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Method for manufacturing solid-state devices by fabricating the essential components as freestanding layers, then assembling as needed.
About
Every solar cell technology is founded on monolithic fabrication in which devices are made by sequentially depositing layers of materials on top of each other. However, monolithic fabrication contributes to two major barriers facing solar cells: i) high manufacturing and recycling costs, and ii) process incompatibility between films of different material class. Additionally, this rigid matrix renders the entire cell susceptible to defects that may result in poor performance or complete failure of the cell. This new technology allows solid-state devices to be assembled and disassembled at will with freestanding layers creating a modular device. The University of Hawaii (UH) has developed a new method for manufacturing solid-state devices, such as solar cells, diodes or capacitors, by fabricating the essential components (i.e. contacts, absorber, emitter) individually as freestanding layers then assembling as needed. This unique approach involves first dispersing particles with the appropriate material properties (e.g., semiconducting, insulating or metallic) into a non-conductive transparent polymer matrix. Next, the particle/polymer is formed, cured and then liberated to create the freestanding layers. Made in this way, sufficient particle surface area is exposed by protruding from the hardened polymer to allow for particle-particle coupling to occur between adjacent layers. The freestanding layers are then stacked to create a modular solid-state device which features an architecture that can be combined, exchanged, and replaced at will. UH has fabricated freestanding contact layers using 50 micron silver particles embedded in a hardened epoxy as proof-of-concept. These freestanding contacts possess both high optical transmittance and out-of-plane conductivity (R=0.27 ohm-cm2, outperforming commercial FTO substrates. Furthermore, UH has demonstrated the coupling of two contact layers yielding an out-of-plane series resistance of 2.0 ohm-cm2. These modular devices overcome the major barriers encountered by monolithic fabrication. Since modular devices do not rely on monolithic fabrication, they do not require resource-intensive vacuum equipment and thus will drive down fabrication costs by reducing capital and operating expenditures. Recycling costs and e-waste will be reduced as each freestanding layer can be dissolved in an organic solvent, thereby liberating the particles to be collected for future use. All layers of the solid-state device are fabricated independently; therefore, underlying layers are not required to withstand the subsequent depositions of a monolithic fabrication process and eliminating unintentional interfacial reactions.
Key Benefits
UH’s disruptive new technology has great potentials in advancing solid-state solar devices where monolithic fabrication suffers from process incompatibilities, unintentional interfacial reactions, and high manufacturing and recycling costs. From a practical standpoint, a modular solid-state device will be offered with multiple free standing layers (FSL). In photovoltaics applications, one may choose to use one FSL comprising specific semi-conducting particles over another to achieve a desired voltage or current output. If higher efficiency is required, a second FSL with complementary semi-conducting particles can be stacked. For energy storage, a FSL comprising either HfO2, SiO2 or SrTiO3 particles could be sandwiched between two FSL electrodes to achieve a desired capacity value. In electronics, 3 FSLs made of p-type or n-type semiconductor particles can be stacked to form the emitter, the base and the collector of a tunable bipolar transistor. Flexible Free standing Lightweight Modular Room temperature processing Tunable optoelectronics
Applications
Solid state device manufacturing Photovoltaics Energy storage