A Modified Sequential Deposition Route for High-Performance Carbon-Based Perovskite Solar Cells under Atmosphere Condition

Carbon-based hole transport material (HTM)-free perovskite solar cells have exhibited a promising commercialization prospect, attributed to their outstanding stability and low manufacturing cost. However, the serious charge recombination at the interface of the carbon counter electrode and titanium dioxide (TiO2) suppresses the improvement in the carbon-based perovskite solar cells’ performance. Here, we propose a modified sequential deposition process in air, which introduces a mixed solvent to improve the morphology of lead iodide (PbI2) film. Combined with ethanol treatment, the preferred crystallization orientation of the PbI2 film is generated. This new deposition strategy can prepare a thick and compact methylammonium lead halide (MAPbI3) film under high-humidity conditions, which acts as a natural active layer that separates the carbon counter electrode and TiO2. Meanwhile, the modified sequential deposition method provides a simple way to facilitate the conversion of the ultrathick PbI2 capping layer to MAPbI3, as the light absorption layer. By adjusting the thickness of the MAPbI3 capping layer, we achieved a power conversation efficiency (PCE) of 12.5% for the carbon-based perovskite solar cells.

Tailoring capping-layer composition for improved stability of mixed-halide perovskites

Incorporating a low dimensional (LD) perovskite capping layer on top of perovskite absorber, improves the stability of perovskite solar cells (PSCs). However, in the case of mixed-halide perovskites, which can...

Comparative Study of the New Type Capping Layer for Hf0.5Zr0.5O2 Ferroelectric Film

The capping layers have great influences on the ferroelectricity of the Hf0.5Zr05O2 (HZO) film during annealing process. In this paper we compared the properties of the HZO film with two inorganic nonmetallic capping layers and no capping layer. The remnant (2Pr) of HZO films are 23.5 uC/cm2, 27.3 uC/cm2 and 20.3 uC/cm2 for no capping layer, Si3N4 capping layer and SiO2 capping layer, respectively. The capping layer can change the direction of the coercive filed shift even though the capacitors have the same metal electrodes.

Bimetallic structures to enhance the performance of surface plasmon resonance sensors

<p><b>Surface plasmon resonance (SPR) sensing is a label−free and rapid detection method and has extensive applications in the field of medical diagnostics, food control, and environmental monitoring. However, the lack of sensitivity to detect small molecules is a continuing concern in the application of this technique. Past research has explored different plasmonic structures such as metal nanoparticles, metallic nanoslits, nanoholes, colloidal Au nanoparticles, 2D nanomaterials, and multilayer structures as the sensing layer to improve the sensitivity of these sensors. However, the sensitivity improvement could be realised only with the cost of the increased complexity of optical configuration and sensor chip fabrication. Silver (Ag) is a very good candidate as the metallic layer for the sensor chip due to its higher electrical conductivity as compared to gold (Au). Besides cost−effectiveness, Ag thin film based sensors have better sensitivity with a sharp resonance dip and a high signal−to−noise ratio. However, the poor chemical stability of Ag thin films prevents their use in practical applications. Noble metals such as Au and platinum (Pt) offer greatly enhanced chemical stability. This work investigated the development of SPR sensors composed of a silver−noble metal bilayer structure to utilize both the sensitivity of silver and the chemical stability of the noble metal.</b></p> <p>To enable this research, an automated experimental SPR testbed for sensor characterisation was designed and constructed. This testbed is based on the Kretschmann configuration, using a He−Ne laser source at 632.8 nm. SPR sensor consisting of multilayer metal structures was fabricated using standard microelectronic fabrication techniques.</p> <p>The influence of the relative thickness of a noble metal capping layer on the SPR response and sensitivity from the Ag layer was systematically optimised, using both theoretical and experimental approaches. A theoretical analysis of the performance of the bimetallic SPR sensors was done using the transfer matrix method (TMM) by assuming a five−layer configuration. In the case of an Au capping layer, these simulations indicate an optimised thickness of 45 nm for Ag and 5 nm for Au. The observation from experimental analysis of different thickness combinations of Ag and Au matched the simulated results. However, the results of the stability studies exclude the practical use of 45 nm Ag/5 nm Au structures, as long−term degradation of the Ag layer occurs. A structure of 40 nm Ag/10nm Au was thus selected as the best composition for sensor applications. It is showed that sensors fabricated with this structure showed enhanced sensitivity compared to single−layer Au sensors, with a sensitivity 50% higher than that of the single−layer Au sensor. In the case of Ag/Pt structures, simulations indicated enhanced sensitivity from a 10 nm Ag/16 nm Pt structure. However, experimental measurements did not show any evidence for SPP excitation of Pt at the measured wavelength of 632.8 nm, making it unsuitable as a capping layer in our studies.</p> <p>The application of 40 nm Ag/10 nm Au bimetal layers as biosensors was done by the immobilization of thiol−terminated vitamin B12 aptamers on the Au sensor surface. However, the results were not reproducible, and more work on the binding kinetics of this aptamer will need to be performed to use this in a biosensor structure.</p>

Bimetallic structures to enhance the performance of surface plasmon resonance sensors

<p><b>Surface plasmon resonance (SPR) sensing is a label−free and rapid detection method and has extensive applications in the field of medical diagnostics, food control, and environmental monitoring. However, the lack of sensitivity to detect small molecules is a continuing concern in the application of this technique. Past research has explored different plasmonic structures such as metal nanoparticles, metallic nanoslits, nanoholes, colloidal Au nanoparticles, 2D nanomaterials, and multilayer structures as the sensing layer to improve the sensitivity of these sensors. However, the sensitivity improvement could be realised only with the cost of the increased complexity of optical configuration and sensor chip fabrication. Silver (Ag) is a very good candidate as the metallic layer for the sensor chip due to its higher electrical conductivity as compared to gold (Au). Besides cost−effectiveness, Ag thin film based sensors have better sensitivity with a sharp resonance dip and a high signal−to−noise ratio. However, the poor chemical stability of Ag thin films prevents their use in practical applications. Noble metals such as Au and platinum (Pt) offer greatly enhanced chemical stability. This work investigated the development of SPR sensors composed of a silver−noble metal bilayer structure to utilize both the sensitivity of silver and the chemical stability of the noble metal.</b></p> <p>To enable this research, an automated experimental SPR testbed for sensor characterisation was designed and constructed. This testbed is based on the Kretschmann configuration, using a He−Ne laser source at 632.8 nm. SPR sensor consisting of multilayer metal structures was fabricated using standard microelectronic fabrication techniques.</p> <p>The influence of the relative thickness of a noble metal capping layer on the SPR response and sensitivity from the Ag layer was systematically optimised, using both theoretical and experimental approaches. A theoretical analysis of the performance of the bimetallic SPR sensors was done using the transfer matrix method (TMM) by assuming a five−layer configuration. In the case of an Au capping layer, these simulations indicate an optimised thickness of 45 nm for Ag and 5 nm for Au. The observation from experimental analysis of different thickness combinations of Ag and Au matched the simulated results. However, the results of the stability studies exclude the practical use of 45 nm Ag/5 nm Au structures, as long−term degradation of the Ag layer occurs. A structure of 40 nm Ag/10nm Au was thus selected as the best composition for sensor applications. It is showed that sensors fabricated with this structure showed enhanced sensitivity compared to single−layer Au sensors, with a sensitivity 50% higher than that of the single−layer Au sensor. In the case of Ag/Pt structures, simulations indicated enhanced sensitivity from a 10 nm Ag/16 nm Pt structure. However, experimental measurements did not show any evidence for SPP excitation of Pt at the measured wavelength of 632.8 nm, making it unsuitable as a capping layer in our studies.</p> <p>The application of 40 nm Ag/10 nm Au bimetal layers as biosensors was done by the immobilization of thiol−terminated vitamin B12 aptamers on the Au sensor surface. However, the results were not reproducible, and more work on the binding kinetics of this aptamer will need to be performed to use this in a biosensor structure.</p>