Thin-Film Copper Indium Gallium Selenide Solar Cell Based on Low-Temperature All-Printing Process

In the solar cell field, development of simple, low-cost, and low-temperature fabrication processes has become an important trend for energy-saving and environmental issues. Copper indium gallium selenide (CIGS) solar cells have attracted much attention due to the high absorption coefficient, tunable band gap energy, and high efficiency. However, vacuum and high-temperature processing in fabrication of solar cells have limited the applications. There is a strong need to develop simple and scalable methods. In this work, a CIGS solar cell based on all printing steps and low-temperature annealing is developed. CIGS absorber thin film is deposited by using dodecylamine-stabilized CIGS nanoparticle ink followed by printing buffer layer. Silver nanowire (AgNW) ink and sol–gel-derived ZnO precursor solution are used to prepare a highly conductive window layer ZnO/[AgNW/ZnO] electrode with a printing method that achieves 16 Ω/sq sheet resistance and 94% transparency. A CIGS solar cell based on all printing processes exhibits efficiency of 1.6% with open circuit voltage of 0.48 V, short circuit current density of 9.7 mA/cm², and fill factor of 0.34 for 200 nm thick CIGS film, fabricated under ambient conditions and annealed at 250 °C

Growth and Extension of One-Step Sol–Gel Derived Molybdenum Trioxide Nanorods via Controlling Citric Acid Decomposition Rate

A simple sol–gel solution route for the synthesis of α-phase molybdenum trioxide (α-MoO₃) nanorods is investigated in terms of growth mechanism with controlling the citric acid decomposition rate. The single-phase and single-crystal nanorod arrays of MoO₃ grown in random directions from a silica glass substrate had mean diameters and lengths of 10 and 500 nm, respectively, as determined through chemical analysis. The citric acid plays a critical role for the nanorods growth process from investigating the relative molar ratio of molybdate and citric acid in the precursor. Moreover, the dissociation timing of the citric acid, which was controlled by the other two synthesis parameters, i.e., sintering time and solvents, also greatly influences growth and phase transition of the MoO₃ nanorods, which was analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The synthesis parameters were optimized to design the length and density of the nanorod arrays. The longest nanorods can be obtained up to 600 nm using a dimethylacetamide solvent, a molar ratio of Mo:citric acid = 0.5:1.5, and sintering at 673 K for 15 min in an ambient atmosphere. Findings of the present study describe that the factors of the nanorods’ growth and phase changing are deeply correlated with disassemble steps of the Mo metal–citric acid complex in the sol–gel precursor solution, which may contribute to applying the material development in several electronic devices using MoO₃ nanostructures

Highly Reliable Silver Nanowire Transparent Electrode Employing Selectively Patterned Barrier Shaped by Self-Masked Photolithography

The transparent electrode based on silver nanowire (AgNW) networks is one promising alternative of indium tin oxide film in particular for advanced flexible and printable electronics. However, the widespread application of AgNW electrode is hindered by its poor long-term reliability. Although the reliability can be improved by applying traditional overcoating layer or the core–shell structure, the transmittance or conductivity is inevitably undermined. In this paper, a novel patterned barrier of photoresist in situ assembled on the nanowire surface realized the reliability enhancement by simply employing AgNWs themselves as the mask in the photolithography process. The patterned barrier selectively covered the nanowires, while keeping the high transmittance and conductivity unchanged and improving the adhesion of AgNW networks on substrate. After 720 h storage in 85 °C/85% relative humidity (RH) environment, the resistance of electrode with patterned barrier only increased by 0.72 times. This study proposes a new way, i.e., the in situ patterned barrier containing light-sensitive substance, to selectively protect AgNW networks, which can be expanded to various metallic networks including nanowires, nanorods, nanocables, electrospun nanofibers, and so on

Cu Salt Ink Formulation for Printed Electronics using Photonic Sintering

We formulate copper salt (copper formate/acetate/oleate) precursor inks for photonic sintering using high-intensity pulsed light (HIPL) based on the ink’s light absorption ability. The inks can be developed through controllable crystal field splitting states (i.e., the ligand weights and their coordination around the metal centers). The inks’ light absorption properties are extremely sensitive to the carbon chain lengths of the ligands, and the ink colors can drastically change. From the relationship between the ratios of C/Cu and the required sintering energies, it is possible to ascertain that the integral absorbance coefficients are strongly correlated with the photonic sintering behavior. These results suggest that the ink absorbance properties are the most important factors in photosintering. The wires formed by sintered copper formate complex ink via the HIPL method showed good electronic conduction, achieving a low resistivity of 5.6 × 10^–5 Ω cm. However, the resistivity of the wires increased with increasing contains carbon chain length of the inks, suggesting that large amounts of residual carbon have negative effects on both the wire’s surface morphology and the electrical conductivity. We find in this study that high light absorptivity and low carbon inks would lead to a lower environmental load in future by reducing both energy usage and carbon oxide gas emissions

Printable and Flexible Copper–Silver Alloy Electrodes with High Conductivity and Ultrahigh Oxidation Resistance

Printable and flexible Cu–Ag alloy electrodes with high conductivity and ultrahigh oxidation resistance have been successfully fabricated by using a newly developed Cu–Ag hybrid ink and a simple fabrication process consisting of low-temperature precuring followed by rapid photonic sintering (LTRS). A special Ag nanoparticle shell on a Cu core structure is first created in situ by low-temperature precuring. An instantaneous photonic sintering can induce rapid mutual dissolution between the Cu core and the Ag nanoparticle shell so that core–shell structures consisting of a Cu-rich phase in the core and a Ag-rich phase in the shell (Cu–Ag alloy) can be obtained on flexible substrates. The resulting Cu–Ag alloy electrode has high conductivity (3.4 μΩ·cm) and ultrahigh oxidation resistance even up to 180 °C in an air atmosphere; this approach shows huge potential and is a tempting prospect for the fabrication of highly reliable and cost-effective printed electronic devices

One-Step Fabrication of Stretchable Copper Nanowire Conductors by a Fast Photonic Sintering Technique and Its Application in Wearable Devices

Copper nanowire (CuNW) conductors have been considered to have a promising perspective in the area of stretchable electronics due to the low price and high conductivity. However, the fabrication of CuNW conductors suffers from harsh conditions, such as high temperature, reducing atmosphere, and time-consuming transfer step. Here, a simple and rapid one-step photonic sintering technique was developed to fabricate stretchable CuNW conductors on polyurethane (PU) at room temperature in air environment. It was observed that CuNWs were instantaneously deoxidized, welded and simultaneously embedded into the soft surface of PU through the one-step photonic sintering technique, after which highly conductive network and strong adhesion between CuNWs and PU substrates were achieved. The CuNW/PU conductor with sheet resistance of 22.1 Ohm/sq and transmittance of 78% was achieved by the one-step photonic sintering technique within only 20 μs in air. Besides, the CuNW/PU conductor could remain a low sheet resistance even after 1000 cycles of stretching/releasing under 10% strain. Two flexible electronic devices, wearable sensor and glove-shaped heater, were fabricated using the stretchable CuNW/PU conductor, demonstrating that our CuNW/PU conductor could be integrated into various wearable electronic devices for applications in food, clothes, and medical supplies fields

One-Step Fabrication of Stretchable Copper Nanowire Conductors by a Fast Photonic Sintering Technique and Its Application in Wearable Devices

Copper nanowire (CuNW) conductors have been considered to have a promising perspective in the area of stretchable electronics due to the low price and high conductivity. However, the fabrication of CuNW conductors suffers from harsh conditions, such as high temperature, reducing atmosphere, and time-consuming transfer step. Here, a simple and rapid one-step photonic sintering technique was developed to fabricate stretchable CuNW conductors on polyurethane (PU) at room temperature in air environment. It was observed that CuNWs were instantaneously deoxidized, welded and simultaneously embedded into the soft surface of PU through the one-step photonic sintering technique, after which highly conductive network and strong adhesion between CuNWs and PU substrates were achieved. The CuNW/PU conductor with sheet resistance of 22.1 Ohm/sq and transmittance of 78% was achieved by the one-step photonic sintering technique within only 20 μs in air. Besides, the CuNW/PU conductor could remain a low sheet resistance even after 1000 cycles of stretching/releasing under 10% strain. Two flexible electronic devices, wearable sensor and glove-shaped heater, were fabricated using the stretchable CuNW/PU conductor, demonstrating that our CuNW/PU conductor could be integrated into various wearable electronic devices for applications in food, clothes, and medical supplies fields