Showing papers in "Optoelectronics Letters in 2015"
TL;DR: In this article, the surface-enhanced Raman scattering (SERS) was used as an analytical tool for the detection and identification of pathogenic bacteria of Escherichia coli (E. coli) and Salmonella typhimurium (S. typhimurus).
Abstract: In this paper, the surface-enhanced Raman scattering (SERS) is used as an analytical tool for the detection and identification of pathogenic bacteria of Escherichia coli (E. coli) and Salmonella typhimurium (S. typhimurium). Compared with normal Raman signal, the intensity of SERS signal is greatly enhanced. After processing all SERS data, the obvious differences between the SERS spectra of two species are determined. And applying the chemometric tools of principal component analysis and hierarchical cluster analysis (PCA-HCA), the SERS spectra of two species are distinguished more accurately. The results indicate that SERS analysis can provide a rapid and sensitive method for the detection of pathogenic bacteria.
30 citations
TL;DR: In this article, an all-fiber sensor based on a cascaded optical fiber device is proposed and demonstrated, and its sensor head is composed of a core-off Mach-Zehnder interferometer (MZI) and a long-period fiber grating (LPFG).
Abstract: An all-fiber sensor based on a cascaded optical fiber device is proposed and demonstrated, and its sensor head is composed of a core-offset Mach-Zehnder interferometer (MZI) and a long-period fiber grating (LPFG). In the experiment, two dips shaped by the intermodulation between the interference fringe of MZI and the resonant wavelength of LPFG are monitored. Experimental results show that temperature sensitivities of two dips are 0.060 7 nm/°C and 0.056 3 pm/°C, and the refractive index (RI) sensitivities are −18.025 nm/RIU and −55.06 nm/RIU, respectively. The simultaneous measurement of the temperature and external RI is demonstrated based on the sensitive matrix. Its low fabrication cost, simple configuration and high sensitivity make this sensor have potential applications in chemical and biological sensing.
24 citations
TL;DR: In this paper, a microring resonator (MRR) system using double-series ring resonators is proposed to generate and investigate the Rabi oscillations, which is made up of silicon-on-insulator and attached to bus waveguide which is used as propagation and oscillation medium.
Abstract: In this paper, a microring resonator (MRR) system using double-series ring resonators is proposed to generate and investigate the Rabi oscillations. The system is made up of silicon-on-insulator and attached to bus waveguide which is used as propagation and oscillation medium. The scattering matrix method is employed to determine the output signal intensity which acts as the input source between two-level Rabi oscillation states, where the increase of Rabi oscillation frequency with time is obtained at the resonant state. The population probability of the excited state is higher and unstable at the optical resonant state due to the nonlinear spontaneous emission process. The enhanced spontaneous emission can be managed by the atom (photon) excitation, which can be useful for atomic related sensors and single-photon source applications.
17 citations
TL;DR: In this paper, a novel fiber Bragg grating (FBG) displacement sensor is proposed, which can achieve wide measuring range displacement detection with variable measurement precision due to its mechanical transfer structure of helical bevel gear.
Abstract: A novel fiber Bragg grating (FBG) displacement sensor is proposed, which can achieve wide measuring range displacement detection with variable measurement precision due to its mechanical transfer structure of helical bevel gear A prototype is designed and fabricated The maximum detection displacement of this prototype is 1751 m, and the precision grade changes from 02% to 67% Through analyzing the experiment data which is obtained in the calibration experiment, the measuring range of this sensor is from 0 m to 1532 m, and the wavelength shift errors between experiment data and theory calculation are all less than 5%
15 citations
TL;DR: In this article, a compact optical fiber sensor based on a Mach-Zehnder interferometer (MZI) cascaded with fiber Bragg grating (FBG) for simultaneous measurement of refractive index (RI) and temperature is presented.
Abstract: In this paper, we propose and experimentally demonstrate a compact optical fiber sensor based on a Mach-Zehnder interferometer (MZI) cascaded with fiber Bragg grating (FBG) for simultaneous measurement of refractive index (RI) and temperature. In order to get a proper spectrum, we discuss the effects of different structure parameters of MZI. Using the resonant wavelength of the FBG (DipFBG) and the interference dip of the MZI (Dip1), the RI and temperature of the surrounding medium can be determined. The sensor has good operation linearity. The experimental results show that the distinctive spectral sensitivities are 0.071 75 nm/°C and −91.766 67 nm/RIU (refraction index unit) for Dip1 and 0.009 09 nm/°C for DipFBG.
10 citations
TL;DR: In this article, a detailed theoretical and numerical study on double-phase-shifted fiber Bragg grating (FBG) is performed based on the transfer matrix method, which shows that very different temporal pulse waveforms can be achieved by adjusting the length ratio (α=L 2/L 1).
Abstract: Based on the transfer matrix method, a detailed theoretical and numerical study on double-phase-shifted fiber Bragg grating (FBG) is investigated. Temporal responses of the double-phase-shifted FBG to optical pulse are analyzed and the influence of the two phase-shifts’ position on the reflected output pulse is evaluated. Results demonstrate that very different temporal pulse waveforms can be achieved by adjusting the length ratio (α=L 2/L 1). Specifically, a transform-limited Gaussian input optical pulse can be shaped into flat-top square pulse (α=1.81) or two identical optical pulse sequences (α=1.93).
9 citations
TL;DR: In this article, the space diversity reception of the binary phase-shift keying (BPSK) modulated free space optical (FSO) system over Malaga (M) fading channels is investigated in detail.
Abstract: Based on the space diversity reception, the binary phase-shift keying (BPSK) modulated free space optical (FSO) system over Malaga (M) fading channels is investigated in detail. Under independently and identically distributed and independently and non-identically distributed dual branches, the analytical average bit error rate (ABER) expressions in terms of H-Fox function for maximal ratio combining (MRC) and equal gain combining (EGC) diversity techniques are derived, respectively, by transforming the modified Bessel function of the second kind into the integral form of Meijer G-function. Monte Carlo (MC) simulation is also provided to verify the accuracy of the presented models.
9 citations
TL;DR: In this article, the photocatalytic properties of AgAu-TiO2 NPs were investigated on the photodecomposition of methylene blue (MB).
Abstract: In this paper, for improving the photocatalytic efficiency of titania (TiO2) nanoparticles (NPs), AgAu alloy-TiO2 core-shell NPs are fabricated via a sol-gel (SG) process in the presence of AgAu alloy NPs with block copolymer shells as templates. The photocatalytic activities of the AgAu-TiO2 NPs on the photodecomposition of methylene blue (MB) are investigated. The AgAu-TiO2 composite NPs coated with 5.0% titania related to block copolymers show higher photocatalytic activity than the other samples in which the titania contents are larger than 5.0%. The results indicate that the increase of the thickness of the TiO2 shell leads to the decrease of the photocatalytic activity.
9 citations
TL;DR: In this article, a modal interferometer is fabricated by splicing a section of photonic crystal fiber (PCF) with a single-mode fiber (SMF), and the air holes of the PCF are fully collapsed by the discharge arc during the splicing procedure.
Abstract: A novel miniature Fabry-Perot interferometric (FPI) temperature sensor is proposed and demonstrated experimentally. The modal interferometer is fabricated by just splicing a section of photonic crystal fiber (PCF) with a single-mode fiber (SMF). The air holes of the PCF are fully collapsed by the discharge arc during the splicing procedure to enhance the reflection coefficient of the splicing point. The transmission spectra with different temperatures are measured, and the experimental results show that the linear response of 11.12 pm/°C in the range of 30–80 °C is obtained. This sensor has potential applications in temperature measurement field.
8 citations
TL;DR: In this paper, a communication system based on an ultraviolet (UV) laser at 266 nm is presented to improve the communication distance, and the pulse frequency-shift keying (FSK) modulation scheme is studied and improved in order to reduce the bit error rate (BER) on a field programmable gate array (FPGA).
Abstract: A communication system based on an ultraviolet (UV) laser at 266 nm is presented to improve the communication distance. The pulse frequency-shift keying (FSK) modulation scheme is studied and improved in order to reduce the bit error rate (BER), and is put into practice on a field programmable gate array (FPGA). The mathematical models of the modulation and demodulation are established. A test platform is set up to measure the energy density and pulse response under different distances and receiver elevation angles. It is shown that the omnibearing communication can be realized, and the bit rate is limited to 12.5 Mbit/s. The BER is estimated to be less than 10−7 at distance of 300 m in line-of-sight (LOS) communication model and to be less than 10−6 at distance of 80 m in non-line-of-sight (NLOS) communication model.
8 citations
TL;DR: In this paper, a microwave photonic link (MPL) with high spurious-free dynamic range (SFDR) is proposed and analyzed, where the optical carrier is divided equally into two paths.
Abstract: A microwave photonic link (MPL) with high spurious-free dynamic range (SFDR) is proposed and analyzed. The optical carrier is divided equally into two paths. The path 1 is modulated by radio frequency (RF) signals in a Mach-Zehnder modulator (MZM), and the phase of path 2 is controlled before the combination with path 1. By properly adjusting the phase difference of the two paths with the optical phase shifter, the third-order intermodulation distortion (IMD3) can be significantly suppressed. A proof-of-concept simulation is carried out. The results show that a reduction of 40 dB in the IMD3 and an improvement of 21.1 dB in the SFDR are achieved as compared with the conventional MZM-based MPL. The proposed MPL shows the advantages of simple structure, low cost and high efficiency.
TL;DR: Experimental results show that this method can efficiently and fast segment the tumors from complex lung CT images with higher accuracy.
Abstract: In lung CT images, the edge of a tumor is frequently fuzzy because of the complex relationship between tumors and tissues, especially in cases that the tumor adheres to the chest and lung in the pathology area. This makes the tumor segmentation more difficult. In order to segment tumors in lung CT images accurately, a method based on support vector machine (SVM) and improved level set model is proposed. Firstly, the image is divided into several block units; then the texture, gray and shape features of each block are extracted to construct eigenvector and then the SVM classifier is trained to detect suspicious lung lesion areas; finally, the suspicious edge is extracted as the initial contour after optimizing lesion areas, and the complete tumor segmentation can be obtained by level set model modified with morphological gradient. Experimental results show that this method can efficiently and fast segment the tumors from complex lung CT images with higher accuracy.
TL;DR: In this paper, the fabrication and optical properties of sub-micrometer-thick Ge20Sb15Se65 chalcogenide rib waveguides are reported.
Abstract: We report the fabrication and optical properties of sub-micrometer-thick Ge20Sb15Se65 chalcogenide rib waveguides. The radio-frequency (RF) magnetron sputtering method is used to deposit 0.83 μm-thick films. A protective layer of SU-8 is employed to prevent the attack of the alkaline developer, and CHF3 is used as the etching plasma for reactive ion etching (RIE). Finally, the resulted rib waveguides with smooth sidewalls and vertical pattern profiles are rendered. The propagation losses for 4 μm-wide waveguides are measured to be 0.7 dB/cm for transverse electric (TE) modes and 0.68 dB/cm for transverse magnetic (TM) modes at 1 550 nm via the cutback method.
TL;DR: In this paper, a diamond-type Ag nano-antenna arrays are proposed for increasing the efficiency of solar cells by localized surface plasmons resonance (LSPR), which is theoretically investigated by the finite difference time domain (FDTD) method.
Abstract: The optical metal nanoantenna on thin film solar cell is effective to enhance light absorption. In this paper, the diamond-type Ag nanoantenna arrays are proposed for increasing the efficiency of solar cells by localized surface plasmons resonance (LSPR). The effect of metal nanoantenna on the absorption enhancement is theoretically investigated by the finite difference time domain (FDTD) method. Broadband absorption enhancements in both visible and near-infrared regions are demonstrated in case of solar cell with diamond-type Ag nanoantennas. The spectral response is manipulated by geometrical parameters of the nanoantennas. The maximum enhancement factor of 1.51 for solar cell is obtained. For comparison, the other three nanoantennas are also analyzed. The results show that the solar cell with optimized diamond-type nanoantenna arrays is more efficient in optical absorption.
TL;DR: In this paper, a series of Ce3+, Eu2+ and Ce3+-Eu 2+ doped Ca9Al(PO4)7 phosphors are synthesized by a high temperature solid-state method.
Abstract: A series of Ce3+, Eu2+ and Ce3+-Eu2+ doped Ca9Al(PO4)7 phosphors are synthesized by a high temperature solid-state method. Under 291 nm excitation, Ca9Al(PO4)7:Ce3+ has one emission band at 356 nm, which is attributed to 4f05d1→4f1 transition of Ce3+. Under 305 nm excitation, Ca9Al(PO4)7:Eu2+ presents one emission band at 445 nm, which is assigned to 4f65d1→4f7 transition of Eu2+. Energy transfer from Ce3+ to Eu2+ in Ca9Al(PO4)7 is validated and proved to be a resonant type via a quadrupole-quadrupole interaction. Critical distance (Rc) of Ce3+ to Eu2+ in Ca9Al(PO4)7 is calculated to be 1.264 nm. Moreover, the emission intensity of Ca9Al(PO4)7:Ce3+, Eu2+ can be tuned by properly adjusting the relative doping composition of Ce3+/Eu2+.
TL;DR: In this article, an optical fiber Fabry-Perot (FP) interferometric sensor is used to detect partial discharge from electrode discharge, which is fabricated by photolithography.
Abstract: In this paper, a partial discharge detection system is proposed using an optical fiber Fabry-Perot (FP) interferometric sensor, which is fabricated by photolithography. SU-8 photoresist is employed due to its low Young’s modulus and potentially high sensitivity for ultrasound detection. The FP cavity is formed by coating the fiber end face with two layers of SU-8 so that the cavity can be controlled by the thickness of the middle layer of SU-8. Static pressure measurement experiments are done to estimate the sensing performance. The results show that the SU-8 based sensor has a sensitivity of 154.8 nm/kPa, which is much higher than that of silica based sensor under the same condition. Moreover, the sensor is demonstrated successfully to detect ultrasound from electrode discharge.
TL;DR: In this paper, a terahertz (THz) filter based on metamaterial consisting of the periodical double symmetric splits ring resonator (DS-SRR) array is presented.
Abstract: In this paper, we present the design, simulation, fabrication and characterization of a terahertz (THz) filter based on metamaterial consisting of the periodical double symmetric splits ring resonator (DS-SRR) array. We can observe that the metamaterial-based filter possesses a band-pass transmission when the electrical field is along y direction, and it possesses a low-pass transmission when the electrical field is along x direction. Our results demonstrate that the proposed filter can realize the switching between band-pass effect and low-pass effect by only changing the polarization direction of the incident electromagnetic wave. Moreover, the calculated surface current distributions are also used to analyze the switchable mechanism of the THz metamatrial filter. Therefore, the proposed THz wave filter has a potential application in THz wave communication systems.
TL;DR: In this paper, a dual-wavelength fiber Bragg grating (FBG) laser based on a distributed feedback (DFB) laser injection is proposed and experimentally demonstrated.
Abstract: A tunable dual-wavelength fiber Bragg grating (FBG) laser based on a distributed feedback (DFB) laser injection is proposed and experimentally demonstrated. The wavelength spacing can be tuned by adjusting the operation temperature of the DFB laser. When the DFB works at 25 °C, a dual-wavelength simultaneous oscillation at 1 549.67 nm and 1 553.44 nm with wavelength spacing of 3.77 nm is achieved. Our experimental results demonstrate the new concept of dual-wavelength lasing with a DFB laser injection and the technical feasibility.
TL;DR: In this article, a thermally tunable terahertz metamaterial absorber with InSb embedded in a metal-dielectric-metal structure is proposed, which can be dynamically tuned from 0.82 THz to 1.02 THz.
Abstract: A thermally tunable terahertz metamaterial absorber (MA) with InSb embedded in a metal-dielectric-metal structure is proposed. The transmission and tuning properties of the proposed metamaterial absorber are analyzed for the temperature ranging from 160 K to 350 K. The simulated results show that the maximum absorption of the absorber is nearly 99.8% at a full-width at half-maximum (FWHM) of 38 GHz, and the absorption frequency can be dynamically tuned from 0.82 THz to 1.02 THz.
TL;DR: In this article, the silver nanowire arrays with regular and uniform size were successfully fabricated inside the nanochannels of anodic aluminum oxide (AAO) template by a simple paired cell method.
Abstract: The silver (Ag) nanowire arrays with regular and uniform size were successfully fabricated inside the nanochannels of anodic aluminum oxide (AAO) template by a simple paired cell method. X-ray diffraction (XRD) and scanning electron microscopy (SEM) results indicate that the as-synthesized samples are composed of face-centered cubic structure, and the average diameter is about 60–70 nm. Transmission electron microscopy (TEM) and the corresponding fast Fourier transformation (FFT) results show that Ag nanowires have a preferred single-crystal structure. Ultraviolet- visible (UV-vis) spectrum of Ag nanowire arrays exhibits UV emission band at 383 nm which can be attributed to the transverse dipole resonance of Ag nanowire arrays. A good surface-enhanced Raman scattering (SERS) spectrum is observed by excitation with a 514.5 nm laser, and the intensity of the SERS peak is about 23 times higher than that of the normal Raman peak measured from an empty AAO template. The high enhancement factor suggests that this method can be used to fabricate SERS sensor with high efficiency.
TL;DR: Aiming at the low speed of traditional scale-invariant feature transform (SIFT) matching algorithm, an improved matching algorithm is proposed in this paper, and results show that the matching time is reduced by 73.3% and the matching points are entirely correct.
Abstract: Aiming at the low speed of traditional scale-invariant feature transform (SIFT) matching algorithm, an improved matching algorithm is proposed in this paper. Firstly, feature points are detected and the speed of feature points matching is improved by adding epipolar constraint; then according to the matching feature points, the homography matrix is obtained by the least square method; finally, according to the homography matrix, the points in the left image can be mapped into the right image, and if the distance between the mapping point and the matching point in the right image is smaller than the threshold value, the pair of matching points is retained, otherwise discarded. Experimental results show that with the improved matching algorithm, the matching time is reduced by 73.3% and the matching points are entirely correct. In addition, the improved method is robust to rotation and translation.
TL;DR: A novel two-stage enhanced-iterative-algorithm PTS (TS-EIA-PTS) PAPR reduction algorithm with lower computational complexity is proposed, and with the increase of the subcarrier number, the computational complexity can be further reduced.
Abstract: Because the partial transmit sequence (PTS) peak-to-average power ratio (PAPR) reduction technology for optical orthogonal frequency division multiplexing (O-OFDM) systems has higher computational complexity, a novel two-stage enhanced-iterative-algorithm PTS (TS-EIA-PTS) PAPR reduction algorithm with lower computational complexity is proposed in this paper. The simulation results show that the proposed TS-EIA-PTS PAPR reduction algorithm can reduce the computational complexity by 18.47% in the condition of the original signal sequence partitioned into 4 sub-blocks at the remaining stage of n-d=5. Furthermore, it has almost the same PAPR reduction performance and the same bit error rate (BER) performance as the EIA-PTS algorithm, and with the increase of the subcarrier number, the computational complexity can be further reduced. As a result, the proposed TS-EIA-PTS PAPR reduction algorithm is more suitable for the practical O-OFDM systems.
TL;DR: In this paper, the synthesis and photoluminescence characteristics of two new phosphors Pr3+: CaYAlO4 (CYA) and PR3+/Tb3++: CYA for light emitting diodes (LEDs) are investigated.
Abstract: In this work, the synthesis and photoluminescence characteristics of two new phosphors Pr3+: CaYAlO4 (CYA) and Pr3+/Tb3+: CYA for light emitting diodes (LEDs) are investigated. 0.5% (atom percentage) Pr3+: CYA exhibits the largest bright yellow emission by varying the Pr3+ concentration, owing to the cross-relaxation process of 3P0+3H4 → 1G4+1G4. The energy level diagram in Pr3+: CYA, especially the positions of 4f5d level and 1S0 level, is discussed. By co-doping Tb3+ ions, the color coordinates of Pr3+/Tb3+: CYA phosphor can be tuned from yellow to white region. Finally, the strongest luminescence emission with color coordinates of (0.339, 0.364) located in the white region can be obtained in 0.3%Tb3+/0.5%Pr3+: CYA phosphor.
TL;DR: Considering the optical attenuation of ocean water, the performance of quantum key distribution (QKD) based on air-water channel is studied in this article, where the authors analyzed the effects of photons' various incident angles to airwater interface on quantum bit error rate (QBER) and the maximum secure transmission distance.
Abstract: Considering the air-water interface and ocean water’s optical attenuation, the performance of quantum key distribution (QKD) based on air-water channel is studied. The effects of photons’ various incident angles to air-water interface on quantum bit error rate (QBER) and the maximum secure transmission distance are analyzed. Taking the optical attenuation of ocean water into account, the performance bounds of QKD in different types of ocean water are discussed. The simulation results show that the maximum secure transmission distance of QKD gradually reduces as the incident angle from air to ocean water increases. In the clearest ocean water with the lowest attenuation, the maximum secure transmission distance of photons far exceeds the the working depth of underwater vehicles. In intermediate and murky ocean waters with higher attenuation, the secure transmission distance shortens, but the underwater vehicle can deploy other accessorial methods for QKD with perfect security. So the implementation of OKD between the satellite and the underwater vehicle is feasible.
TL;DR: In this paper, a switchable dual-wavelength erbium-doped fiber laser (EDFL) with tunable wavelength is demonstrated, which consists of two branches with a fiber Bragg grating (FBG) and a spherical shape structure as fiber filters, respectively.
Abstract: A switchable dual-wavelength erbium-doped fiber laser (EDFL) with tunable wavelength is demonstrated. The ring cavity consists of two branches with a fiber Bragg grating (FBG) and a spherical-shape structure as fiber filters, respectively. By adjusting the variable optical attenuator (VOA), the laser can be switched between the single-wavelength mode and the dual-wavelength mode. The spherical-shape structure has good sensitivity to the temperature. When the temperature changes from 30 °C to 190 °C, the central wavelength of the EDFL generated by the branch of spherical-shape structure varies from 1 551.6 nm to 1 561.8 nm, which means that the wavelength interval is tunable.
TL;DR: The bulb image dimension measurement based on vision (BIDMV) is proposed and a non-contact real-time measurement system of the lamp’s dimension is developed.
Abstract: In order to realize the online measurement of lamp dimension, the bulb image dimension measurement based on vision (BIDMV) is proposed. The image of lamp is obtained by camera. After image processing, such as Otsu algorithm, median filter, ellipse fitting and envelope rectangle fitting, the dimension of lamp can be calculated. Based on this method, a non-contact real-time measurement system of the lamp’s dimension is developed. The precision of the proposed method is 0.07 mm, and it can satisfy the tolerance of the National Standard GB15766.1-2008. The experiment results show that the proposed method has a faster measuring speed and a higher precision compared with other measurement methods.
TL;DR: In this article, a temperature sensor based on the splicing of a core offset multi-mode fiber with two single mode fibers is proposed and demonstrated experimentally, and the temperature sensing principle is analyzed and related experiment is performed.
Abstract: In this paper, a temperature sensor based on the splicing of a core offset multi-mode fiber with two single mode fibers is proposed and demonstrated experimentally. The temperature sensing principle is analyzed and related experiment is performed. By controlling the core offset and splicing length of the specialty multi-mode fiber (SMMF), two sensors with different temperature sensing properties are obtained, and experimental results show that the temperature sensitivity can be up to 48.76 pm/°C in the range of 25—95 °C. Moreover, it has many advantages, including small size, high sensitivity, and simple structure. So it can be used in potential temperature sensing applications, such as industrial production, biomedical science, power electronics, and so on.
TL;DR: In this article, the ternary rare earth complex of Eu(UVA)3Phen is synthesized, and it is characterized by elemental analysis, mass spectra (MS) and infrared (IR) and ultraviolet (UV) spectroscopy.
Abstract: By introducing 2-hydroxy-4-methoxy-benzophenone (UVA) and 1,10-phenanthroline (Phen) as the ligands, the ternary rare earth complex of Eu(UVA)3Phen is synthesized, and it is characterized by elemental analysis, mass spectra (MS) and infrared (IR) and ultraviolet (UV) spectroscopy. Results show that the Eu(III) in complex emits strong red luminescence when it is excited by UV light, and it has higher sensitized luminescent efficiency and longer lifetime. The organic-inorganic thin film of complex Eu(UVA)3Phen doped with nano-TiO2 is prepared, and the nano-TiO2 is used in the luminescence layer to change the luminescence property of Eu(UVA)3Phen. It is found that there is an efficient energy transfer process between ligands and metal ions. Moreover, in an indium tin oxide (ITO)/poly(N-vinylcar-bazole) (PVK)/Eu(UVA)3Phen/Al device, Eu3+ can be excited by intramolecular ligand-to-metal energy transfer process. The main peak of emission at 613 nm is attributed to 5D0→7F2 transition of the Eu3+, and this process results in the enhanced red emission.
TL;DR: In this article, the al-doped ZnO (AZO) buffer layer was used as an electron transport and hole blocking buffer layer in inverted organic solar cells (IOSCs).
Abstract: Al-doped ZnO (AZO) has been used as an electron transport and hole blocking buffer layer in inverted organic solar cells (IOSCs). In this paper, the AZO morphology, optical and structural properties and IOSCs performance are investigated as a function of precursor solution concentration from 0.1 mol/L to 1.0 mol/L. We demonstrate that the device with 0.1 mol/L precursor concentration of AZO buffer layers enhances the short-circuit current and the fill factor of IOSCs simultaneously. The resulting device shows that the power conversion efficiency is improved by 35.6% relative to that of the 1.0 mol/L device, due to the improved surface morphology and transmittance (300–400 nm) of AZO buffer layer.
TL;DR: In this paper, the authors showed that GaN-based MQW photovoltaic devices with five different Mg-doping concentrations of 0 cm−3, 5×1017 cm−2, 2×1018 cm−1, 4×101 8 cm−4, 4 ×1018cm−3 and 7×1016 cm−5 can lead to different hole concentrations in MQWs.
Abstract: A major challenge in GaN based solar cell design is the lack of holes compared with electrons in the multiple quantum wells (MQWs). We find that GaN based MQW photovoltaic devices with five different Mg-doping concentrations of 0 cm−3, 5×1017 cm−3, 2×1018 cm−3, 4×1018 cm−3 and 7×1018 cm−3 in GaN barriers can lead to different hole concentrations in quantum wells (QWs). However, when the Mg-doping concentration is over 1×1018 cm−3, the crystal quality degrades, which results in the reduction of the external quantum efficiency (EQE), short circuit current density and open circuit voltage. As a result, the sample with a slight Mg-doping concentration of 5×1017 cm−3 exhibits the highest conversion efficiency.