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Solution-processed semiconductor nanocrystals are evolving as potential candidates for future display and lighting applications owing to their size-tunable emission, ultrasaturated colors, and compatibility with large-area flexible substrates. Among them, quantum rods (QRs) are emerging materials for optoelectronic applications, offering polarized emission, high light outcoupling efficiency, color purity, and better stability in solid films. However, synthesizing QRs covering the full visible wavelength region has been a big challenge, particularly in the blue range. Herein, we report for the first time the synthesis of red CdSe/CdS, green CdSe/Zn

We report the effects of the nitride passivation layer on the structural, electrical, and interfacial properties of Ge metal-oxide-semiconductor (MOS) devices with a hafnium oxide (HfO₂) gate dielectric layer deposited on p-type 〈100〉 Ge substrates. X-ray photoelectron spectroscopy analysis confirmed the chemical states and formation of HfO₂/Ge₃N₄ on Ge. The interfacial quality and thickness of the layers grown on Ge were confirmed by high-resolution transmission electron microscopy. In addition, the effects of post-deposition annealing (PDA) on the HfO₂/Ge₃N₄/Ge and HfO₂/Ge samples at 400 °C in an (FG+O₂) ambient atmosphere for 30 min were studied. After PDA, the HfO₂/Ge₃N₄/Ge MOS device showed a higher dielectric constant (k) of ~21.48 and accumulation capacitance of 1.2 nF, smaller equivalent oxide thickness (EOT) of 1.2 nm, and lower interface trap density (Dit) of 4.9×1011 cm-2 eV-1 and oxide charges (Qeff) of 7.8×1012 cm-2 than the non-annealed sample. The I-V analysis showed that the gate leakage current density of the HfO₂/Ge₃N₄/Ge sample (0.3-1 nA cm-2 at Vg = 1 V) was half of that of the HfO₂/Ge sample. Moreover, the barrier heights of the samples were extracted from the Fowler-Nordheim plots. These results indicated that nitride passivation is crucial to improving the structural, interfacial, and electrical properties of Ge-based MOS devices.

Efficient white light-emitting diodes (LEDs) with an efficacy of 200 lm W

Nano-scale engineering for optoelectronic properties of silicon has shown its suitability in the modern era of Photovoltaic. The major focus is on Silicon quantum dots (Si QDs) which behave like an atom restricting the free movement of electrons. It provides an opportunity to control the energy states by manipulating the size of the Si QDs. Such closely packed Si QDs together form quasi-crystalline structures that lead to the formation of superlattices in different Si energy bands. Significant efforts have been devoted to the control of size and distribution density of the Si QDs. A current status of research efforts on the factors that influence the size and distribution density of Si QDs within the silicon-based matrix are discussed here. A brief summary of various fabrication techniques and mechanisms behind the growth of Si QDs are discussed in this study. A comparison on the effect of growth parameters for Si QDs with various dielectric/semiconductor matrix such as Silicon dioxide, Silicon nitride, Silicon carbide and the combination of the tandem solar cell is highlighted based on recent research progress. An overview towards the state of the art in the development, challenges and future trends of Si QDs to dictate as the third generation photovoltaic material are discussed in detail.

Excellent surface passivation with a localised back surface field (LBSF) formation is the key parameter for increasing the efficiency of PERC cells. In this regard, the additional use of rear multi-stack passivation layers (Al2O3/SiNX) and local laser opening of the LBSF increase the production cost. In addition, these stacked layers and the laser process require additional tools, which creates a compatibility barrier for studies conducted in small-scale industrial laboratories. Rear multi-stack passivation layers (Al2O3/SiNX) and a front SiNX anti-reflection coating (ARC) layer were changed using a one-step thermal oxidation process. The emitter doping and thermal SiO2 oxidation layer were optimised for the front ARC and rear passivation layer. The formation mechanism of the LBSF was investigated by varying the firing conditions and the Al dot size. Scanning electron microscopy images confirmed the thickness of the LBSF. The fabricated cell exhibited an efficiency of 20.05% with a fill factor (FF) of 78%, a current density (JSC) of 39.3 mA/cm2, and an open-circuit voltage (VOC) of 655 mV under a spectral condition of AM 1.5G. A significant improvement in the recombination current density (J0) (314 fA/cm2) was achieved as compared with the fire-through full BSF solar-cell process (933 fA/cm2).

Effects of post deposition annealing (PDA) atmosphere, including oxygen (O2) gas and forming gas (FG), on interfacial and electrical properties of a HfO2 gate dielectric on nitrided Ge are analyzed. Experiments to study the dielectric morphology, interface quality, and chemical composition of HfO2/Ge3N4/Ge devices were carried out using X-ray diffraction, high-resolution transmission electron microscopy (HRTEM) imaging, and X-ray photoelectron spectroscopy (XPS) measurements, respectively. The XPS study confirmed that O2 PDA effectively improves the HfO2 film stoichiometry, and the stability of the interface between HfO2/Ge3N4/Ge stacks is enhanced. Further, HRTEM images showed that the interface between HfO2/Ge3N4/Ge stacks for O2-annealed devices was smooth, uniform, and flat. The experimental results for devices annealed in O2 at 500 °C exhibited improved interfacial and electrical characteristics, such as a high dielectric constant of ~19.50; high capacitance, 1.24 nF, low equivalent oxide thickness, 1.74 nm; interface trap density, 2.18 × 1011 cm−2 eV−1; oxide charges, 2.50 × 1012 cm−2; and gate leakage currents in the order nA of 0.5 × 10−9 A/cm2, as compared with FG annealing devices. The Fowler−Nordheim tunneling current conduction mechanism was also verified. Therefore, these results are evidence that the O2 PDA process improves the interfacial and electrical properties of HfO2/Ge3N4/Ge metal-oxide-semiconductor (MOS) devices as compared with FG annealing, which is important for future Ge-based complementary MOS device performance and reliability.

Effective carrier contact with excellent surface passivation is essential for archiving high efficiency silicon solar cells. In this study, optical, passivation and stoichiometric characteristics of MoOx thin films were analyzed by varying thickness, temperature and ambient annealing. The 10 nm thick MoOx films showed high optical transmittance (89.81%) in the visible near infra-red (NIR) wavelength (380–1100) nm region and wide optical bandgap of 3.25 eV. An improved minority carrier lifetime of 2.24 ms was recorded for O2 ambient at 130 °C due to less additional defects in the MoOx films. X-rays photoelectron spectroscopic analysis confirmed that O2 ambient annealing greatly influenced the MoOx stoichiometric and reduce the formation defective state densities at the Fermi energy initiating from the tail of an oxygen vacancy and inducted the defect band within the energy bandgap. Carrier selective contact (CSC) solar cells were fabricated by using 10 nm thick MoOx film as hole extraction layer exhibited the high performance as; open circuit voltage (Voc) = 708 mV, current density (Jsc) = 37.80 mA/cm2, fill factor (FF) = 74.95% and efficiency (η) = 20.06%. These results implies that the MoOx is an important material to use in future CSC solar cell applications with the concept of new advantages such as dopant free, non-toxic and low temperature fabrication process.

Transition metal oxides (TMO) are extensively applied as a surface passivation and carrier-selective contact layer through replacing boron/phosphorus doped emitter layers in silicon heterojunction (SHJ) solar cell applications. In this regard, molybdenum oxide (MoO3) has drawn a significant attention as a hole extraction layer owing properties such as wide bandgap (∼3 eV), high work function (>6 eV) and low temperature deposition. Thus, we fabricated SHJ solar cells with a dopant-free MoOx applied at the front surface contact layer. Thermally evaporated MoOx films were exhibited optical characteristics such as high transmittance, high bandgap and low absorption coefficient as compared to a-Si:H(p) and μc-SiOx:H (p) layers. X-ray photoelectron spectroscopy (XPS) analysis confirmed the stoichiometric and oxidation deficiency states of the of the MoOx layers. Whereas, MoOx films undergoing long-term air exposure showed an increase in Mo5+ cations due to the increased oxygen vacancy. The fabricated MoOx/c-Si heterojunction solar cells achieved a significant power conversion efficiency (η) of 20%, best open circuit voltage (Voc) of 695 mV, high short circuit current density (Jsc) of 38.88 mA/cm2 and a fill factor (FF) of 74.0%. These results implying that MoOx is as an excellent dopant-free material for alternate p-doped a-Si:H emitter layers in SHJ solar cell applications.

In silicon heterojunction (SHJ) solar cells, a wide bandgap material with a high work function is widely used as the hole extraction pathway to attain high efficiency. We introduced a molybdenum oxide (MoOx) film as an effective hole-transfer layer in carrier selective contact (CSC) solar cells by virtue of its wide bandgap along with high work function. The passivation characteristics, optical and electrical properties of MoOx films were investigated by differing thickness and work function. The combination of 6 nm hydrogenated intrinsic amorphous silicon (a-Si:H(i)) and 7 nm thermally evaporated MoOx passivation layers provides excellent passivation properties, reduces carrier recombination, and improves the cell performance. The synthesized CSC solar cells showed promising results, with an open-circuit voltage (Voc) of 708 mV, short-circuit current (Jsc) = 37.38 mA cm−2, fill factor (FF) = 74.59%, and efficiency (η) = 19.75%. To justify the obtained result, an AFORS HET simulation was conducted based on the experimental results. The high work function and wide bandgap MoOx/c-Si(n) interface developed a considerable built-in potential and suppressed the electron–hole pair recombination mechanism. The CSC solar cell’s simulated performance was enhanced from 1.62 to 23.32% by varying the MoOx work function (ΦMoOx) from 4.5 to 5.7 eV.

Excellent surface passivation and carrier selective contact formed by the metal oxide induced junctions is required for future high efficiency silicon solar cells. Due to wide optical bandgap and high work function of molybdenum oxide (MoOx, x

Front side textured random pyramids are widely utilized in major industries for the performance enhancement of crystalline silicon (c-Si) solar cells. Random pyramids not only reduce the surface reflectance but also improve the light trapping effect. Therefore, it is necessary to understand the pyramid height affecting the cell performance, further improving cell efficiency. In this work, we present an experimental study to investigate the influence of pyramids size on the contact shading loss mechanism of silver (Ag) screen-printed p-type c-Si solar cells. Three alkaline texture solutions with sodium silicate additives were optimized to develop the small pyramid (0.5–2.0 µm) size, middle pyramid (5.0–9.0 µm) size and large pyramid (10–15 µm) size on the c-Si surface, respectively. It was noticed that screen-printed finger width strongly depends on pyramid size. Even though, same mesh patterns and screen printing conditions resulted in 20 µm widening of metal finger width on the large pyramids as compared to the small pyramids. This was attributed to the increase in the size of cell surface pyramids that not only varied the gap between the screen mesh and cell surface while screen-printing but also hindered the contraction of metal electrodes during the firing process. The c-Si solar cells with large pyramids suffered from an extra shading loss during fabrication, thus, led to the reduction of the short circuit current density (~0.7 mA/cm2) resulting in lower efficiency (~17.72%) as compared to efficiency (~18.60%) of small pyramid based cells.

We report an efficient light trapping for maskless large area randomly textured glass structures with various haze ratios in silicon thin film solar cells. By well controlling the ratio of buffered hydrofluric acid (BHF) and sulfuric acid (H2SO4), we were able to prepare the randomly textured maskless glass structures with high transmittance above 90% and variable haze ratio from 20.79 to 54.78% in the visible wavelength (380–800 nm) region. It was observed that haze ratio of textured glass was dependent on feature size, etching depth and rms roughness. Multi-textured aluminum-doped zinc oxide (AZO) films were deposited on textured glass structures showed high transmittance (83.78–85.06)% and haze ratio (45.03–65.05)% in visible wavelength region. An enhancement in haze ratio of multi-textured AZO films was due to an increase of rms roughness from 16.4 to 185.5 nm as shown by 3D-alpha step profiler images. Multi-textured AZO films deposited on various textured glass superstrates were employed as a front transparent conductive oxide (TCO) layer for the fabrication of amorphous silicon (a-Si) thin film solar cells (TFSCs). The a-Si TFSCs deposited on structure-C glass showed the maximum performance as; open circuit voltage = 869 mV, short circuit current density = 16.68 mA/cm2, fill factor = 67.8% and efficiency = 9.79%. An enhancement of photocurrent was noticed from 15.64 to 16.68 mA/cm2 for as deposited a-Si TFSCs to structure-C based a-Si TFSCs.

We report the light scattering characteristics of multi-textured aluminum-doped zinc oxide (AZO) thin films with high optical transmittance, haze ratio and step coverage for amorphous silicon thin film solar cells (a-Si TFSCs). Multi-textured AZO films were deposited on inverted hemisphere textured (IHT) glass surface morphologies. Multi-textured process was used to create modulated surface morphologies with micro and nano-features useful for the light scattering in visible as well as near-infrared wavelength region. Highly transparent IHT glass surface morphologies with high haze ratio were prepared by wet chemical etching of periodic glass substrates. Total transmittance of the IHT glass substrates showed higher average values (91.38–93.40%) as compared to that of bare glass (90.94%) in the visible wavelength region due to lower reflectance. Multi-textured AZO films showed higher rms roughness 100.479 nm, optical transmittance 82.60% and haze ratio 75.09% in the visible wavelength region. X-ray photoelectron spectroscopic analysis of multi-textured AZO thin films was used to study the atomic compositions and chemical binding states. Multi-textured AZO films with high transmittance and haze ratio were used as front transparent conductive oxide layers for the fabrication of a-Si TFSCs using an absorber layer thickness of 400 nm. Multi-textured AZO films deposited on the optimal textured glass surface morphologies yield the maximum performance of a-Si TFSCs as; Voc = 871 mV, Jsc = 16.55 mA/cm2, FF = 66.6% and η = 9.61%. An enhancement of photocurrent was noticed from 15.64 to 16.55 mA/cm2 for the a-Si TFSCs deposited on as deposit AZO to optimal textured AZO films.

Efficient white light-emitting diodes (LEDs) with an efficacy of 200 lm W-1 are much desirable for lighting and displays. The phosphor-based LEDs in use today for display applications offer poor color saturation. Intensive efforts have been made to replace the phosphor with quantum-dot-based downconverters, but the efficiency and stability of these devices are still in their infancy. Quantum rods (QRs), nanoparticles with an elongated shape, show superior properties such as relatively larger Stokes shifts, polarized emission, and high light out-coupling efficiency in the solid-state. However, these QRs usually suffer from poor optical quality for PL wavelengths

We report the effects of the nitride passivation layer on the structural, electrical, and interfacial properties of Ge metal-oxide-semiconductor (MOS) devices with a hafnium oxide (HfO₂) gate dielectric layer deposited on

We report the controllable charge (Electron/hole) trapping window layer properties of atomic layer deposited (ALD) aluminum oxide (Al2O3) gate dielectric layer on the Si substrate. Electron/hole blocking mechanism was archived by controlling the Al 2 O 3 composition, band gap and post deposition annealing affect, respectively. The chemical composition of the Al 2 O 3 was confirmed from the X-ray photoelectron spectroscopy analysis. The capacitance-voltage (C-V) characteristic of Al/Al 2 O 3 /Si (MOS) metal-oxide-semiconductor structure showed clear accumulation, depletion and inversion regions as-compared with the Al/SiN x /Si MOS devices, respectively, From the C-V curves, the flat band voltage(Δ FB ) was shifted accordingly positive and negative with respect to electron/hole trapping effect. In addition, 10 nm AlOx storage layer and SiN x storage layer were compared in the same structure. The 10 nm SiN x storage layer showed a very low retention of 55.1% and the memory window also showed a relatively low value of 2.72V at 18V.

An ultra thin surface passivation layer is essential to reduce the surface recombination and enhance the open circuit voltage for high efficiency crystalline silicon (c-Si) solar cells. In that, we developed charge injection controllable thin films of SiO X and SiN X layers by PECVD for surface passivation of boron emitter c-Si surface. The refractive index of the SiO X /SiN X stack was optimized by varying the SiH 4 , NH 3 and N 2 O gas ratios. Lower D it of 5 × 1010 cm−2 eV−1 and high Q eff of −1.71 × 1011 cm−2 was obtained for 10 nm thick SiO X layer. The fabricated n-Si bifacial cell with insertion of 10 nm thick SiO X layer archived efficiency (η) of 19.48 % with fill factor (FF) of 77.5 %, whereas the cell without SiO X layer showed an η of 18.20 % with FF of 75.77.

Ultra-thin MoO x is capable of exhibiting high work function ( x electronic structure by oxygen dilution during the evaporation have influence to the MoO x work function and hence reduce hole injection. XPS study confirmed the electronic structure and chemical composition of the evaporated and annealed (Ar and O 2 atmosphere) MoO x sample. TEM showed a clear interface contact between the ITO/MoOx/a-SiH(i) layers and no diffusion between the layers after annealed at 140 °C. Fabricated 10 nm thick MoO x /n-Si solar cells archived an efficiency of 20.04%, FF of 73.79 % and J sc of 38.40 mA/cm2. A sever degradation in FF and J sc was noticed by increasing the MoO x thickness due to diffusion of layers and high parasitic absorption of MoO x .

It has been a hot debate in recent time whether periodic or random TCO surface morphology showed better light scattering in silicon thin film solar cells (TFSCs). We report an advanced light scattering scheme by various textured glass surface morphologies with high transmittance, haze ratio in visible as well as in near infra-red (NIR) wavelength region for the applications of silicon TFSCs. Three different textured (trapezoid, pyramid and random) glass surface morphologies with high transmittance, rms roughness and haze ratios were selected. The textured glass surface morphologies showed higher optical transmittance (91.77 to 93.04%) as compared to bare glass transmittance (90.94%) in the visible wavelength region. It was observed that the haze ratio was reliant on the surface feature size, etching depth, spacing and rms roughness of glass surfaces. Multi-textured AZO films deposited on micro textured glass surfaces showed higher transmittance 83.78% and haze ratio of 65.06% in the visible wavelength region. The X-ray photoelectron spectroscopic analysis was performed in order to investigate changes in the composition of textured glass surfaces. Amorphous silicon (a-Si) TFSCs were fabricated on periodic and random textured glass surface morphologies showed higher current density (16.55 and 16.68 mA/cm2) and efficiency (9.61 and 9.79%), respectively. Due to higher transmittance, haze ratio, high rms roughness and better step coverage, we propose these textured glass surface morphologies for high efficiency amorphous and microcrystalline based silicon thin film solar cells.

We report the effects of post deposition annealing (PDA) ambient O2 and FG gas on interfacial and electrical properties of HfO2 gate dielectric on nitrided Ge. The morphological studies of the dielectric, interface quality and chemical composition of the HfO2/Ge3N4/Ge were studied from X-ray diffraction (XRD), High-resolution transmission electron microscopy image (HRTEM) and X-ray photoelectron spectroscopy (XPS) respectively. Experimental results of O2 annealed devices exhibit improved interfacial and electrical characteristics such as high dielectric constant (~19.50), high capacitance (1.24 nF), small EOT (1.74 nm), Dit (3.18x1010 cm2 eV-1), oxide charges (Qeff 2.60x1012 eV-1) and gate leakage currents in the order nA (0.5x10-9 A/cm-2) as compared with FG annealing devices. The Fowler−Nordheim (F−N) tunnelling current conduction mechanism was also verified. Therefore, these results are evidence for the O2 gas PDA improves the interfacial and electrical properties of HfO2/Ge3N4/Ge MOS devices as compared with FG annealing.