Triple Cross-Linking Engineering Strategies for Efficient and Stable Inverted Flexible Perovskite Solar Cells.

Inverted flexible perovskite solar cells (fPSCs) are promising for commercialization due to their low cost, lightweight, and excellent stability. However, enhancing fPSCs' power conversion efficiency and stability remains challenging. Here, an unprecedented triple cross-linking engineering strategy is innovatively exhibit for efficient and stable inverted fPSCs. First, a carefully designed cross-linker, 4-fluorophenyl 5-(1,2-dithiolan-3-yl) pentanoate (FB-TA), is added to the perovskite precursor solution. During the perovskite film's crystallization at a low temperature, the cross-linking product of FB-TA can passivate the grain boundaries and reduce the film's residual strain and Young's module. Then, FB-TA is also introduced for the bottom- and top-interface modification of the perovskite film. The interfacial treating strategy protects the perovskite from water invasion and strengthens the interfaces. The combination of triple strategies affords highly efficient inverted fPSCs with a champion efficiency of 21.42% among the state-of-the-art inverted fPSCs based on nickel oxides. More importantly, the flexible devices also exhibit superior stabilities with T90 >4000 bending cycles, photostability with T90 >568 h, and ambient stability with T90 >2000 h, especially the stability with T80 >1120 h under harsh damp-heat conditions (i.e., 85 °C and 85% RH). The strategy provides new insights into the industrialization of high-performance and stable fPSCs.

Application of Through Glass Via (TGV) Technology for Sensors Manufacturing and Packaging.

Glass has emerged as a highly versatile substrate for various sensor and MEMS packaging applications, including electromechanical, thermal, optical, biomedical, and RF devices, due to its exceptional properties such as high geometrical tolerances, outstanding heat and chemical resistance, excellent high-frequency electrical properties, and the ability to be hermetically sealed. In these applications, Through Glass Via (TGV) technology plays a vital role in manufacturing and packaging by creating electrical interconnections through glass substrates. This paper provides a comprehensive summary of the research progress in TGV fabrication along with its integrations, including through via formation and metallization. This paper also reviews the significant qualification and reliability achievements obtained by the scientific community for TGV technology. Additionally, this paper summarizes the application of TGV technology in various sensors such as MEMS sensors and discusses the potential applications and future development directions of TGV technology.

Development of a Reliable High-Performance WLP for a SAW Device.

In this paper, we present wafer-level packaging technology for surface acoustic wave (SAW) filters with higher long-term reliability and better electrical performance. This article focuses on the package structure, fabrication processes, and reliability for the SAW filter wafer-level package (WLP). The key processes, including cavity wall (CW) dam formation through non-photosensitive film vias development using a laser drilling process, a redistribution layer (RDL), and ball-grid array formation are developed. In addition, a numerical study based on the finite element model has been conducted to analyze the stress distribution of Cu RDL traces. In addition, the CW dam and the roof layer are covered with polymer, which solves the delamination problem between the CW dam and the substrate. Meanwhile, after practical verification, the SAW filter WLP was resistant to encapsulating pressure using a high elastic modulus capping material, which solved the collapse problem. Additionally, a comparison of the RF filter package's electrical performance following the preconditional level 3 and unbiased highly accelerated stress test revealed no differences in insertion attenuation across the passband (<0.2 dB, standard value: 1 dB). The final packages passed the reliability tests in the field of consumer electronics.

Development of 3D Wafer Level Hermetic Packaging with Through Glass Vias (TGVs) and Transient Liquid Phase Bonding Technology for RF Filter.

The development of 5G mobile communication created the need for high-frequency communication systems, which require vast quantities of radio frequency (RF) filters with a high-quality factor (Q) and low inband losses. In this study, the packaging of an RF filter with a through-glass via (TGV) interposer was designed and fabricated using a three-dimensional wafer-level package (3D WLP). TGV fabrication is a high-yielding process, which can produce high precision vias without masking and lithography and reduce the manufacturing cost compared with the through silicon via (TSV) solution. The glass interposer capping wafer contains Cu-filled TGV, a metal redistribution layer (RDL), and the bonding layer. The RF filter substrate with Au bump is bonded to the capping wafer based on Au-Sn transient liquid phase (TLP) bonding at 280 °C with a 40 kN (approximately 6.5 MPa) bonding force. Experimental results show that shear strengths of approx. 54.5 MPa can be obtained, higher than the standard requirement (~6 MPa). In addition, a comparison of the electrical performance of the RF filter package after the pre-conditional level three (Pre-Con L3) and unbiased highly accelerated stress (uHAST) tests showed no difference in insertion attenuation across the passband (<0.2 dB, standard value: <1 dB). The final packages passed the reliability tests in the field of consumer electronics. The proposed RF filter WLP achieves high performance, low cost, and superior reliability.

Development of Reliable, High Performance WLCSP for BSI CMOS Image Sensor for Automotive Application.

To meet the urgent market demand for small package size and high reliability performance for automotive CMOS image sensor (CIS) application, wafer level chip scale packaging (WLCSP) technology using through silicon vias (TSV) needs to be developed to replace current chip on board (COB) packages. In this paper, a WLCSP with the size of 5.82 mm × 5.22 mm and thickness of 850 µm was developed for the backside illumination (BSI) CIS chip using a 65 nm node with a size of 5.8 mm × 5.2 mm. The packaged product has 1392 × 976 pixels and a resolution of up to 60 frames per second with more than 120 dB dynamic range. The structure of the 3D package was designed and the key fabrication processes on a 12" inch wafer were investigated. More than 98% yield and excellent optical performance of the CIS package was achieved after process optimization. The final packages were qualified by AEC-Q100 Grade 2.

Optical Amplification at 1.5 µm in ErIII Coordination Polymer-Doped Waveguides Based on Intramolecular Energy Transfer.

9,9-bis (diphenylphosphorylphenyl) fluorene (FDPO) and dibenzotetrathienoacene (DBTTA), are synthesized as the neutral and anionic ligands, respectively, to prepare the ErIII coordination polymer [Er(DBTTA)3(FDPO)]n. Based on the intramolecular energy transfer, optical gains at 1.5 µm are demonstrated in [Er(DBTTA)3(FDPO)]n-doped polymer waveguides under excitations of low-power light-emitting diodes (LEDs) instead of laser pumping. A ligand-sensitization scheme between organic ligands and Er3+ ions under an excitation of an ultraviolet (UV) LED is established. Relative gains of 10.5 and 8.5 dB cm-1 are achieved at 1.53 and 1.55 µm, respectively, on a 1-cm-long SU-8 channel waveguide with a cross-section of 2 × 3 µm2 and a 1.5-µm-thick [Er(DBTTA)3(FDPO)]n-doped polymethylmethacrylate (PMMA) as upper cladding. The ErIII coordination polymer [Er(DBTTA)3(FDPO)]n can be conveniently integrated with various low-loss inorganic waveguides to compensate for optical losses in the C-band window. Moreover, by relying on the intramolecular energy transfer and UV LED top-pumping technology, it is easy to achieve coupling packaging of erbium-doped waveguide amplifiers (EDWAs) with pump sources in planar photonic integrated chips, effectively reducing the commercial costs.

High-Gain of NdIII Complex Doped Optical Waveguide Amplifiers at 1.06 and 1.31 µm Wavelengths Based on Intramolecular Energy Transfer Mechanism.

Chelate phosphine oxide ligand (9,9-dimethyl-9H-xanthene-4,5-diyl) bis (diphenylphosphineoxide) (XPO) is prepared as a neutral ligand to synthesize complex Nd (TTA)3 (XPO) (TTA = 2-thenoyltrifluoroacetone). An appropriate energy gap between the XPO and TTA ligands, which can support two additional energy transfer routines from the first excited triplet state (T1 ) energy level of the XPO to that of the TTA, improves energy transfer in the Nd complex. Based on intramolecular energy transfer mechanism, optical gains at 1.06 and 1.31 µm are demonstrated in Nd (TTA)3 (XPO)-doped polymer waveguides with the excitation of low-power light-emitting diodes (LEDs) instead of semiconductor lasers as pump sources. Using the vertical top-pumping mode of a 365 nm LED, relative gains of 22.5 and 8.4 dB cm-1 are obtained at 1.06 and 1.31 µm, respectively, in a 0.2 cm long embedded waveguide with a cross-section of 8 × 5 µm2 . The active core layer is Nd (TTA)3 (XPO)-doped SU-8 polymer. Moreover, relative gains are achieved in evanescent-field waveguide with a cross-section of 6 × 4 µm2 . The 21.0 and 5.6 dB cm-1 relative gains are achieved at 1.06 and 1.31 µm, respectively, with a net gain of 13.8 ± 0.3 dB cm-1 obtained at 1.06 µm in a 0.9 cm long SU-8 waveguide with Nd (TTA)3 (XPO)-doped polymethylmethacrylate as upper cladding.

Thermo-Mechanical Reliability Study of Through Glass Vias in 3D Interconnection.

Three-dimensional (3D) interconnection technology based on glass through vias (TGVs) has been used to integrate passive devices, and optoelectronic devices due to its superior electrical qualities, outstanding mechanical stability, and lower cost. Nevertheless, the performance and reliability of the device will be impacted by the thermal stress brought on by the mismatch of the coefficient of thermal expansion among multi-material structures and the complicated structure of TGV. This paper focuses on thermal stress evolution in different geometric and material parameters and the development of a controlled method for filling polymers in TGV interconnected structures. In addition, a numerical study based on the finite element (FE) model has been conducted to analyze the stress distribution of the different thicknesses of TGV-Cu. Additionally, a TGV interconnected structure model with a polymer buffer layer is given to solve the crack problem appearing at the edge of RDL. Meanwhile, after practical verification, in comparison to the experimental results, the FE model was shown to be highly effective and accurate for predicting the evolution of stress, and several recommendations were made to alleviate stress-related reliability concerns. An improved manufacturing process flow for the TGV interconnected structure was proposed and verified as feasible to address the RDL crack issue based on the aforementioned research. It provides helpful information for the creation of highly reliable TGV connection structures.

Sensorized guidewires with MEMS tri-axial force sensor for minimally invasive surgical applications.

This paper describes the design of a tri-axial microelectromechanical force sensor (FS) that can be mounted on the tip of the guidewire. Piezoresistive silicon nanowires (SiNW) are embedded into a cross cantilever design with a manoeuvrable stylus to allow the detection of force in all directions. The electrical resistance changes in the four SiNWs are used to decode an arbitrary force applied onto the FS. The sensitivity of the device can be improved by two orders of magnitude compared to bulk Si thanks to the giant piezoresistive effects offered by the SiNW. Robustness of the FS is improved due to the novel design by incorporating a mechanical stopper at the tip of the stylus. Finite element analysis (FEM) analysis was used in designing the FS.