Abstract
Efficient optical energy transfer is key to many technologies, ranging from biosensing to photovoltaics. Here, for the first time we show that by introducing a random medium with appropriate filling factor, absorption in a specific volume can be maximized. Using both numerical simulations and an analytical diffusion model, we identify design rules to maximize absorption in the system with different geometrical and scattering properties. By combining a random medium with an open photonic cavity, we numerically demonstrate a 23-fold enhancement of the absorbed energy. We also show how absorption as high as 99% can be reached in a device as thin as 500 μm for normal incidence illumination. Finally, our data indicate that introducing a non-absorbing random medium into a light trapping system for thin solar cells can enhance absorption of energy by a factor of 2.2. This absorption enhancement, caused by the random medium, is broadband and wide-angle and can help design efficient solar cells, light trapping devices, biosensors and random lasers.
Highlights
Light propagation in disordered optical materials has been extensively studied for Anderson localization [1,2,3], random lasers [4,5,6,7] and light focusing below the diffraction limit [8, 9]
We theoretically demonstrate that random media can improve the absorption of light in existing light trapping systems by 2.2, demonstrating that the maximal absorption regime in random media is promising for light harvesting devices
To explain the maximal absorption regime in random media, we first introduce the known behavior for light reflection and transmission in random media [63]
Summary
Light propagation in disordered optical materials has been extensively studied for Anderson localization [1,2,3], random lasers [4,5,6,7] and light focusing below the diffraction limit [8, 9]. Elongated optical paths – present in random media – recently paved the way for new sensing applications: gas camera sensors [13], multiscattering-enhanced absorption spectroscopy [14] and multiscattering-enhanced optical probes [15,16,17]. Random media offer the possibility to improve photovoltaic devices by enhancing their absorption and increasing the optical path of light [18,19,20]. Recent trends in photovoltaics suggest moving towards thin film solar cells, where the recombination losses of generated hole-electron pairs are minimized [21]. Such trend requires efficient light trapping methods to maximize absorption within a thin solar cell [22]. Geometric engineering schemes and gratings can suffer from defects and often require alignment or a tracking system, whereas
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