Manipulations of light-matter interactions in optoelectronics

Abstract

With the rapid development of nanofabrication techniques, plasmonic effects emerge as an indispensable tool for manipulating light-matter interactions in optoelectronics. The unique properties of plasmonic effects hold the possibility to shrink optoelectronic devices down to the nanometer scale. They can also achieve a dynamical modulation of the optical response as well as a high concentration of near-field intensity in optoelectronic devices, which are essential for developing subwavelength optics, enhancing nonlinear properties and promoting the efficiency of solar cells. In recent decades, much effort has focused on the efficient modulation of light-matter interactions. Realizing the tunable optical responses of novel nanostructures is highly desirable for designing optical waveguides and nanoantennas. The concentrated near-field intensity also holds promise for promoting the absorption of organic solar cells. Besides plasmonic effects, the magnetic dipole resonance of the low loss and high index dielectric materials also reveal possibilities to improve the absorption of organic solar cells. Here, through manipulating light-matter interactions, we aimed to propose a dynamically tunable nanoantenna, develop a theoretical tool for studying the diffraction effects of quasi-periodic structures and achieve a broadband absorption enhancement of organic solar cells. The research involved five main elements. 1. Graphene-based tunable nanoantenna

Monolayer graphene was shown to tune the optical responses of a dipole nanoantenna dynamically. Through precisely designing the nanoantenna’s geometrical parameters and the graphene dispersion, we realized the tunable nanoantenna by the mode couplings between graphene plasmon and metal plasmon. 2. Theoretical tools for studying quasi-periodic structures

We developed an advanced rigorous coupled-wave analysis method for accurately predicting the optical spectra and comprehensively understanding the diffraction effects of quasi-periodic structures. The Gaussian fluctuation and effective medium technique were adopted to capture the optical and geometrical features of quasi-periodic structures. Meanwhile, the hybridized excitations of the propagating Bloch-plasmonic and localized surface plasmon mode were also investigated by full-wave simulation. 3. Broadband absorption enhancement of organic solar cells by plasmonic asymmetric modes of gold nanostars

Through strategically incorporating gold nanostars in between hole transport layer and active layer, the excited plasmonic asymmetric modes not only favored a broadband absorption enhancement but also promoted the better-balanced transport path length for charge carriers to electrodes. 4. Optically enhanced semi-transparent organic solar cells through a hybrid metal/nanoparticle/dielectric nanostructure

A hybrid metal/nanoparticle/dielectric nanostructure was proposed to enhance the light incoupling for semi-transparent organic solar cells. The excited magnetic resonances and antireflection effects resulted in a significant promotion of both the efficiency and transparency of semi-transparent organic solar cells. 5. Predicting the efficiency limit of perovskite solar cells by an advanced drift-diffusion model through taking detailed balance theory into account

The efficiency limit of perovskite solar cells was predicted using an advanced drift-diffusion model that takes into account detailed balance theory. The radiative recombination limit at thermal equilibrium was theoretically derived through the blackbody radiation law. The proposed model can give insights to device performance optimization through evaluating efficiency degradation caused by different loss mechanisms.