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Improved photovoltaic performance of graphene-based solar cells on textured silicon substrate
摘要： Graphene has attracted much interest as an active layer in heterojunction solar cells due to its outstanding properties such as flexibility, transparency, mechanical strength and elevated carrier mobility. In this research, a new technique was presented in order to enhance the efficiency of graphene–based heterojunction solar cells by employing a textured silicon (Si) substrate. Here, two sets of devices were fabricated based on flat and pyramidal structure of Si and the photovoltaic properties of graphene/Si heterojunction solar cells were compared. Selective chemical dissolution of Si wafers was carried out in order to produce pyramidal skeleton. Reduced graphene oxide (rGO) was then transferred on pyramidal Si through electrophoretic deposition (EPD) technique. The evidence of graphene layers on Si substrates was studied using Raman spectroscopy, X–ray diffractometry (XRD) and atomic force microscopy (AFM) analysis. The morphology of samples indicated an enhancement in rGO/Si interface area when the pyramidal structure is applied. Moreover, the enhanced surface area of this sample which is due to elevated roughness of pyramidal structure and wrinkles of graphene layers promotes its antireflective behavior which was proven using reflectance spectroscopy. The average reflectance of the graphene layer on the textured Si was ~14% in the wavelength range of 400–800 nm which is lower than that of rGO on flat Si. The improved optical properties of graphene on pyramidal silicon can broaden its potential applications in optoelectrical devices such as high-efficiency solar cells. In order to study the photovoltaic properties of rGO/Si samples, a passive layer was formed on Si substrate and a square frame of Ag was coated on it which was acted as a top contact. The current–voltage characteristics showed that the efficiency of rGO/Si heterojunction solar cells was improved when textured silicon was applied.
关键词： Schottky junction solar cell,Heterojunctions,Thin films,Reduced graphene oxide,Silicon pyramids,Electrophoretic deposition
更新于2025-09-23 15:19:57
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Improving open-circuit voltage by a chlorinated polymer donor endows binary organic solar cells efficiencies over 17%
摘要： Power conversion efficiency (PCE) of single-junction polymer solar cells (PSCs) has made a remarkable breakthrough recently. Plenty of work was reported to achieve PCEs higher than 16% derived from the PM6:Y6 binary system. To further increase the PCEs of binary OSCs incorporating small molecular acceptor (SMA) Y6, we substituted PM6 with PM7 due to the deeper highest occupied molecular orbital (HOMO) of PM7. Consequently, the PM7:Y6 has achieved PCEs as high as 17.0% by the hot-cast method, due to the improved open-circuit voltage (VOC). Compared with PM6, the lower HOMO of PM7 increases the gap between ELUMO-donor and EHOMO-acceptor, which is proportional to VOC. This research provides a high PCE for single-junction binary PSCs, which is meaningful for device fabrication related to PM7 and commercialization of PSCs.
关键词： binary system,power conversion efficiencies,open-circuit voltage,single junction
更新于2025-09-23 15:19:57
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Diluted nitride type-II superlattices: Overcoming the difficulties of bulk GaAsSbN in solar cells
摘要： We demonstrate type-II GaAsSb/GaAsN superlattices (SL) as a suitable structure to form the lattice-matched 1.0–1.15 eV subcell that would allow the implementation of the optimum monolithic multi-junction solar cell design. The separation of Sb and N atoms during growth leads to an improved composition homogeneity and a lower defect density than in the bulk GaAsSbN counterparts. The type-II band alignment SLs provide long radiative lifetimes that facilitate carrier collection as compared to equivalent type-I SLs. Moreover, the radiative lifetime can be controllably tuned through the period thickness, which is not possible in type-I SLs. A reduced period thickness results in enhanced absorption due to increased wavefunction overlap, as well as in a change in the transport regime from diffusive to quasiballistic, providing improved carrier extraction efficiency. As a result, the short period SL single-junction solar cells show an enhanced power conversion efficiency of 134% over the equivalent bulk devices.
关键词： Strain-balanced,GaAsSbN,Type-II band Alignment,Multi-junction solar cells,Superlattices,1 eV bandgap
更新于2025-09-23 15:19:57
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High responsivity ZnO based p-n homojunction UV-photodetector with series Schottky Barrier
摘要： In the present article, we proposed a p-n homojunction photodetector with a series Schottky barrier and a high value of responsivity in the ultraviolet region. The thin-film photodetector makes use of a junction between an RF-sputtered n-type ZnO nanostructure and a p-type CZO thin film derived through the spin coating process on an ITO coated glass substrate. Palladium metal contacts have been deposited to form the Schottky barrier in series with p-n homojunction. The device has been simulated, fabricated, and tested only after ensuring the stability of the p-type CZO thin film. The measured I-V characteristics of fabricated photodetector under illuminated and dark conditions showed excellent UV response and good rectification property. The device exhibits a peak responsivity of 13.2 A/W for a reverse biasing voltage of 3 V. This value is much above the values reported by others for ZnO based photodetector.
关键词： CZO,photodiode,U-V illumination,ZnO,Schottky junction
更新于2025-09-23 15:19:57
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Laser Annealing Enhanced the Photophysical Performance of Pt/n-PSi/ZnO/Pt-Based Photodetectors
摘要： Herein, the effect of pulsed Nd:YAG laser irradiation at different fluencies in air at room temperature on the performance of n-PSi/ZnO-based UV MSM photodetector was demonstrated. Thermal and photon energies were coupled to synthesize n-PSi/ZnO NCs heterojunctions. The porous silicon (PSi) films with nano-sized pore arrays were first prepared via photoelectrochemical etching (PECE) of n-type silicon wafers with 45 mA/cm2 current density for a duration of 30 min. This was followed by radio frequency sputtering (RFS) of ZnO on PSi at 700 oC and irradiating with a Nd: YAG laser pulses with laser fluence of 40 mJ/cm2. X-ray diffraction analysis indicates the formation of ZnO wurtzite hexagonal crystal structure of n-PSi/ZnO NCs, where the crystallite size decreases (96-29 nm) with number of pulses. Field emission electron scanning microscopy and atomic force microscopy reveal porous nanostructure, arrays of nearly spherically shape particles homogeneously distributed on the entire surface where roughness increases (84-139 nm) with number of pulses. Photoluminescence spectroscopy reveals intrinsic band-to-band transition, donor-acceptor pair emission and quenching of the broadband intensity related to improved of crystallinity, meanwhile the band gap energy of the n-PSi/ZnO NCs is found to decrease (3.26 – 3.13 V). The Nd:YAG laser annealing demonstrate a positive effect on the properties of n-PSi/ZnO NCs photodetector, exhibiting very high sensitivity (3772.92) and very short rise and recovery times (0.30 s and 0.26 s).
关键词： Porous silicon,n-PSi/ZnO junction,Nd-YAG laser,photodetectors
更新于2025-09-23 15:19:57
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Gate Tunable Symmetric Bipolar Junction Transistor Fabricated via Femtosecond Laser Processing
摘要： Two-dimensional (2D) bipolar junction transistor (BJT) with van der Waals heterostructures plays an important role in the development of future nanoelectronics. Herein, a convenient method is introduced for fabricating a symmetric bipolar junction transistor (SBJT) constructed with black phosphorus and MoS2 with femtosecond laser processing. This SBJT exhibits good bidirectional current amplification thanks to its symmetric structure. Next, we place a top gate on one side of the SBJT to change the difference in the major carrier concentration between the emitter and collector in order to further investigate the effect of electrostatic doping on the device’s performance. The SBJT can also act as a gate tunable phototransistor with good photodetectivity and photocurrent gain of β ~ 21. Scanning photocurrent images are used to determine the mechanism governing photocurrent amplification in the phototransistor. These results promote the development of the applications of multifunctional nanoelectronics based on 2D materials.
关键词： Femtosecond laser processing,Phototransistor,Two-dimensional materials,Bipolar junction transistor,Gate tunable
更新于2025-09-23 15:19:57
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[IEEE 2018 15th IEEE India Council International Conference (INDICON) - Coimbatore, India (2018.12.16-2018.12.18)] 2018 15th IEEE India Council International Conference (INDICON) - Influence of the Compositional Variation of Zn <sub/>x</sub> Cd <sub/>1a??x</sub> S (0 a?¤ x a?¤ 0.45) Buffer on Efficiency of Cu <sub/>2</sub> ZnSnSe <sub/>4</sub> Solar Cell: A Simulation
摘要： This paper investigates the manufacturability-aware process of p-n junction formation for photovoltaic cells involving with Si nanoparticle layer. The furnace-based dopant diffusion process of forming a p-n junction consumes a substantial amount of energy. In addition, repetitive production steps prevent the possibility of Si ink-based cells integrating onto ?exible substrates. This research examined the local heating dopant diffusion process by using a ?ber laser at a wavelength of 1064 nm. The infrared beam is delivered onto the wafer stack with a nanoparticle carbon layer and n-type Si ink layer on p-type Si substrates. The nanoparticle carbon ?lm absorbs infrared beam energy and converts photon energy as a thermal source to diffuse the n-type dopant in Si ink into the p-type Si wafer. The Si ink in this paper contains a mixture of Si nanoparticles and an n-type spin-on dopant solution. The TEM results show that Si nanoparticles are uniformly dispersed on the Si wafer surface. This research investigated sheet resistance as a function of laser parameters, including laser power, scanning speed, and pulse frequency for the samples coated with Si ink. Secondary ion mass spectroscopy measurements indicate the presence of an n-type dopant in p-type substrates, with an approximate diffusion depth of 100 nm. The results indicate that the proposed infrared laser treatment technique is promising for the formation of p-n junctions with Si ink-based photovoltaic cells.
关键词： silicon ink,spin-on dopant (SOD),silicon nanoparticle,carbon nanoparticle,?ber laser,Flexible photovoltaic cell,pn junction
更新于2025-09-23 15:19:57
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Improving Radiation Resistance of GaInP/GaInAs/Ge Triple-Junction Solar Cells Using GaInP Back-Surface Field in the Middle Subcell
摘要： This paper studies the radiation resistance for GaInP/GaInAs/Ge triple-junction space solar cells with a GaInP back-surface ?eld (BSF) in the GaInAs middle subcell compared with those with an AlGaAs BSF. The results show that the initial electrical performance is almost the same for both of them. However, the radiation resistance of the GaInP BSF cell was improved. After irradiation by 1 MeV electron beam with a cumulative dose of 1015 e/cm2, the Jsc declined by 4.73% and 6.61% for the GaInP BSF cell and the AlGaAs BSF cell, respectively; the e?ciency degradation was 13.64% and 14.61% for the GaInP BSF cell and the AlGaAs BSF cell, respectively, leading to a reduced degradation level of 6%. The mechanism for GaInP BSF to improve the radiation resistance of GaInP/GaInAs/Ge triple-junction solar cells is also discussed in this work. Similar results were obtained when irradiation cumulative doses varied from 1 × 1014 e/cm2 to 1 × 1016 e/cm2.
关键词： back-surface ?eld,electron beam irradiation,GaInP/GaInAs/Ge triple-junction space solar cell,radiation resistance
更新于2025-09-23 15:19:57
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High-performance lateral MoS2-MoO3 heterojunction phototransistor enabled by in-situ chemical-oxidation; ??????????-|?°§????????oé????§è??MoS2-MoO3é?￠??????è′¨??? è′¨??????????????????;
摘要： Construction of in-plane p-n junction with clear interface by using homogenous materials is an important issue in two-dimensional transistors, which have great potential in the applications of next-generation integrated circuit and optoelectronic devices. Hence, a controlled and facile method to achieve p-n interface is desired. Molybdenum sulfide (MoS2) has shown promising potential as an atomic-layer n-type semiconductor in electronics and optoelectronics. Here, we developed a facile and reliable approach to in-situ transform n-type MoS2 into p-type MoO3 to form lateral p-n junction via a KI/I2 solution-based chemical oxidization process. The lateral MoS2/MoO3 p-n junction exhibits a highly efficient photoresponse and ideal rectifying behavior, with a maximum external quantum efficiency of ~650%, ~3.6 mA W?1 at 0 V, and a light switching ratio of ~102. The importance of the built-in p-n junction with such a high performance is further confirmed by high-resolution photocurrent mapping. Due to the high photoresponse at low source-drain voltage (VDS) and gate voltage (VG), the formed MoS2/MoO3 junction p-n diode shows potential applications in low-power operating photodevices and logic circuits. Our findings highlight the prospects of the local transformation of carrier type for high-performance MoS2-based electronics, optoelectronics and CMOS logic circuits.
关键词： optoelectronics,lateral p-n junction,molybdenum disulfide,photocurrent
更新于2025-09-23 15:19:57
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Comparative analysis of different cooling fin types for countering LED luminaires' heat problems
摘要： A significant problem with high-power LED luminaires is heat. Aluminum heat sinks have been extensively used as a solution. The most common method for heat sinks that increases surface area uses fins. In the present study, pin- and plate-fins were compared and it was observed that, in equal surface areas, better cooling was achieved by pin-fins. Thus, the study’s concentration narrowed to pin-fins and the results of different pin-fins were compared. Simulations of a sample group were conducted by using different numbers of fins, and the number of fins giving the lowest Tmax value (the highest junction point temperature) was accepted to be optimum for each group; then the optimum values were compared among the different groups. Keeping the base width of fins constant, optimum values were obtained for the same number of fins when the fin height was changed. However, keeping fin height constant, surface areas of optimum values and measured Tmax values were very close to one another other, even if the base width of fins was changed. The results have practical significance in designing high-power LED luminaires.
关键词： LED cooling,fin height,junction point temperature,base width,High-power LED luminaire,plate-fin heat sink,pin-fin heat sink
更新于2025-09-23 15:19:57