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

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.