Abstract
A 900 nm thick TiO2 simple cubic photonic crystal with lattice constant 450 nm was fabricated and used to experimentally validate a newly-discovered mechanism for extreme light-bending. Absorption enhancement was observed extending 1–2 orders of magnitude over that of a reference TiO2 film. Several enhancement peaks in the region from 600–950 nm were identified, which far exceed both the ergodic fundamental limit and the limit based on surface-gratings, with some peaks exceeding 100 times enhancement. These results are attributed to radically sharp refraction where the optical path length approaches infinity due to the Poynting vector lying nearly parallel to the photonic crystal interface. The observed phenomena follow directly from the simple cubic symmetry of the photonic crystal, and can be achieved by integrating the light-trapping architecture into the absorbing volume. These results are not dependent on the material used, and can be applied to any future light trapping applications such as phosphor-converted white light generation, water-splitting, or thin-film solar cells, where increased response in areas of weak absorption is desired.
Highlights
In several areas of photonics and optoelectronics, the efficient absorption and conversion of light into useful energy is of paramount importance
We identify a precise mechanism for path length enhancement, which has its origin in the refraction of light by a three-dimensional photonic crystal[27, 28] (PC)
parallel-to-interface refraction (PIR) ideally provides photons with an effectively infinite path length through the PC, a result that manifests as a spike in the absorption spectrum at the resonant frequency where the necessary boundary conditions are satisfied
Summary
In several areas of photonics and optoelectronics, the efficient absorption and conversion of light into useful energy is of paramount importance. The performance of materials otherwise suitable for economical large-scale production is limited by different factors, such as imperfect near-infrared absorption (crystalline silicon[1] and ruthenium-based dyes2, 3), or charge diffusion length (amorphous silicon[4]) To circumvent these limitations while addressing cost and material consumption[5,6,7], charge transport[8] and other efficiency concerns[9, 10], it is beneficial to engineer structures that can extend the photon’s optical path length by altering how light flows through these devices. The experimental validation of PIR provides an opportunity to use simple cubic PCs as an ordered, three-dimensional network that refracts light according to the dispersion relation This approach to absorption enhancement is amenable to infiltration by various agents, such as dyes, polymers, and nanophosphors, and is suitable for investigating PC-induced light emission enhancement. We anticipate that the scope of these results will extend beyond thin-film solar cells to other applications, like phosphor conversion in light-emitting diodes[30], and water-splitting[20]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
