台大光电所所讯

Surface plasmons coupled two-dimensional photonic crystal biosensors for Epstein-Barr virus protein detection

Professor Jian-Jang Huang

Graduate Institute of Photonics and Optoelectronics, National Taiwan University

台湾大学光电所黄建璋教授

The fundamental detection scheme of typical grating or photonic crystal (PhC) sensors relies on the correlation of the diffraction behaviors with the refractive index of target analyte. For biomaterial detection, a thin gold film is usually deposited on the sensor surface so that cross linkers can be anchored before functionalizing the device. The nanoscale metallic film suggests plasmonic resonances play a critical role in light-matter interaction. In this work, we demonstrated a compact two-dimensional (2D) hexagonal photonic crystal (PhC) biosensor with thin gold film coating. In such a device, surface plasmon polariton (SPP) on the metal structure and phase matching of optical wave with the PhC are considered when analyzing light-biomaterial interaction on the detector. Using Epstein-Barr nuclear antigen-1 (EBNA-1) antibody as an example, protein sensing along different lattice orientations of the PhC biosensor was investigated. Based on the dispersion relationship and phase matching conditions, we unravel the mechanisms involved in the wavelength shifts and sensitivities. The simulation results verify the phenomenon of tighter spatial confinement and higher local field intensity from the SPP, which helps detecting small variations of the refractive index on the sensor surface.

Fig. 1 Experimental setup for characterizing EBNA-1 antibodies

Fig. 2 (a) Sensitivity curves (cut-off wavelength shifts of various EBNA-1 antibody concentrations) along (a) G_k and (b) G_m directions

Fig. 3 Simulation results of a EM field within a single nanohole

In-situ CH₃NH₃PbI₃ Interface Treatment by Dielectric Barrier Discharge Plasma for Perovskite Solar Cells

Professor I-Chun Cheng

Graduate Institute of Photonics and Optoelectronics, National Taiwan University

台湾大学光电所陈奕君教授

The surface diffusion dielectric barrier discharge (SDDBD) is a type of low-temperature plasma operated at regular pressure without the requirement of vacuum pumps and chambers. The plasma is formed by applying an AC voltage to produce a filamentous discharge. In this work, the effect of surface diffusion dielectric barrier discharge treatment on the properties of methylammonium lead iodide (CH₃NH₃PbI₃) perovskite thin films is investigated. The in-situ SDDBD-treated MAPbI₃ perovskite thin films are then used as the absorber layers for planar n-i-p perovskite solar cells (PSCs). N-O emission system is observed in the plasma during the treatment, indicating the reactions of reactive nitrogen plasma species with the organics in the precursor films. Long SDDBD treatment duration (60 s) leads to the phase precipitation of PbI₂ and degrades the cell efficiency, whereas short SDDBD treatment duration (20 s) significantly improves the PSC efficiency by nearly 40%. Only slight performance enhancement is observed in the PSCs prepared by conventional thermal treatment at the same substrate temperatures as that for SDDBD treatment, implying that SDDBD provides the synergetic effect of the reactivity and plasma heating. Electrochemical impedance spectroscopy indicates that the charge recombination impedance increases and then decreases with SDDBD treatment duration. The shunt resistance also shows a similar trend, and it is consistent with the PSC performance. The PSC with the 20 s SDDBD-treated absorber layer shows energy conversion efficiency of 14.29%, open circuit voltage of 1.022 V, short circuit current density of 19.45 mA/cm², and fill factor of 0.72, whereas the corresponding values for the untreated counterpart are 10.32%, 0.976 V, 18.52 mA/cm², and 0.57. The result shows that short-duration low-temperature SDDBD treatment effectively enhances the performance of solution processed PSCs. [Appl. Surf. Sci. 473, pp.468 – 475, 2019.]

Fig. 1. (a) Evolution of OES of SDDBD plasmas during the treatment for perovskite layers. (b) J-V curves of PSCs with various SDDBD treatment conditions.