of crystalline silicon (c-Si) utilizing a 75 nm ARC of Si3N4. Several geometries are presented, with gains in absorbed photon flux occurring in the red end of the spectrum where silicon absorption is weak. The total integrated absorption of incident photon flux across the visible AM-1.5 spectrum is on the order of 5-10% greater than the same geometry without any dielectric scatterers.
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