This PDF file contains the front matter associated with SPIE Proceedings Volume 12668, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

The realization of a net-zero energy built environment is challenging, especially in dense city centers with highrise buildings. While in suburban residential areas, roof space in combination with efficient solar photovoltaics (PV) can lead to energy self-sufficiency, for high-rise buildings this is only potentially possible if all fa¸cades are also harvesting solar energy. For aesthetic and occupational health reasons, PV fa¸cades should be (partly) transparent and color-neutral. Solar energy harvesting windows based on luminescent solar concentrators are one class of transparent PV that combines transparent waveguides concentrating light on their sides where solar cells are mounted. A compromise between color-neutral transparency and harvesting efficiency must be found, leading to average visible transparency values of >70%, color rendering index >80, and efficiencies of 2-3%. A range of luminescent species embedded in the waveguide has been investigated, from organic dyes to nanoparticles based on chalcogenides and perovskites, while combinations of those are investigated as tandem structures. This contribution will review recent experimental and simulation results, and will derive promising strategies to approach a theoretical limit of 20% color-neutral transparent efficient luminescent solar concentrators, which is based on full utilization of the UV/blue and the red/IR part of the solar spectrum, with limited utilization of the visible part.

Transformative solar technologies with high efficiencies and low costs are required to increase the deployment of solar cells. Luminescent solar concentrators (LSCs) have the potential to enable these designs but have not achieved significant efficiencies. First, we will explore a generalized model to elucidate the necessary light trapping requirements for high concentration LSCs. Because the light trapping necessary will require nanophotonic elements, we will explore a design which uses CdSe/CdS quantum dots embedded in a 1-D photonic crystal (SiO₂ and Si₃N₄). Angular emission measurements of a prototype show a significant decrease in the escape loss and reduced reabsorption losses.

Transition metal di-chalcogenides (TMDCs) have strong potential for ultra -thin electronic and photonic applications because of their range of electronic and optical properties, 2D layered structure, and tunability of properties by dopants and hybrid alloys. TMDCs have high atomic masses compared to commonly used semiconductors, which makes them resistant to damage by high energy particles in space. We have studied the fundamental electronic and optical properties of various tungsten-based TMDCs by Density Functional Theory (DFT) calculations. We then developed a solar cell model composed of heavier TMDCs with photon management features to design high-performing photovoltaic devices which are ultra-thin, lightweight, with significantly enhanced resistance to radiation-induced damage. Here, we model electro-optic properties and photovoltaic performance of various combinations of tungsten-based TMDCs containing sulfur, selenium and tellurium. Device simulations conducted using the AM0 space solar spectrum yield high efficiencies above 17% for the tungsten-based devices. The non-ionizing energy loss (NIEL) due to high energy protons for tungsten-based TMDCs are much lower than common photovoltaic semiconductors, such as silicon, resulting in significantly reduced displacement damage doses (DDD) from space radiation. Our results show that TMDCs have great potential for implementation in radiation-resistant electronic and photonic technologies in the space environment.

We study the relation between angular spectral absorptivity and emissivity for any thermal emitter, which consists of any linear media that can be dispersive, inhomogeneous, bianisotropic, or nonreciprocal. First, we establish an adjoint Kirchhoff’s law for mutually adjoint emitters. This law is based on generalized reciprocity and is a natural generalization of conventional Kirchhoff’s law for reciprocal emitters. Using this law, we derive all the relations between absorptivity and emissivity for an arbitrary thermal emitter. We reveal that such relations are determined by the symmetries of the system, which are characterized by a Shubnikov point group. We classify all thermal emitters based on their symmetries using the known list of all three-dimensional Shubnikov point groups. Each class possesses its own set of laws that relates the absorptivity and emissivity. We numerically verify our theory for all three types of Shubnikov point groups: Grey groups, colorless groups, and black/white groups. We also verify the theory for both planar and non-planar structures with single or multiple diffraction channels. Our theory provides a theoretical foundation for further exploration of thermal radiation in general media.

Due to the increasing demand for using compact and low-power wireless sensors, the interest in designing hybrid cells with the dual properties of energy harvesting and storage has been growing in recent years. Among different designs, twoelectrode hybrid cells are more suitable for low-voltage and low-power electronics. Using a redox-active polyvinyl alcohol (PVA)/polyaniline (PANI)-based gel electrolyte, a two-terminal device was fabricated and tested in this study. The performance of the gel electrolyte was assessed in different devices made from a carbon nanotube-based cathode and four different anodes. All the tested anodes were made from a conductive glass coated with mesoporous TiO₂, transparent TiO₂, opaque TiO₂, or mesoporous ZrO2. Cyclic voltammetry (CV), open circuit voltage (OCV), and short circuit current (SCC) were conducted to investigate the properties of the devices. The fabricated device with the transparent TiO₂ coating has shown a capacitance of 0.363 mF and with the opaque TiO2 coating has shown a photovoltaic potential of 244 mV. The results suggest further studies on materials nanostructure to achieve higher energy conversion efficiency and larger storage capacitances for future applications in wireless devices.

Non-toxic, low cost, and environment-friendly solar absorber materials is a great subject of interest for research community for photovoltaic applications. The preparation of these solar cell materials by adopting a greener synthesis route still remains a challenge. Herein we present a surfactant free, cheaper, non-toxic and highly scalable one pot hydrothermal synthesis of Cu2ZnSnS4 (CZTS) ink for its efficacy in photovoltaic application. The properties of CZTS ink were analyzed by utilizing Photoluminescence (PL), Fourier Transform Infrared (FTIR) spectroscopy, Scanning Electron Microscopy (SEM), and X-ray diffraction (XRD) characterization techniques. The highly pure kesterite structure of CZTS was confirmed by the diffraction peaks observed using XRD. The calculated lattice parameters and from the XRD data are 0.54 nm and 1.09 nm respectively having a full width half maxima (FWHM) of 0.81 corresponding to the highly intense diffraction peak (112). The recorded PL spectra having intense PL main peak at 823 nm confirms the highly luminescent behavior of our synthesized CZTS ink. The formation of a very good surface morphology has been confirmed by SEM image. The observed FTIR peaks at 1456 cm ^-1 and 712 cm ^-1 govern the existence of functional groups C-H and C-C bending vibration respectively. This interesting study shows the ability to synthesize surfactant free, low cost and high performance CZTS ink for its utility in photovoltaic domain.