Optoelectronic Attributes Research Articles

Midinfrared Electro-optic Modulation in Few-Layer Black Phosphorus.

Black phosphorus stands out from the family of two-dimensional materials as a semiconductor with a direct, layer-dependent bandgap spanning the visible to mid-infrared (mid-IR) spectral range. It is, therefore, a very promising material for various optoelectronic applications, particularly in the important mid-IR range. While mid-IR technology has been advancing rapidly, both photodetection and electro-optic modulation in the mid-IR rely on narrow-band compound semiconductors, which are difficult and expensive to integrate with the ubiquitous silicon photonics. For mid-IR photodetection, black phosphorus has already been proven to be a viable alternative. Here, we demonstrate electro-optic modulation of mid-IR absorption in few-layer black phosphorus. Our experimental and theoretical results find that, within the doping range obtainable in our samples, the quantum confined Franz-Keldysh effect is the dominant mechanism of electro-optic modulation. A spectroscopic study on samples with varying thicknesses reveals strong layer dependence in the interband transition between specific pairs of sub-bands. Our results show that black phosphorus is a very promising material to realizing efficient mid-IR modulators.

Systematics in morphological, structural and optoelectrical properties of nanocrystalline CdS thin films grown by electrodeposition method

In this study, high-quality nanocrystalline CdS films are prepared on fluorine doped tin oxide (FTO) FTO/glass substrates by electrodeposition method. The properties of annealed CdS film are optimized for estimating required thickness and nano-sized grain morphology with better optoelectronic attributes at optimum growth voltages. Field emission SEM images indicate CdS films with compact and nanosized grains are obtained even after a long deposition time at optimized growth voltages. X-ray diffraction reveals the films are polycrystalline in nature with a hexagonal wurtzite structure. CdS layer thickness is obtained by cross-sectional SEM images and compared with estimates from weight gain measurements and Faraday equation. Thicknesses of about 70–100nm within 75–120s are obtained. Energy dispersive X-ray (EDX) analyses for elemental analysis indicate very pure CdS layers. UV–Vis spectroscopy is applied to calculate the band gap. The sheet resistance of the films is also measured by four-point probe method.

High Photoluminescence Quantum Yield in Band Gap Tunable Bromide Containing Mixed Halide Perovskites.

Hybrid organic-inorganic halide perovskite based semiconductor materials are attractive for use in a wide range of optoelectronic devices because they combine the advantages of suitable optoelectronic attributes and simultaneously low-cost solution processability. Here, we present a two-step low-pressure vapor-assisted solution process to grow high quality homogeneous CH3NH3PbI3-xBrx perovskite films over the full band gap range of 1.6-2.3 eV. Photoluminescence light-in versus light-out characterization techniques are used to provide new insights into the optoelectronic properties of Br-containing hybrid organic-inorganic perovskites as a function of optical carrier injection by employing pump-powers over a 6 orders of magnitude dynamic range. The internal luminescence quantum yield of wide band gap perovskites reaches impressive values up to 30%. This high quantum yield translates into substantial quasi-Fermi level splitting and high "luminescence or optically implied" open-circuit voltage. Most importantly, both attributes, high internal quantum yield and high optically implied open-circuit voltage, are demonstrated over the entire band gap range (1.6 eV ≤ Eg ≤ 2.3 eV). These results establish the versatility of Br-containing perovskite semiconductors for a variety of applications and especially for the use as high-quality top cell in tandem photovoltaic devices in combination with industry dominant Si bottom cells.

The predictions of optoelectronic attributes of LED by neural network

In this paper, the predictions of optoelectronic attributes of Light-Emitting Diode (LED) chip, including luminous intensity, wavelength and forward voltage by using neural network were presented. The simulated data was measured by Electrical Luminescence (EL) technique. The well-trained neural models were used to predict the optoelectronic attributes of LED chip in its epitaxy growth stage in advance. These predicted results could provide the necessary information for the process engineer to adjust the control parameters of epitaxy growth accurately and then ensure the LED chip to be in conformance with the requested quality.