Light Injection Research Articles

Probing the stability of perovskite solar cell under working condition through an ultra-thin silver electrode: Beyond the halide ion diffusion and metal diffusion

Perovskite solar cells (PSCs) with an excellent optoelectronic performance have intrigued mushrooming research interests, and the undesirable intrinsic stability of halide perovskite materials still remains a severe constraint for their practical application. Fortunately, the ambiguous and complicated incentives for the degradation process of PSCs under working condition can be directly reflected on the corrosion of silver electrode by halogens. Here, a new perspective for evaluating the long-term stability of PSCs is presented by the time-dependent transverse resistance of the ultrathin silver electrode under different working conditions. Being anode or cathode, the stability of ultra-thin silver layer has been systematically investigated through adjusting the external operating conditions of devices, i.e. light illumination and bias voltage. Experimental results indicate that the gradual resistance increases of silver film can be attributed to the oxidation of I− existing on the top surface of perovskite layer by non-equilibrium holes generated from light illumination or electrical injection for producing corrosive I2 gas, which will diffuse through the carrier transporting layer and attack the thin silver layer. The interaction probability of I− and non-equilibrium holes at the interface plays a critical role on the generation of I2 gas and resistance variation of the top thin silver electrode. The stability study of electrode indicator will shed light on the ambiguous degradation mechanisms of PSC under working condition, paving a path for conquering the fatal problems of the practical application.

ZnO/Cu2O heterojunction integrated fiber-optic biosensor for remote detection of cysteine

Indium tin oxide, semiconductor nanomaterial ZnO, and Cu2O were first loaded on the surface of the optical fiber to form an optical fiber probe. Large-volume macroscopic spatial light is replaced by an optical fiber path, and remote light injection is implemented. Based on the optical fiber probe, a photoelectrochemical biosensor was constructed and remote detection of cysteine was realized. In this tiny device, the optical fiber probe not only acts as a working electrode to react with the analyte but also directs the light exactly where it is needed. Simultaneously, the electrochemical behavior of cysteine on the surface of the working electrode is dominated by diffusion-control, which provides strong support for quantitative detection. Then, under the bias potential of 0 V, the linear range of the fiber-optic-based cysteine biosensor was 0.01∼1 μM, the regression coefficient (R2) value was 0.9943. In spiked synthetic urine, the detection of cysteine was also realized by the integrated biosensor. Moreover, benefiting from the low optical fiber loss, the new structure also possesses a unique remote detection function. This work confirms that photoelectrochemical biosensors can be integrated via optical fibers and retain comparable sensing performance. Based on this property, different materials can also be loaded on the surface of the optical fiber for remote detection of other analytes. It is expected to facilitate the research on fiber-optic-based integrated biosensors and show application prospects in diverse fields such as biochemical analysis and disease diagnosis.

Imaging sensors for PoET: a spatially resolved solar spectroscopy instrument

The study of the Sun is an area still open in several topics of astrophysics, in a field that has seen an expansion in recent years - therefore, it is critical that collected data is thoroughly traceable and accurate to be used in new study cases or predictive models. A ground based, portable, optimized system, consisting of a Schmidt-Cassegrain telescope coupled to a refractor telescope acting as a pointing telescope, is being designed to provide high resolution imaging of smaller areas on the Sun’s surface, being able to obtain disk-resolved, high spectral resolution data, at a relative low cost (compared to large consortium developed instruments). The light collected by the telescope will be fibre-fed to a spectrograph - the injection of light in the fibre is critical and requires an imaging sensor to aid the light guiding process. The goal of the present work was to explore the best candidates for the image sensors, their architectures, requirements, and constraints, as well as their expected performance range and signal noise. The trade-off analysis between CMOS and CCD based sensors was made and it was concluded, that for the intended application, either type of architecture is admissible, provided the sensor is within desired parameters.

MODERN METHODS OF ROSACEA TREATMENT

Rosacea is a chronic inflammatory dermatosis that mainly affects the cheeks, nose, chin and forehead. Rosacea usually begins between the ages of 30 and 50, but can occur at any age. Population prevalence rates range from < 1 to 22%, but these percentages are likely influenced by differences in study design, methodology, population, geographic location, and cultural and social differences. Rosacea is characterized by recurrent episodes of flushing or transient erythema, persistent erythema, phymatous changes, papules, pustules, and telangiectasia, and the eyes may be involved. Due to the fact that rosacea affects the face, patients with this pathology often have low self-esteem and are prone to anxiety and depression, because this disease has a cosmetic defect. In addition to general skin care, there are several approved treatment options available to address these issues, both topical and systemic. For some functions, intense pulsed light, laser, and surgery are valuable. Recent advances in basic science have highlighted the role of the innate and adaptive immune system, as well as neurovascular dysregulation, underlying the spectrum of clinical manifestations of rosacea. Endogenous and exogenous stimuli can initiate and exacerbate multiple pathways in patients with rosacea.
 With the updated diagnosis and classification of rosacea, treatment options for patients with rosacea have attracted the attention of dermatologists. Here, we summarize the latest advances in the treatment of rosacea, including skin care and cosmetic procedures, topical therapy, oral therapy, laser and light therapy, injection therapy, and combination therapy.

All optical Q-switched laser based spiking neuron

This paper studies theoretically the use of a Q-switch laser with side light injection as a spiking all-optical neuron for photonic spiking neural networks (PSNN). Ordinary differential equations for the multi-section laser are presented, including terms for the side light injection for gain quenching and saturable absorption. The behaviour of the laser mimics that of a spiking neuron with ultrafast pico-second scale response and low power control signals.

Daylighting of road tunnels through external ground-based light-pipes and complex reflective geometry

The transfer of solar light to the interior of tunnels to complement electrical lighting during daytime, contributes to save energy and decrease the number of installed projectors. The solutions traditionally implemented, based on light-pipes hanging from the vault, seemed reasonable because the leakages of light-pipes can emit luminous flux like projectors, but had the disadvantage of needing higher clearance gauges with the consequent costs in drilling, building materials, works and maintenance. Furthermore, these hanging light-pipes cannot be installed in working tunnels if they were not foreseen in the initial project. In this article, a new concept of light injection and distribution in tunnels is proposed. It consists of the coupling of three main elements: collectors, light-pipes, and one reflecting vault whose design is optimized to ensure the photometric requirements on the pavement. The proposed system can collect more than 1.5 Mlm of solar flux with not excessively large collectors installed on the ground of the road shoulder, and project them to the vault that finally distributes the light towards the pavement. With this flux, average illuminances of 3478 lx and uniformities of 0.73 can be achieved, which means pavement luminance around 350–400 cd/m2, in good agreement with the requirements during daytime. The savings can be higher than 40 %. Besides these savings, this system can be easily implemented in existing tunnels. The proposal and some estimations are discussed.

Self-parametric amplification of a bound-state dissipative soliton assisted by spectral filtering effect in the negative dispersion regime

Various striking nonlinear dynamics have been obtained from an ultrafast fiber laser. Herein, we first numerically demonstrate the self-parametric amplification of the bound-state dissipative soliton induced by the spectral filtering effect in the negative dispersion regime. The self-parametric amplification in our work manifests itself as optical spectrum intensity enhancement in the absence of extra pump light injection, which is resulted by the energy flowing within the laser field. Comparing the ultrafast fiber laser system without bandwidth filter and those with 8-nm or 10-nm bandwidth filters respectively, a stable spectrum and two spectral periodic evolutions can be observed, which demonstrates that the spectral filtering effect plays a key role in the self-parametric amplification process. These findings can provide new insights into the complex nonlinear behavior of bound-state dissipative solitons in the ultrafast fiber lasers.

Numerical study on all-optical modulation characteristics of quantum cascade lasers.

To explain the phenomenon of all-optical modulation of quantum cascade laser (QCL), and explore the physics in QCL’s gain medium which consists of multiple of dielectric nanostructures with high refractive index under light injection, we modified the 1½-period model to calculate values of electron population and lifetime in each subband which is separated by the nanostructures, optical gain, current and number of photons in the cavity of a mid-infrared QCL modulated with near-infrared optical injection. The results were consistent with an experiment, where the injected light increases the electron population and lifetime, but does not affect the optical gain obviously. Our study can be helpful for optimizing its use and dielectric nanostructure design.

Theoretical approach for Fe(II/III) and its chlorophyll-related complexes as sensitizers in dye-sensitized solar cells

Dye is the key to the efficiency of harvesting solar energy in dye-sensitized solar cells (DSSCs). The dye performances such as light absorption, electron injection, and electron regeneration depend on the dye molecule structure. To predict it, one needs to compute the optimized molecule geometry, HOMO level, LUMO level, electron density distribution, energy gaps, and dipole moment in the ground and excited state. Chlorophyll-related chlorin and porphyrin, as well as their κ2O,O’ complexes with Fe(II/III), were investigated with density functional theory (DFT) and time-dependent density functional theory (TD-DFT) computations using the B3LYP method and def2-TZVP basis set. NPA charges also were calculated to know the valence of the metal cations exactly. In general, the calculations show that the metal cations introduced occupied d orbitals with lower oxidation potentials than the chlorophyll ligand orbitals, which are responsible for the emergence of additional absorption bands. The states result in effective band broadening and the redshift of spectrum absorbance that is expected to improve DSSC performance.
 Another requirement that has to be possessed is the ability of electron regeneration, electron injection, and dipole moment. The Fe(II) complex has fulfilled these requirements, but not the Fe(III) complex due to having a low electron injection capability. However, this work has shown that Fe(III) complex exhibits a non-innocence ligand. It results in trivalent to divalent state change, in the appearance of a ligand radical cation, an extra hole, and a broader absorption spectrum. It also can affect its other electronic properties, such as electron injection capability. Thus, it can be considered an attractive candidate for the sensitizer in DSSCs

A proposal for optomechanical bichromatic wavelength switching for two-color up-conversion application

This study focuses on the Optomechanical bichromatic wavelength switching system as an indirect two-color up-conversion process that relies on optical force and nanorod scattering effects. This system is used to control light coupling between four parallel optical waveguides made of silicon nitride (Si3N4) which form two identical parts. The parallel waveguides with 0.5 µm × 0.5 µm cross-section and 220 µm lengths are suspended on a silica (SiO2) substrate embedded with the array of square silicon (Si) nanorods. By mid-IR plane wave illumination, as control light, with different intensities and different wavelengths on nanorods, scattering would increase and result in an improvement in attractive gradient optical force exerted on waveguides. Via bending waveguides toward each other, caused by optical gradient force, two different visible lights, as probe signals, propagating in the first waveguide of each section would couple to the adjacent waveguide. Simulation results reveal that when the distance between the parallel waveguides in the equilibrium position is 100 nm and the intensity of mid-IR light is 1.28 mW/µm2 total coupling would occur in two situations: 1- when the control light is 4.5 µm, the probe light with 713 nm wavelength is transmitted to the output, 2- when the control light is 3 µm, the probe light with 609 nm wavelength is transmitted to the output. In the first case 1.92 pN/µm optical force is needed to bend each waveguide by 9 nm and in the second one, 1.28 pN/µm optical force is needed to bend each waveguide by 6 nm for total coupling. The efficiency of the coupled waveguides system is %88.6 for 609 nm probe light injection and %96.5 for 713 nm probe light injection.

Theoretical study on fast and slow light effects in semiconductor optical amplifiers under assist light injection

In this paper, the fast and slow light effect of semiconductor optical amplifiers (SOAs) under assist light injection is theoretically analyzed. Coherent population oscillation (CPO) is used to induce fast and slow light effect in the theoretical model. The effects of parameters such as modulation frequency, modulation current and assist optical power on phase delay are investigated under the assist light injection. These effects are then compared with the case without assist light injection. The simulation results show that the injection of assist light can increase the phase delay of the output optical signal and enhance the slow light effect. Furthermore, when the assist light optical power is in the range of 0–15 dBm, the slow light effect is strong.

Fiber SPR two-dimensional micro displacement sensor based on the coaxial double waveguide with a conical structure.

Fiber SPR micro displacement sensor cannot be used for two-dimensional displacement sensing at present. In this paper, we proposed and demonstrated a fiber SPR two-dimensional micro displacement sensor based on the coaxial double waveguide with a conical structure. The coaxial double waveguide is fused into a cone as the light injection fiber, and two different forms of outgoing light fields can be obtained through two cores of the fiber. The horn shaped light field emitted by the ring core of the coaxial double waveguide can cooperate with the sensing fiber to realize the micro displacement sensing in the x-axis direction. And the straight beam emitted by the middle core of the coaxial double waveguide can cooperate with the sensing fiber to realize the micro displacement sensing in the y-axis direction. Through simulation analysis and experimental test, its average wavelength sensitivity and light intensity sensitivity of the x-axis displacement are 0.0537nm/µm and 0.000124a.u./µm, respectively. And that of the y-axis displacement are 0.315nm/µm and 0.00277a.u./µm, respectively. The proposed fiber sensor realizes the two-dimensional displacement sensing based on SPR, which can be widely used in the fields of two-dimensional micro displacement measurement and two-dimensional position precision positioning.

Sensitivity enhancement of a dispersive cavity with squeezed vacuum light injection

The measurement sensitivity of a cavity could be enhanced for sensing applications in an anomalous dispersion condition. In this paper, we find that when injecting a squeezed vacuum light into a dispersive cavity, the sensitivity could be improved further, even beating the standard quantum limit at the detuning frequencies via controlling the dispersion condition. It is amazing that normal dispersion is superior to anomalous dispersion in improving the measurement sensitivity in the presence of a squeezed vacuum field. It implies this paper could be used to realize high-precision sensing applications.

Intravitreal injection of mitochondrial DNA induces cell damage and retinal dysfunction in rats

BackgroundRetinal neurodegeneration is induced by a variety of environmental insults and stresses, but the exact mechanisms are unclear. In the present study, we explored the involvement of cytosolic mitochondrial DNA (mtDNA), resulting in the cGAS-STING dependent inflammatory response and apoptosis in retinal damage in vivo.MethodsRetinal injury was induced with white light or intravitreal injection of lipopolysaccharide (LPS). After light- or LPS-induced injury, the amount of cytosolic mtDNA in the retina was detected by PCR. The mtDNA was isolated and used to transfect retinas in vivo. WB and real-time PCR were used to evaluate the activation of cGAS-STING pathway and the levels of apoptosis-associated protein at different times after mtDNA injection. Retinal cell apoptosis rate was detected by TUNEL staining. Full-field electroretinography (ERG) was used to assess the retinal function.ResultsLight injury and the intravitreal injection of LPS both caused the leakage of mtDNA into the cytoplasm in retinal tissue. After the transfection of mtDNA in vivo, the levels of cGAS, STING, and IFN-β mRNAs and the protein levels of STING, phosph-TBK1, phospho-IRF3, and IFN-β were upregulated. mtDNA injection also induced the activation of caspase 3 and caspase 9. BAX and BAK were increased at both the mRNA and protein levels. The release of cytochrome c from the mitochondria to the cytosol was increased after mtDNA injection. The wave amplitudes on ERG decreased and retinal cell apoptosis was detected after mtDNA injection.ConclusionsCytosolic mtDNA triggers an inflammatory response. It also promotes apoptosis and the dysfunction of the retina.

Enhancement of power conversion efficiency by chlorophyll and carotenoid co-sensitization in the biosolar cells

Photosynthetic pigment-based biosolar cells (BSCs) have attracted much attention over the past few years in the field of artificial photosynthesis. To further improve the power conversion efficiency (PCE) of chlorophyll (Chl)-based bilayer BSCs, co-sensitization effects of three carboxylated chromophores, methyl trans-32-carboxy-pyropheophorbide-a (H2Chl-1), methyl 7-deformyl-7-(trans-carboxyethenyl)-pyropheophorbide-b (H2Chl-2), and β-apo-8′-carotenoic acid (Car) were investigated as H2Chl-1:H2Chl-2, H2Chl-1:Car, and H2Chl-2:Car combinations. The homogeneously co-sensitized mesoporous TiO2 (m-TiO2) layer (TiO2–H2Chl:Car) serves as the photoactive and electron extraction layer, while a Chl-a derivative, zinc methyl 3-devinyl-3-hydroxymethyl-pyropheophorbide-a (ZnChl) forms J-type self-aggregation film and acts as electron donor layer. The light absorption and electron injection efficiency of the TiO2 sensitized H2Chl-1:Car blends are better than those of other types of co-sensitization after optimizing the blend ratio of each type. The electron absorption spectrum of TiO2–(H2Chl-1:Car) at the best mass ratio of 10:3 (molar ratio of 12:5) showed wider absorption band in 350–450 nm region compared to the spectrum of sole TiO2–(H2Chl-1). The charge transfer resistance was significantly reduced when TiO2–(H2Chl-1:Car) was applied for BSCs. The best PCE of 2.13% was achieved using TiO2–(H2Chl-1:Car = 10:3), which corresponds to 40% increase of PCE compared to the device using TiO2–(H2Chl-1) without Car.

Realization of High‐Voltage Output on Monolithic Silicon Solar Cells in Series for Self‐Powered Systems

Crystalline silicon solar cells dominate the photovoltaic market nowadays. However, they are rarely used in self‐powered systems (with an operating voltage of 1.5∼12.0 V) mainly because of the low integration of silicon solar cell modules, which need slicing and then series connection. Herein, a series‐interconnected solar cell which can be prepared on a monolithic silicon wafer, with the capability to output high voltage by controlling the number of sub‐cells, is proposed. Further, based on a technology computer aided design (TCAD) numerical simulation, an in‐depth analysis of an unconventional non‐shunt resistance type of leakage mechanism under electric and light injection which has not been reported before is proposed and performed, finding that the leakage current can be divided into three stages that are closely related to the variation in the conductivity (resistance) of the transition region (TR) under injection conditions. Then, several targeted methods especially an unusual method of increasing the recombination to constrain the rise in conductivity in TR are proposed to improve its efficiency by suppressing leakage current at different stages. Finally, simulation reveals that the proposed monolithic on‐chip solar micromodules enable not only high voltage but also high efficiency (≥24.0%), which well meets the requirements of self‐powered systems at low cost.

Design and implementation of a device based on an off-axis parabolic mirror to perform luminescence experiments in a scanning tunneling microscope.

We present the design, implementation, and illustrative results of a light collection/injection strategy based on an off-axis parabolic mirror collector for a low-temperature Scanning Tunneling Microscope (STM). This device allows us to perform STM induced Light Emission (STM-LE) and Cathodoluminescence (STM-CL) experiments and in situ Photoluminescence (PL) and Raman spectroscopy as complementary techniques. Considering the Étendue conservation and using an off-axis parabolic mirror, it is possible to design a light collection and injection system that displays 72% of collection efficiency (considering the hemisphere above the sample surface) while maintaining high spectral resolution and minimizing signal loss. The performance of the STM is tested by atomically resolved images and scanning tunneling spectroscopy results on standard sample surfaces. The capabilities of our system are demonstrated by performing STM-LE on metallic surfaces and two-dimensional semiconducting samples, observing both plasmonic and excitonic emissions. In addition, we carried out in situ PL measurements on semiconducting monolayers and quantum dots and in situ Raman on graphite and hexagonal boron nitride (h-BN) samples. Additionally, STM-CL and PL were obtained on monolayer h-BN gathering luminescence spectra that are typically associated with intragap states related to carbon defects. The results show that the flexible and efficient light injection and collection device based on an off-axis parabolic mirror is a powerful tool to study several types of nanostructures with multiple spectroscopic techniques in correlation with their morphology at the atomic scale and electronic structure.

Amplitude-Modulated Cavity-Enhanced Absorption Spectroscopy with Phase-Sensitive Detection: A New Approach Applied to the Fast and Sensitive Detection of NO2.

Accurate and sensitive measurements of NO2 play an extremely important role in atmospheric studies. Increasingly, studies require NO2 measurements with parts per trillion by volume (pptv-level) detection limits. Other desirable instrument attributes include ease of use, long-term stability, and low maintenance. In this work, we report the development of an amplitude-modulated multimode-diode-laser-based cavity-enhanced absorption spectroscopy (AM-CEAS) system operating at 406 nm that uses phase-sensitive detection for extremely sensitive NO2 detection. The laser was TTL-modulated at 35 kHz. The mirror reflectivity was determined to be 99.985% based on the ring-down time measurement. The cavity base length was 47.5 cm, giving an effective absorption pathlength of ∼3.26 km. AM-CEAS achieved a 1σ detection precision of 35 pptv in a 1 s data acquisition time (4.98 × 10-10 cm-1), over 4 times lower than that attained using a ring-down approach and the same optical system. The AM-CEAS precision improved to 8 pptv over a data acquisition time of 30 s (1.14 × 10-10 cm-1). The AM-CEAS method with the multimode diode laser integrates the advantages of high light injection efficiency like on-axis alignment cavity ring-down spectroscopy, low cavity-mode noise like off-axis alignment CEAS, and narrow-bandwidth high-sensitivity weak signal detection of modulation spectroscopy, providing a powerful, straightforward, and general method for ultrasensitive absorption and extinction measurements.

Light luminescence and trapping in polydimethylsiloxane foils with low concentration of gold nanoparticles

Light trapping and luminescence have been observed in polydimethylsiloxane (PDMS) foils containing about 0.1–0.2 wt% gold nanoparticles (AuNPs). The so-prepared PDMSs have been physically characterized using SEM microscopy, UV–Vis, FTIR and Raman spectroscopies. The used AuNPs have been controlled by means of the surface plasmon resonance absorption spectra. In the AuNPs–PDMS foils, a luminescence peak at about 425 nm has been induced by an exciting light at 280 nm. The light injection with an optical fiber is trapped inside the polymer-containing NPs and illuminates all the polymer volume. The measurements of scattered light show an increment in the light intensity due to the presence of AuNPs and air bubbles inducing diffractions, reflections and Mie scattering. Further investigations have been conducted irradiating the PDMS with AuNPs in vacuum with 2.9 MeV proton beams producing luminescence in the blue region. The mechanisms of light trapping and luminescence and the possible applications of the prepared material are presented and discussed.

Research on optimization of annealing process based on N-type TOPCon solar cell

In recent years, developing new structure and technology has always been an important link in the production and manufacture on photovoltaic cells. Among all high-efficiency crystalline silicon solar cells, the tunnel oxide passivated contact (TOPCon) solar cell has attracted much attention due to its excellent passivation and compatibility with the traditional crystalline silicon solar cells. This article first introduces the basic structure and process route of the tunneling oxide passivation contact (TOPCon) solar cell. Then the annealing process was studied. Experiments on the effects of different annealing temperatures and times on the doping characteristics were carried out, and the experimental results were analyzed. The experimental results show that the annealing temperature and time have a very important effect on the annealing effect of ion implanted silicon. Finally, the light injection annealing process is researched and experimented. Experimental results show that the efficiency of the light injection annealing method is significantly improved, which is mainly manifested in the improvement of Voc (open circuit voltage) and FF (fill factor).