Broadband Coherent Absorption in Chirped-Planar-Dielectric Cavities for 2D-Material-Based Photovoltaics and Photodetectors

Abstract

Atomically thin materials such as graphene and transition metal dichalcogenides are being developed for a range of optoelectronic devices, but their applications are currently limited by low light absorption. Here, we describe a dielectric cavity design with chirped Bragg reflectors for broadband coherent absorption. The chirped cavity absorption is calculated by the transfer matrix method and optimized using the Nelder–Mead optimization protocol. We numerically demonstrate that with cavity enhancement, a monolayer MoS2 photodetector absorbs as much as 33% of incident visible light over a 300 nm bandwidth, and the external quantum efficiency of an atomically thin monolayer graphene/monolayer MoS2 solar cell can be enhanced 3.6 times to a predicted value of 7.09%. The proposed layered dielectric structures operate across a wide range of incident angles and could enable applications for atomically thin photodetectors or solar cells.