Effect Of Quantum Efficiency Research Articles

Performance analysis and optimization of inverted inorganic CsGeI3 perovskite cells with carbon/copper charge transport materials using SCAPS-1D.

Organic-inorganic perovskite solar cells (PSCs) have achieved the power conversion efficiencies (PCEs) of more than 25%. However, the organic compound in the material is causing structural degradation of the PSC owing to heat (thermal instability), humidity and moisture. This has led to the exploration of only inorganic perovskite materials. Inorganic PSCs such as caesium have seen a breakthrough by achieving highly stable PSC with PCE exceeding 15%. In this work, the inorganic non-toxic PSCof caesium germanium tri-iodide (CsGeI3) is numerically modelled in SCAPS-1D with two carbon-based electron transport layers (ETLs) and two copper-based hole transport layers (HTLs). This study introduces in-depth numerical modelling and analysis of CsGeI3 through continuity and Poisson equations. Cu HTLs are selected to increase the electric conductivity of the cell, while carbon-based ETL is used toincrease the thermal conductivity of the PSC. A total of fourunique PSC structures are designed and presented. A systematic approach is adopted to obtain the optimized PSC design parameters for maximum performance. From the optimized results, it is observed that the C60/CsGeI3/CuSCN structure is the highest performance PSC, with open-circuit voltage (V oc) of 1.0169 V, short-circuit current density (J sc) of 19.653 mA cm-2, fill factor of 88.13% and the PCE of 17.61%. Moreover, the effect of quantum efficiency, electric field, interface recombination, interface defects, layer thickness, defect density, doping concentration, working temperature and reflection coating on the cell performance are studied in detail.

Quantum Efficiency Effects on Modal Gain, Threshold Current and Threshold Current Density of PbSe/Pb0.934Sr0.066 Se Multiple Quantum Well Structure

Quantum Efficiency Effects on Modal Gain, Threshold Current and Threshold Current Density of PbSe/Pb0.934Sr0.066 Se Multiple Quantum Well Structure

Enhanced performance of an S-band fiber laser using a thulium-doped photonic crystal fiber

This work proposes a new method to enhance the performance of an S-band fiber laser by using a thulium-doped photonic crystal fiber (PCF). The proposed method is based on amplified spontaneous emission (ASE) suppression provided by the thulium-doped PCF unique geometric structure. The enhanced performance of this filter based PCF is dependent on the short and long cut-off wavelength characteristics that define the fiber transmission window. Realizing the short wavelength cut-off location requires the PCF cladding to be doped with a high index material, which provides a refractive index difference between the core and cladding region. Achieving the long cut-off wavelength necessitates enlarging the size of the air holes surrounding the rare-earth doped core region. The PCF structure is optimized so as to achieve the desired ASE suppression regions of below 0.8 μm and above 1.8 μm. The laser performance is simulated for different host media, namely pure silica, alumino-silicate, and fluoride-based fiber ZBLAN based on this thulium-doped PCF design. The host media spectroscopic details, including lifetime variations and quantum efficiency effect on the lasing emission are also discussed. Information on the filter based PCF design is gathered via a full-vectorial finite element method analysis and specifically a numerical modelling solution for the energy level rate equation using the Runge–Kutta method. Results are analyzed for gain improvement, lasing cavity, laser efficiency and effect of core size diameter variation. Results are compared with conventional thulium-doped fiber and thulium-doped PCF for every single host media. We observe that the ZBLAN host media is the most promising candidate due to its greater quantum efficiency.

Analysis of dependence of electroluminescence efficiency of AlInGaN LED heterostructures on pumping

AbstractThe work is devoted to explanation of the decrease of external quantum efficiency (QE) with increase of pumping density typically observed for AlInGaN heterostrucures. It is shown as a result of numerical modeling that while the increase of QE at low pumping density is due to the competition between radiative and non‐radiative recombination, the decrease of QE at large pumping density is caused by decrease of injection efficiency for the holes into the active area. A modified LED heterostructure is suggested, for which the effect of QE decreasing is not expected. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Adaptive shaping system for both spatial and temporal profiles of a highly stabilized UV laser light source for a photocathode RF gun

We have been developing a stable and highly qualified ultraviolet (UV) laser pulse as a light source of an RF gun for an injector candidate of future light sources. Our gun cavity is a single-cell pillbox, and the copper inner wall is used as a photocathode. The chirped pulse amplification (CPA) Ti:sapphire laser system is operated at a repetition rate of 10 Hz. At the third harmonic generation (central wavelength—263 nm), the laser pulse energy after a 45 cm silica rod is up to 850 μJ/pulse. In its present status, the laser's pulse energy stability has been improved down to 0.2∼0.3% at the fundamental, and 0.7–1.4% (rms; 10 pps; 33,818 shots) at the third harmonic generation, respectively. This stability has been held for 1 month continuously, 24 h a day. The improvements we had passively implemented were to stabilize the laser system as well as the environmental conditions. We introduced a humidity-control system kept at 50–60% in a clean room to reduce damage to the optics. In addition, we prepared a deformable mirror for spatial shaping and a spatial light modulator based on fused-silica plates for temporal shaping. We are applying both the adaptive optics to automatic optimization of the electron beam bunch to produce lower emittance with the feedback routine. Before the improvements, the electron beam produced from a cathode suffered inhomogeneous distribution caused by the quantum efficiency effect, and some pulse distortions caused by its response time. However, we can now freely form any arbitrary electron beam distribution on the surface of the cathode.

Effect of CCD readout noise in astronomical speckle imaging

A theoretical and experimental comparison of photon-countingcameras and CCD's for use in astronomical speckle imaging wasperformed. Photon-counting cameras able to detect single-photonevents typically exhibit a lower quantum efficiency (QE) and suffersaturation effects at high light levels. In contrast, CCD's offera high QE and virtually unlimited photon-count rate. However CCD'sare limited at lower light levels by noise associated with the readoutprocess. Speckle-imaging performance was quantified by derivationof the signal-to-noise ratio (SNR) of the power spectrum and theKnox-Thompson product to include CCD readout noise. Ground-basedtelescope observations at various light levels were obtained with anadvanced, high-speed, low-noise CCD camera to verify SNRexpressions. The useful operating ranges for these two camera typeswere compared by consideration of the effects of QE, readout noise, andmaximum photon-count rate. Although photon-counting camerascontinued to dominate low-light-level applications, CCD's are shown tooffer significant improvements over photon-counting cameras for a widerange of light levels. Future reductions of readout noise will further improve CCD speckle-imaging performance.