Lcr meter 4284a

We use a single-component nematic LC, 4′-butyl-4-heptyl-bicyclohexyl-4-carbonitrile, abbreviated as CCN-47 (Nematel GmbH). The conductivity was adjusted by adding 0.005 wt% TBABr, produced by Sigma-Aldrich, using chloroform as a solvent. Chloroform was evaporated in the vacuum oven for 24 h at the room temperature and then for another 24 h at 60 °C. We measured the anisotropy of both permittivity and conductivity by an LCR meter 4284A (Hewlett–Packard) using cells with planar and homeotropic alignment using polyimides AL1254 and JALS-204, respectively (both are purchased from Japan Synthetic Rubber Co.). The principal components of conductivity and dielectric permittivity tensors of doped CCN-47 are σ_∥ ≈ 1.6 × 10⁻⁸ Ω⁻¹ m⁻¹, σ_⊥ ≈ 1.8 × 10⁻⁸ Ω⁻¹ m⁻¹, ε_∥ ≈ 4.9, and ε_⊥ ≈ 8.2 at 5 kHz and 55 °C; the subscripts indicate whether the property is measured along the background director ${\widehat{\mathbf{n}}}_0$ or perpendicularly to it.

The studied nematic is a single-component 4′-butyl-4-heptyl-bicyclohexyl-4-carbonitrile, abbreviated as CCN-47 (Nematel GmbH). The phase diagram of CCN-47 is smectic A 29.9 °C nematic 58.5 °C isotropic phase. We confirmed the conclusion of Dhara and Madhusudana^{32 (link)} that the anisotropy of both the permittivity and conductivity of CCN-47 is negative, by performing independent measurements using an LCR meter 4284A (Hewlett-Packard), and cells with planar (alignment agent polyimide PI-2555, HD MicroSystems) and homeotropic (polyimide SE1211) alignment. In particular, at 45 °C and 4 kHz, ε_⊥ ≈ 8.8, ε_∥ ≈ 4.6, σ_⊥ ≈ 6.1 × 10⁻⁹ Ω⁻¹ m⁻¹, σ_|| ≈ 4.9 × 10⁻⁹ Ω⁻¹ m⁻¹ and concentration of ions is 4 × 10²⁰ m⁻³. The effective viscosities of CCN- 47 are η_|| = 57 mPa s and η_⊥ = 58 mPa s for a motion parallel and perpendicular to the director, respectively, as determined by tracking Brownian motion of polystyrene colloidal spheres of diameter 5 μm and tangential surface anchoring^{41 (link)}.

The EQE spectra were recorded in a N₂ glovebox using an Enli Technology (Taiwan) EQE measurement system (QE‐R) in AC mode under illumination with monochromatic light from a xenon arc lamp, and the light intensity at each wavelength was calibrated with a standard Si photovoltaic cell. The current‐voltage curves in the dark were measured in ambient air using a source meter (Keithley 4200) without irradiation with forward (−1 to 1 V) scans, and the step voltage was fixed at 20 mV. The photo‐response curves of photodiodes under a pulse laser (532 nm) were measured using a mixed domain oscilloscope (Tektronix, MDO3034). The capacitance–voltage curves in the dark were measured using a precision LCR meter 4284A (Hewlett‐Packard, Japan). All the photodiodes had no encapsulation and employed a mask with an aperture area of 0.11 cm² when depositing metal electrode.