Glass Encapsulation Research Articles

Glass-based encapsulant enabling SiC power devices to long-term operate at 300 °C

The high-temperature applications of Silicon Carbide (SiC) power devices are constrained by traditional epoxy molding compound (EMC). A significant challenge arises from the mismatch between the thermal expansion coefficients (CTE) of the encapsulant and the SiC chip, generating thermal and mechanical stresses during prolonged high-temperature operation. While glass encapsulants offer stability above 300 °C, these stresses can lead to mechanical degradation and eventual failure of SiC power devices. We design a glass-based encapsulation material to adjust the CTE of the glass to match that of the SiC chip (3–9 ppm/℃), enabling encapsulation of the device for long-term operation at 300 °C. Finite element analysis (FEA) confirms that the CTE adjustment effectively reducs internal thermal stresses. The glass composite with 10 wt% PbTiO3demonstrates a Tg of 310 °C and a CTE of 8.48 ppm/℃, successfully encapsulating a SiC schottky barrier diode in TO-247 package form. The encapsulated device exhibits low leakage current, a reverse breakdown voltage of 1,700 V, and a thermal resistance of 0.45 °C/W. Notably, the device maintains excellent performance even after 1,176 h of high-temperature aging, including 336 h at 300 °C and exhibits minimal change during thermal cycling between −50 and 150 °C for 100 cycles. Long-term performance analysis demonstrates superior stability compared to EMC encapsulation. These results highlight the potential of glass-based encapsulants for wide band gap power devices, offering reliability and performance under extreme conditions.

Highly reliable anti-reflection radiative cooling glass applicable to thermal management of solar cells

The encapsulation materials of solar cells have a significant impact on the performance and stability of the cells. Herein, an anti-reflection radiative cooling (ARRC) glass for photovoltaic (PV) devices is proposed by multi-layer design. Harnessing the synergy of anti-reflection layers and a transparent radiative cooling layer, ARRC glass can dissipate heat radiatively through molecular vibrations. Concurrently, it maintains the functionality and aesthetics of the associated devices. ARRC possesses four prominent characteristics, enabling it to serve as an encapsulation glass to enhance the performance and stability of solar cells. 1. Superior maximum visible light transmittance (0.954, 602 nm). 2. Outstanding mid-infrared emittance (0.951). 3. Excellent UV blocking performance (reached 99 % at 320 nm). 4. Marvelous thermal management performance (6.6 °C cooling for multi-crystalline silicon solar cells and 8.6 °C cooling for perovskite cells). Excellent anti-reflection and cooling performance of ARRC glass improves conversion efficiency by 1.08 % and 1.79 % for multi-crystalline silicon solar cells and perovskite solar cells (PSCs), respectively. Moreover, ARRC glass enhances the UV stability of PSCs by 4 times and significantly alleviates the thermal decomposition of PSCs. The ARRC glass, with excellent adhesion, scalability, economy, and stability, is expected to be applied on a large scale and further contribute to energy and environment sustainability.

Vacuum-Deposited Bifacial Perovskite Solar Cells.

Bifacial perovskite solar cells (Bi-PSCs) require thick perovskite layers to sufficiently absorb higher wavelength light. Also, it is critical to know which electrode (top or bottom) can more efficiently harvest the direct incident solar irradiance. Here, fully vacuum-deposited Bi-PSCs are reported with perovskite layer thicknesses ranging from ∼720 nm to 1.3 μm. With an optimized ITO top-electrode, the Bi-PSCs generated higher current density under top-illumination by >1 mA/cm2, attaining the highest value of 24.98 mA/cm2. The best Bi-PSC exhibited an efficiency of 19.6% under top-illumination and 18.71% under bottom-illumination, resulting in a high bifaciality factor of ∼0.95. Furthermore, even after employing cover glass encapsulation on the top-electrode, the Bi-PSCs still produced higher current density from top-illumination. Upon bifacial illumination using simulated 1-Sun light as the main illumination and a white LED light albedo of ∼0.21, the champion Bi-PSC demonstrated a current density value of ∼30.00 mA/cm2.

Passive communication for low power distributed sensors using MEMS optical cavities

Distributed sensing has been of great interest in recent research. Distributed sensors are in part defined by the methods they use to communicate. We demonstrate a new low power method of optical communication. Instead of communicating optically by generating new light to communicate using a light emitting diode or laser, our method uses optical interference to vary the reflectivity of a micro-electromechanical systems (MEMS) optical cavity. A thin air gap between an adjustable MEMS mirror made on a silicon on insulator die and glass encapsulation generates optical interference. By moving the mirror electrostatically, the reflected light intensity is modulated, and signals are transmitted passively. The transmitted signal is measured by observing the reflected light intensity with a photodiode. We demonstrate the use of fiber optic cables to deliver illumination and collect reflected light with modulated intensity. We propose that these devices may also be used in series arrays where reflected light from one optical cavity can be used as illumination for another.

Effectiveness of poly(methyl methacrylate) spray encapsulation for perovskite solar cells

For commercial applications, Perovskite Solar Cells (PSCs) need to be well encapsulated to improve long term stability. The most common method, glass-glass encapsulation, uses edge sealant materials to encapsulate the device between sheets of glass. Glass-Glass encapsulation, while providing provide adequate protection from the ambient environment, limits the use of flexible substrates for thin film solar cells due to its rigidity. Additionally, the added weight of glass encapsulation reduces the specific power (W kg−1) of PSCs, which is an important factor when designing solar cells for aerospace applications. Here we demonstrate that commercially available acrylic spray encapsulation offers efficient and robust stability for PSCs. It is shown that applying the encapsulation via this method does not degrade the PSCs, unlike other literature and glass-glass encapsulation methods. Additionaly, it is shown that 1 coat of acrylic spray encapsulation has an effective thickness of ∼1.77 µm and a weight of ∼6 mg. For stability measurements, PSCs with an acrylic coating show a 4% increase in performance after ∼730 h under dark storage conditions and retain 88% of their initial power conversion efficiency after 288 h under 85% relative humidity 25 °C. We anticipate our assay to be a starting point for further studies into spray encapsulation materials and methods not just for terrestial applications, but for aerospace applications as well.

Comparison of Glass–Glass versus Glass–Backsheet Encapsulation Applied to Carbon-Based Perovskite Solar Cells

The record photovoltaic performance of perovskite solar cells is constantly increasing, reaching 26% currently. However, there is a crucial need for the development of simple architectures that are compatible with large-scale industrialization and possess adequate stability. The aim of the work presented here is to compare the efficiency of glass–glass and glass–backsheet encapsulations for carbon-based perovskite solar cell application, which possesses a great potential for industrialization. This was conducted by first separating the relative effects of humidity and heat. A time evolution of the macroscopic power conversion efficiency (PCE) was performed, together with specific characterizations in order to scout the origin of flaws and degradations. A significant contribution of the paper is the identification of both TiO2 and carbon layers as barriers against moisture permeation, which inhibit moisture paths through the interfaces. This is the origin of the equivalent durability of both studied systems, even if the glass–backsheet encapsulation was found to be less efficient than the glass–glass encapsulation at protecting perovskite from damp-heat aging when TiO2 or carbon layers are not used.

Restoring adsorption properties of graphene sensor with printable glass encapsulation using UV illumination

Graphene is a 2D material that has been widely researched for its potential as a gas-sensing material, but its environment-sensitive electronic properties have limited its use in practical applications. In this work, a graphene chemi-resistive sensor is first integrated with a 3D-printed fused silica chamber with an internal volume of 50 µl. The adsorption properties of graphene film are then regenerated using ultraviolet illumination. We have shown in this work that sensor response towards the target acetone sample can be regained successfully after more than 2 months of operation using UV illumination. The sensor's response at room temperature towards direct on-chip injection of acetone vapor ranging from 5 ppm to 1,000 ppm was studied and the data was linearly fitted. The wide dynamic response of the graphene sensor was used to demonstrate its usability for practical soil testing applications. We successfully detected 11 ppm, 20 ppm and ∼605 ppm of acetone vapor in artificially spiked soil samples. In conclusion, our new on-chip integrated gas chamber is extremely robust, provides repeatable results after long-term operation, and offers a direct route for on-chip sample injection.

Fully glass frit encapsulated dye-sensitized solar cells: Challenges for hermetical sealing of electrolyte injection holes

Dye-sensitized solar cells (DSSC) are the fastest-evolving indoor PV technology for long-term wireless power for the internet of things (IoT) devices and wireless sensors. Hermetic encapsulation is crucial for the reliable decoupling of extrinsic and intrinsic degradation factors of DSSCs as well as to protect long-lasting devices against moisture, oxygen ingress, and electrolyte leakage. Encapsulating the edges with glass frits has proven the most durable method of overcoming the device's hermeticity challenge. However, sealing the electrolyte injection holes with glass remained an elusive objective achieved in this study by structuring the glass into a capillary shape and laser-induced fusing the capillary edge. The structured injection hole effectively dissipates heat and thermal stress; when the glass sealing temperature reaches around 1200 °C, the device's cavity does not exceed 50 °C. The method produces sealed devices that passed theMIL-STD-883 helium leakage and the IEC 61646 humidity-freeze tests. After 4336 h of accelerated aging according to ISOS-L-2/3 protocols, entirely glass-sealed DSSCs maintained their photocurrent conversion efficiency (PCE) while conventionally polymer-sealed and partially glass-sealed counterparts exhibit inverse PCE progression, with an average deterioration rate 1.8·10−3 and 2.2·10−3 per day, respectively. Full glass encapsulation allows long-life DSSCs and durable long-term stability certification. Extrinsic degradation is prevented and opens a trustworthy assessment of possible intrinsic degradation factors.

Light‐Driven Polymer‐Based All‐Solid‐State Lithium‐Sulfur Battery Operating at Room Temperature

AbstractPoly(ethylene oxide)‐based polymer all‐solid‐state LiS battery is a promising candidate due to its high specific energy, good processability, and low cost. However, the poor room temperature ionic conductivity limits its further development. Here an innovative photothermal battery technology is proposed to realize the normal operation at room temperature. This design places the 3D Cu substrate with Cu/Si core‐shell structures between Li anode and outer encapsulation glass, so that the light can come in and generate heat efficiently by utilizing the carrier nonradiative recombination of Si nano shell, then the heat quickly transfers to the battery system through Cu core. Once simulated sunlight irradiates, the battery achieves a fast reaction kinetics and superior photothermal conversion, thus realizing a lifespan of over 20 cycles with a capacity of 1089.9 mAh g−1 at 0.2 C. Even on the actual sunlight irradiation, a high discharge/charge capacity of 1065.2/1036.5 mAh g−1 is also reached, indicating an excellent reversible electrochemical process. Moreover, the 3D nanostructure can accommodate the fatal volume variation of lithium and reduce the effective current density, thus suppressing the dendrite nucleation and growth. This study will open the avenue to develop a room temperature polymer all‐solid‐state LiS battery using photothermal technology.

Evaluation of encapsulation strategies for solution-processed flexible organic light-emitting diodes

Owing to the sensitivity of organic materials to ambient conditions, encapsulation of organic light-emitting diodes (OLEDs) is critical. In this work, Al2O3 film, deposited by atomic layer deposition (ALD) technique, on flexible polyethylene terephthalate (PET) substrate is used as a barrier film. Al2O3 is also deposited directly on OLED as thin-film encapsulation. Electrical Ca tests are used to measure water vapor transfer rate (WVTR) values, and an optimum WVTR value of 9 *10−4 g/m2/day using 43 nm Al2O3 film has been obtained. The related results on five different encapsulation structures for solution-processed OLEDs: (i) glass to glass encapsulation (G2G) as a reference, (ii) glass to barrier film encapsulation (G2B), (iii) glass to direct thin-film encapsulation (G2D), (iv) barrier to barrier film encapsulation (B2B), and (v) barrier to direct thin-film encapsulation (B2D), are evaluated. The operating half-lifetime values of OLEDs with G2B- and G2D-encapsulation are 54% and 82% of the half-lifetime with G2G encapsulation, respectively. The lifetime of flexible OLED devices with B2D encapsulation is also 34% more than that with B2B encapsulation. Based on the bending stress analysis, the estimated critical bending radius for B2B and B2D encapsulation of flexible OLEDs are 16.83 and 7.07 mm, respectively.

Glass encapsulation of molecular-doped epitaxial graphene for quantum resistance metrology

The large Landau energy spacing, stemming from the linear energy-momentum dispersion of quasi-particles in graphene, allows an efficient realization of the quantum Hall effect at a small density of charge carriers. Promising scalable epitaxial graphene on silicon carbide (SiC), however, requires molecular doping, which is generally unstable under ambient conditions, to compensate for electron transfer from the SiC substrate. Here, we employed classical glass encapsulation common in organic electronics to passivate molecular-doped epitaxial graphene against water and oxygen molecules in air. We have investigated the stability of Hall quantization in a glass-encapsulated device for almost 1 year. The Hall quantization is maintained above a threshold magnetic field within 2 nΩ Ω−1 smaller than the measurement uncertainty of 3.5 nΩ Ω−1 through multiple thermal cycles for almost 1 year, while the ordinary unencapsulated device in air distinctly shows a relative deviation larger than 0.05% from the nominal quantized Hall resistance in 1 month.

Reversible Phase Segregation and Amorphization of Mixed-Halide Perovskite Nanocrystals in Glass Matrices.

Mixed-halide perovskites have attracted great attention in applications of lighting and photovoltaic devices due to their excellent properties. Understanding the phase segregation mechanism of mixed-halide perovskite has significance for suppressing the performance degradation of optoelectronic devices. Herein, we investigate the mixed-halide perovskite nanocrystals (NCs) in isolation from the external factors (oxygen, moisture, and pressure) using glass encapsulation, which shows excellent photostability against phase segregation. By monitoring the structural evolution of the NCs in glass matrices, the coexisting phase segregation and amorphization of mixed-halide perovskites are observed in real-time. The results show that thermal-induced local temperature increase plays a dominant role in the phase segregation of mixed-halide perovskite NCs. The recovery process is driven by the spontaneous crystallization of the amorphous mixed-halide phase. The clarified dynamic equilibrium process between the compositional segregation (mixing) and structural disorder (order) gives us a better insight into the reversible phase segregation mechanism of mixed-halide perovskite.

P‐40: Techniques of Touch Sensing and Display Driving for Avoiding Display Artifacts for Flexible OLED Applications

Currently, use of flexible OLED (Organic Light Emitting Diode) displays is increasing, especially in mobile phone applications due to the high flexibility in industrial design they provide for curved edge and foldable smartphones and tablets. For flexible OLED, TFE (Thin Film Encapsulation) technology is widely used to prevent water and oxygen permeation, and as the name suggests, it is extremely thin. Accordingly, when on‐cell touch panels transition from rigid OLED with ~200 um glass encapsulation to flexible OLED with ~8 um TFE, the distance between display electrodes and the touch sensor becomes considerably closer. The dramatically increased capacitive coupling between the display and touch systems produces a correspondingly increased risk of errors in voltages driven to the display pixels due to touch sensing modulation coupling into the display system, resulting in deteriorated display image quality. In this paper, we introduce touch sensing and display driving techniques for avoiding display artifacts for flexible OLED applications.

Stable Cobalt-Mediated Monolithic Dye-Sensitized Solar Cells by Full Glass Encapsulation.

Dye-sensitized solar cells (DSSCs) emerged in the market as one of the most promising indoor photovoltaic technologies to address the need for wireless powering of low-consuming electronics and sensor nodes of the internet of things (IoT). The monolithic design structure of the cell (M-DSSCs) makes the devices simpler and cheaper, and it is straightforward for constructing in-series modules. The most efficient DSSCs reported so far are Co(III/II)-mediated liquid junction cells with acetonitrile electrolytes; however, they are mostly unstable. This study reports on highly stable cobalt-mediated M-DSSCs, passing thermal cycling tests up to 85 °C according to ISOS standard protocols. Under 1000 h of aging in the dark and under simulated solar and artificial light soaking, all tested cells improved or retained their initial power conversion efficiency. Advanced long-term stability was achieved by eliminating the extrinsic factors of degradation, such as the interaction of the cell components with the environment and electrolyte leakage. This was obtained by encapsulation of the devices using a glass-frit sealant, including the holes for filling up the liquid components of the cells. The hermeticity of the encapsulation complies with the MIL-STD-883 standard fine helium gas leakage test, and its hermeticity remained unchanged after humidity-freeze cycles according to IEC 61646. The elimination of extrinsic degradation factors allowed reliable assessment of inner factors accountable for aging. The impact of the ISOS-protocol test conditions on the intrinsic device stability and long-term photovoltaic history of the M-DSSCs is discussed.

Hybrid Passivated Red Organic LEDs with Prolonged Operation and Storage Lifetime

In addition to mobile and TV displays, there is a trend of organic LEDs being applied in niche markets, such as microdisplays, automobile taillights, and photobiomodulation therapy. These applications mostly do not require to be flexible in form but need to have long operation lifetimes and storage lifespans. Using traditional glass encapsulation may not be able to fulfill the rigorous product specification, and a hybrid encapsulation method by combining glass and thin-film encapsulation will be the solution. Conventional thin-film encapsulation technology generally involves organic and inorganic multilayer films that are thick and have considerable stress. As a result, when subjected to extreme heat and stress, the film easily peels off. Herein, the water vapor transmission rate (WVTR) of a 2 µm silicon nitride film prepared at 85 °C is less than 5 × 10−5 g/m2/day and its stress is optimized to be 23 MPa. Red organic LEDs are passivated with the hybrid encapsulation, and the T95 lifetime reaches nearly 10 years if the LED is continuously driven at an initial luminance of 1000 cd/m2. In addition, a storage lifespan of over 17 years is achieved.

CdSe and CsPbBr3 quantum dot Co-doped monolithic glasses as tunable wavelength convertors

CdSe and CsPbBr3 quantum dots (QDs) are well studied photoluminescent materials due to their extraordinary emission properties. However, their vulnerability against environmental conditions limits their integration into further applications. At this point, glass encapsulation offers promising durability features due to its robust and dense structure. In this study, CdSe and CsPbBr3 QDs are successfully synthesized in the same glass host through the melt-quenching technique followed by a single heat-treatment process. Excitation wavelength dependent photoluminescence properties are investigated and emission color tunability of monolithic glasses from yellow-green to red is demonstrated. Favorable quantum yield values are obtained as 21.78% and 16.63% under 345 and 365 nm excitation wavelengths, respectively. The prepared glasses demonstrate high potential to be used as tunable wavelength convertors for state-of-the-art photonic and opto-electronic applications.

Organic Light‐Emitting Transistors in a Smart‐Integrated System for Plasmonic‐Based Sensing

AbstractThe smart integration of multiple devices in a single functional unit is boosting the advent of compact optical sensors for on‐site analysis. Nevertheless, the development of miniaturized and cost‐effective plasmonic sensors is hampered by the strict angular constraints of the detection scheme, which are fulfilled through bulky optical components. Here, an ultracompact system for plasmonic‐sensing is demonstrated by the smart integration of an organic light‐emitting transistor (OLET), an organic photodiode (OPD), and a nanostructured plasmonic grating (NPG). The potential of OLETs, as planar multielectrode devices with inherent micrometer‐wide emission areas, offers the pioneer incorporation of an OPD onto the source electrode to obtain a monolithic photonic module endowed with light‐emitting and light‐detection characteristics at unprecedented lateral proximity of them. This approach enables the exploitation of the angle‐dependent sensing of the NPG in a miniaturized system based on low‐cost components, in which a reflective detection is enabled by the elegant fabrication of the NPG onto the encapsulation glass of the photonic module. The most effective layout of integration is unraveled by an advanced simulation tool, which allows obtaining an optics‐less plasmonic system able to perform a quantitative detection up to 10−2 RIU at a sensor size as low as 0.1 cm3.

A Review on Emerging Barrier Materials and Encapsulation Strategies for Flexible Perovskite and Organic Photovoltaics

AbstractPerovskite solar cells (PSCs) and organic photovoltaics (OPVs) have undergone rapid development within the last decade, exhibiting exciting properties such as high efficiency, flexibility, and the potential for large‐scale fabrication through roll‐to‐roll (R2R) processing. Despite this, operational stability is recognized to be an ongoing challenge as prolonged device lifetimes are scarcely observed. This instability can be narrowed down to both “intrinsic degradation” and “extrinsic degradation,” with exposure to moisture and oxygen having detrimental effects on device performance. A means of delaying the degradation of flexible PSC and OPV devices is through barrier encapsulation. Despite glass encapsulation exhibiting ideal barrier properties, the potential for flexible devices and high‐throughput R2R fabrication requires the development of flexible barrier materials and encapsulation strategies. These barriers must demonstrate outstanding moisture permeation resistance, high transparency, chemical and thermal stability, and must be able to withstand repeated mechanical deformation. Herein, the fundamental principles of PSC and OPV devices are initially discussed, highlighting the degradation mechanisms and current stability obstacles. A review of the latest flexible barrier materials and encapsulation strategies follows, introducing stability studies that have been undertaken on flexible PSCs and OPV, along with suggestions as to the direction that future research may take.

Evaluation of heavy metal leaching under simulated disposal conditions and formulation of strategies for handling solar panel waste.

With the steady growth in the worldwide solar installed capacity, there is an immediate concern about the fate of the solar panels at the end of their life. Solar panel waste is often disposed of indiscriminately, exposing the environment to chemical hazards. The major objective of the current study was to evaluate the leaching potential of the polycrystalline solar panel waste under different simulated disposal conditions through toxicity characteristic leaching procedure (TCLP), synthetic precipitation leaching procedure (SPLP) and pH static leaching procedure tests. Moreover, the study evaluates the effects of ageing and the breakage of the Glass Laminate Encapsulation (GLE) of solar panels on their leaching potential. Among the metals studied (silver (Ag), aluminium (Al), cadmium (Cd), chromium (Cr), copper (Cu), manganese (Mn), lead (Pb), and zinc (Zn)), the concentrations of Pb were as high as 9.3mg/L, 1.4mg/L, 6.7mg/L in the TCLP, SPLP, and pH static test respectively. This indicated the hazardous nature of the waste with leaching potential of Pb above the permissible limits stipulated by various regulatory bodies. The presence of GLE reduced the mobility of Pb by a factor of 4.1-8.8 in the TCLP test, thereby rendering the waste as non-hazardous for its disposal in a landfill. However, the indiscriminate disposal of solar panel waste in the natural environment as simulated by the SPLP test indicated its harmful nature irrespective of the physical condition. Ageing of the solar panels before disposal and acidic pH conditions also positively influenced the leaching potential of the selected metals subjected to their reactivity and the accessibility of internal layers of waste to the leaching solution. Strategies such as extended producer responsibilty, advance-recycling fee, and incentivizing the recycling industry will lead to both economic benefit creation and effective waste management of this waste stream.

A comparative performance evaluation and sensitivity analysis of a photovoltaic-thermal system with radiative cooling

Radiative cooling (RC) of solar cells has received growing attention in recent years primarily due to its passive nature as compared to the other active cooling techniques. By using novel high emittance materials, the RC technique can also be integrated with a photovoltaic-thermal (PVT) system, to eventually improve the system's total efficiency (electrical and thermal output) during the day and provide additional cooling power at night. To quantify the effect of enhanced RC in a PVT system, this study investigated the performance of a regular glass encapsulated PVT module, and a spectrally modified module by using a polydimethylsiloxane coating on top of the glass layer to simulate enhanced RC. An experimentally validated simulation model was developed for performance comparison. Furthermore, a sensitivity analysis was conducted to investigate the influence of varying input parameters on system output performance. Results show that during the day, solar cell operating temperature reduced by most 1.7 °C, and electrical efficiency and total exergy efficiency increased by 0.76% and 0.5%, respectively. As for nighttime, an additional 4–7 W/m2 cooling power can be obtained. Although some improvements, the potential gains achieved by integrating enhanced RC in PVT systems are not substantially large as compared to the regular glass encapsulation in commercial PVT modules, since glass naturally has a fairly high emittance in the atmospheric window.