Sol–Gel Route Toward Efficient and Robust Distributed Bragg Reflectors for Light Management Applications

Abstract

The optimization of functional optical devices requires the appropriate control of light propagation, which can be achieved by using engineered dielectric structures. Innovative materials combination and fabrication strategies are required to achieve a robust gain in performance without impacting manufacturing complexity and cost. In the present work, a novel liquid‐based approach is proposed for the simple and scalable fabrication of highly efficient and robust optical multilayer dielectric coatings. In particular, a sol–gel process is developed that enables the fabrication of large‐area distributed Bragg reflectors (DBR) integrating macroporous materials of controlled closed porosity. The DBRs have a very high index contrast, excellent and tunable optical properties, and high stability of performance and structural integrity with respect to crack formation and delamination, even against harsh ageing tests or solvent exposure. The potential of this approach to be integrated within existing optoelectronic architectures is demonstrated through the integration of a DBR structure as a back reflector in an amorphous silicon solar cell (a‐Si:H), resulting in a significant increase in light absorption, photocurrent, and overall efficiency. This opens the way towards simple dielectric engineering of robust photoactive devices based on the versatile use of liquid routes for the deposition of structured dielectric coatings.

Advances in Functional Solution Processed Planar 1D Photonic Crystals

“…At the lab scale, mesoporous Bragg stacks can be fabricated by sol–gel deposition methods or by direct deposition of metal oxide nanoparticles dispersion . The growth usually consists in the deposition of the nanoparticles or their precursors, and the subsequent annealing of the structure at high temperature to sinter the crystals and to provide the film with mechanical stability.…”

“…[101a] Notwithstanding such efforts, especially when polymers are used, these devices suffer from drawbacks related to low charge carriers mobility, high charge recombination rates, and limited spectral absorption, that hinder high power conversion efficiencies . In this sense, PhCs offer new strategies to improve photon collection and among these, DBRs represent the most viable approach. Recently, Martorell and co‐workers showed that DBRs made of alternated layers of MoO 3 and LiF fabricated by thermal evaporation can be implemented into bulk‐heterojunction photovoltaic cells to achieve semitransparent devices with enhanced efficiency.…”

Structural color-tunable mesoporous bragg stack layers based on graft copolymer self-assembly for high-efficiency solid-state dye-sensitized solar cells

“…The refractive index (RI) values of the OM-TiO 2 (S) layer, OM-TiO 2 (L) layer, and OM-SiO 2 (L) layer were 2.06, 1.83, and 1.27, respectively. It should be noted that only a few studies have analyzed an organized mesoporous SiO 2 layer with small wall thickness and large pore size (>50 nm) [41].…”

“…One way to overcome the drawback of using dense SiO 2 layers for TiO 2 /SiO 2 based 1D photonic crystal structures (Bragg Stack, BS) is to prepare organized mesoporous SiO 2 with tunable optical properties. Recently, the synthesis of macroporous SiO 2 layers using PMMA latex nanoparticles and the silica sol was investigated for a-Si:H solar cells [41]. And, tri-block copolymer (Pluronic P123) templated mesoporous Bragg reflectors were prepared by multiple casting of mesoporous TiO 2 and SiO 2 layers [31].…”

Hybrid Optical Fibers – An Innovative Platform for In‐Fiber Photonic Devices

“…Moreover, the combination of photonic crystals with optoelectronic devices is an important thrust of research for photodetectors and photovoltaics. [186][187][188] Future research directions in the fi eld of optoelectronic fi bers will follow this trend by integrating complex architectures to trap and absorb light effi ciently. Another direction complements this approach by looking at new materials that can interface with the presented semiconductors, to be used as electrodes or to form rectifying junctions.…”