Optoelectronic Characteristics Research Articles

Enhanced optoelectronic characteristics of La-doped ZnO and its compatibility with Cs-doped MAPbI3 perovskite absorber material

Abstract The present study investigates the structural, electrical and optical characteristics of pristine and lanthanum (La)-doped zinc oxide electron transport layers (ETLs) fabricated by the sol gel method and their compatibility with Cs0.10MA0.90Pb(I0.9Br0.10)3 absorber layer for perovskite solar cells. All the ETLs were deposited under same deposition conditions, with the only difference in La percentage in the precursor solutions, ranging from 0 to 6%. X-ray diffraction (XRD) analysis demonstrated the presence of crystalline ZnO thin films and the absence of any impurity phases after La-doping. The calculated crystallite size, determined using Scherrer’s equation, increased from 11.13 to 21.76 nm after the introduction of dopant. The doping with 4% La led to the decrease in the optical bandgap from 3.32 eV of pristine ZnO to 3.23 eV. SEM analysis revealed better morphology of perovskite/4% La:ZnO specimen, which facilitated the absorbance and reduced the charge carrier recombination. It also exhibited superior resilience towards moisture and humidity which will eventually contribute to the development of more stable and efficient planar perovskite solar cells (PCSs).

Comprehensive evaluation of mechanical properties, optoelectronic features, photovoltaic performance, and crystal stability of Ba3MX3 (M = As, Sb; X = Cl, Br, I)

Herein, the first-principles computations are utilized to study the optoelectronic properties, photovoltaic performance, crystal stability, and mechanical features of Ba3MX3 (M = As, Sb; X = Cl, Br, I). Through comprehensive structural stability evaluation, all compounds are determined to be stable. The results indicate that Ba3MX3 (M = As, Sb; X = Cl, Br) is brittle while both Ba3AsI3 and Ba3SbI3 are ductile. The HSE06-based electronic structure calculations show that the direct-gap nature is revealed for six compounds, and the energy band gaps are within the range of 1.35–1.65 eV. The fundamental band gap can be modulated by virtue of X-anion substitution. The low carrier effective masses are disclosed for these compounds. Their optical features exhibit that high solar absorption and weak reflectance and energy loss are observed. Ultimately, an ultra-high theoretical conversion efficiency of 31.9 % is implemented for Ba3MI3 (M = As, Sb). Besides, the remaining four compounds also have high conversion efficiencies within 29–30 %. From the suitability for practical applications, both Ba3AsI3 and Ba3SbI3 are chosen as the best candidates for the absorber layers of effective single-junction solar cells. Our findings unveil the suitability of these inorganic materials for optoelectronic applications.

Tunable electronic and optoelectronic characteristics of two-dimensional g-GeC monolayer: a first-principles study

Two-dimensional (2D) semiconductor materials have emerged as one of the hotspots in recent years due to their potential applications in beyond-Moore technologies. In this work, we systematically investigate the electronic and optoelectronic properties of the g-GeC monolayer combined with strain engineering using first-principles calculations. The results show that g-GeC monolayer possesses a suitable direct bandgap and a strain-tunable electronic structure. On this basis, the designed g-GeC monolayer-based two-probe photodetector exhibits a robust broadband optical response in the visible and near-ultraviolet ranges, along with significant polarization sensitivity and high extinction ratio. In addition, strain engineering can greatly improve the optoelectronic performance of the g-GeC-based photodetector and effectively tune its detection range in the visible and near-ultraviolet regions. These findings not only deepen the comprehension of g-GeC nanosheet but also provide the possibility of its application in nano-optoelectronic devices.

The impact of charge carrier dynamics on the outdoor performance of cesium-lead-halide perovskite photovoltaics

We investigated the optoelectronic characteristics of cesium-based perovskite using various techniques. The steady-state photoluminescence (PL) spectroscopy of this perovskite solar cell composition shows the presence of strong peaks at a wavelength of 759 nm, which that corresponds to a band gap energy 1.63 eV. This band gap energy was estimated using two complementary methods, the PL emission spectra and the UV–vis absorption spectra. The study describes the dependence of photon energy on wavelength using a Gaussian mathematical model. Real-outdoor performance testing was conducted in Ethiopia’s climate during the hottest seasons to study the device performance under outdoor conditions at varying irradiances. Moreover, we investigated power generation from the devices using current–time measurements and analyzed charge carrier dynamics through transient photocurrent measurements.

Elucidating the Advancement in the Optoelectronics Characteristics of Benzoselenadiazole-Based A2-D-A1-D-A2-Type Nonfullerene Acceptors for Efficient Organic Solar Cells.

The potential applications of nonfullerene acceptors (NFAs) such as tunable band gaps, improved charge separation, wide-range absorption, enhanced power conversion efficiency, and operational stability make them highly favorable for organic photovoltaic applications. Herein, we designed eight novel structurally modified nonfused benzoselenadiazole (BSe)-based A2-D-A1-D-A2-type NFAs for efficient organic solar cells (OSCs). These newly modeled BSe-based NFA series contain BSe as the central core. We employed strong electron-withdrawing moieties at terminal acceptor A2 to further enhance the optical, optoelectronics, and photovoltaic characteristics of OSCs. These designed molecules (HNM1-HNM8) along with the synthetic reference molecule (HNM) were thoroughly characterized by using efficient and advanced quantum chemical simulation approaches. Thus, to ascertain the enhancement of both optical and photochemical response, a thorough density functional theory (DFT) study was carried out using the M062X level in association with the 6-31G(d,p) basis set. All of the investigated molecules (HNM1-HNM8) had their excited states calculated using the time-dependent density functional theory method. The newly designed molecules (HNM1-HNM8) presented narrower band gaps, improved absorption and optoelectronics properties, and reduced excitation and binding energies. The electrostatic potential, density of states, transition density matrix, ionization potential, and electron affinity analysis of this newly designed (HNM1-HNM8) series revealed a strong coherence with those of the reference HNM molecule. Electron density difference mapping allowed us to visualize the spatial movement of electrons between the donor and acceptor molecules during excitation. This insight helps us to understand the efficiency of charge separation and recombination processes that are critical for the performance of organic photovoltaics. The reorganization energy and charge transfer analysis suggests that HNM1-HNM8 molecules could act as NFAs for organic photovoltaic applications to enhance their efficiency further. The donor: acceptor charge transfer analysis was also carried out, which revealed that the PTB7-Th:HNM2 donor:acceptor complex shows a great charge transportation process at the donor-acceptor interface. Moreover, the photovoltaic analysis shows that the designed (HNM1-HNM8) NFA series has a great potential to produce improved open-circuit voltage and fill factor values, which may be helpful in enhancing the overall PCEs of the OSCs.

Gate voltage dependence on the density of state of 30° twisted bilayer graphene using Trotter–Suzuki tight-binding time propagation method

Abstract Twisted multilayer structures are considered a helpful framework for exploring strongly correlated many-particle systems, where phenomena of physics correlation emerge. Here, we present the Trotter–Suzuki tight-binding time propagation method for computing the density of states (DOS) in a 30° twisted bilayer graphene (TBG). This method solves the time-dependent Schrödinger equation by decomposing Hamiltonian matrices to derive the correlation function. The Fourier transform of this correlation function yields the DOS of the system up to ≈ 1000 000 atoms. Our calculation proves that geometry makes an outstanding contribution to our final results. Additionally, applying additional gate voltage induces shifts in Van Hove singularities, potentially leading to the emergence of new states at the Fermi energy level. The results demonstrate that TBG systems can be easily adjusted and modified for further investigation of optoelectronic features.

The Impact of Hydrostatic Pressure on the Structural, Mechanical, Thermal, and Optoelectronic Characteristics of the RbV3Sb5 Kagome Compound: Ab initio Approach.

We studied the RbV3Sb5 kagome compound's structural, mechanical, thermal, and optoelectronic properties. Mulliken and Hirshfeld population analysis found ionic and covalent connections in RbV3Sb5. The Born stability criterion shows that pure RbV3Sb5 is mechanically stable. The precise measurement of 3.96 indicates that our sample has higher machinability at 20 GPa. Low anticipated hardness of RbV3Sb5 suggests it can be used as a soft solid lubricant. Hardness ratings rise with pressure, however there are exceptions. Pressure causes large nonmonotonic changes in RbV3Sb5's anisotropic characteristics. A comparable 20 GPa Zener anisotropic value, RbV3Sb5 has the highest. The structure's projected Debye temperature at 0 GPa is 284.39 K, indicating softness. Dispersion curves with negative frequencies suggest ground state structural dynamical instability. The structure has no negative-energy phonon branches under 10 GPa stress. From band structure and density of state analysis, the structure behaves metallically under hydrostatic pressure. Also, the structure has maximal ultra-violet conductivity and absorption. The absorption coefficient, conductivity, and loss function plots show uniform patterns at all pressures. As pressure rises, these graphs' peaks blue shift.

Fused Hexabenzocoronene-Porphyrin Conjugates with Tailorable Excited-State Lifetimes.

A new clear-cut strategy for fusing N-heterocyclic and carbon-pure systems is introduced en route to a versatile platform of multi-purpose tetrapyrrolic chromophores. In particular, three novel C-C bond-fused porphyrin-hexabenzocoronene (HBC) conjugates were synthesized under oxidative cyclodehydrogenation conditions, starting from tailor-made nickel porphyrin precursors. The fusion of the individual aromatic systems via 5-membered rings led to highly soluble π-extended porphyrins in excellent yields. The resulting porphyrin-HBC conjugates exhibit absorption cross-sections that are of interdisciplinary interest in the ever-growing field of organic photovoltaics and near-infrared (NIR) dyes. Quantum chemical calculations show that the newly formed 5-membered rings induce biradicaloid character in the porphyrin core, which has a strong impact on excited state lifetimes. This is confirmed by a thorough optoelectronic and time-resolved characterization in order to understand these unique features better. Broadened absorption characteristics go hand-in-hand with short-lived excited states with up to six orders of magnitude faster decay rates.

Modulating the optoelectronic characteristics of ZnS through transition metals doping: insights from density functional theory

Modulating the optoelectronic characteristics of ZnS through transition metals doping: insights from density functional theory

Space‐ and Time‐resolved Emission Features of Micro‐ and Nano‐sized Perylene‐based Zr Metal‐Organic Frameworks

AbstractWhile many photoresponsive metal‒organic frameworks (MOFs) have been reported to date, finding applications in several technologically relevant fields such as photocatalysis, sensors, and light‐emitting devices, significantly scarcer are the reports addressing the relationship between the MOFs emissive features and their crystalline domain size (i.e., micro‐ and nano‐sized materials). Herein, a valuable contribution is offered to this issue which consists of the use of reticular chemistry to prepare a Zr‐MOF featuring spatially separated tetracarboxylated‐functionalized perylenes as ligand. Single crystal X‐ray analysis of such Zr‐MOF revealed the formation of micro‐ and meso‐porous channels. The perylene‐based Zr‐MOF exhibited notable optoelectronic features, including a relatively small optical bandgap of 1.82 eV and emission features different from that of the constituting perylene ligand in the solid state. Additionally, local probe techniques are used to unveil the emission properties of isolated Zr‐MOF crystals. Space‐ and time‐resolved fluorescence studies revealed a strong dependence of the emissive features of the Zr‐MOF, both in terms of its intensity and lifetime, to the crystalline domain size.

DFT study of halogen based double perovskite Na2AgAlX6 (X = Cl, Br, I) double perovskites for energy harvesting applications

Abstract Double perovskites halides show a lot of potential for being utilized in energy converting applications. This research offers a wide-ranging analysis of photovoltaic features of halogen based double perovskite Na2AgAlX6 (X = Cl, Br, I) by employing DFT approach. Structural, thermoelectric and optoelectronic features of Na2AgAlX6 have been analyzed in this report. The structural stability of the investigated materials is verified by Born's stability criterion. The ductility of Na2AgAlX6 is confirmed by the Poisson coefficient ( >0.27) and a Pugh ratio (B/G>1.83). The bandgap 3.7 eV, 2.7 eV, and 1.3 eV of Na2AgAlX6 (X = Cl, Br, I) has been observed with direct nature. The replacement of Br and I with Cl leads to the lowering of bandgap value because it brings the edges of the band closer together. The absorption factor, reflective properties, and dielectric parameters are used to evaluate the optical features. The BoltzTraP software played vital role in calculating the thermoelectric characteristics, such as ZT value, power factor, and their electrical and thermal conductivities.The results of these calculated properties indicate that Na2AgAlX6 (X = Cl, Br, I) double perovskite halides show a promising potential for energy renewable applications.

Exploration of the structure, electronic and optical properties of AB 2(PO3)5 polyphosphates: a first-principle approach

The density functional theory method was applied using the gradient PBE, incorporating the hybrid PBE0 functional along with dispersion corrections D3(BJ). These objectives were accomplished through the utilization of the CRYSTAL package, employing a localized atomic orbital basis. Calculations encompassing crystal properties, including electronic, structural, and linear/nonlinear opto-electronic characteristics, were conducted for monoclinic AB 2(PO3)5. Specifically, the polyphosphates investigated in this study are RbPb2(PO3)5, CsPb2(PO3)5, KBa2(PO3)5, and RbBa2(PO3)5. It was demonstrated that in monoclinic phosphates, phosphorus and oxygen atoms form infinite chains [PO4]∞ based on the· ⋯ O1-P-O1 ⋯ ·structure. Alkali metal and lead (barium) atoms are surrounded by oxygen atoms O2, forming polyhedra. Infrared absorption spectra calculations confirmed the presence of chain backbone structural units. Additionally, band structure and partial density of electronic states were determined. The nature of valence and unoccupied states was also investigated. In lead-doped compounds, lead atoms contribute to the formation of upper-valence and lower-unoccupied states. Conversely, in barium-doped compounds, the upper valence states are primarily formed by O2 p-states, while the lower unoccupied states are formed by phosphorus. Also, the coefficients of second harmonic generation and birefringence were calculated, assessing the potential use of phosphates as nonlinear optical materials.

Atomistic insight into the device engineering of inorganic halide perovskite solar cells

Perovskites provide a promising pathway for fabricating efficient and lightweight solar cells, which could be game-changers in the renewable energy landscape. Yet, the phase stability and device design are still the key issues of perovskite-based photovoltaics. Herein, we evaluated the phase stability of CsPbX3 (X = I, Br, and Cl) upon analyzing the lattice dynamics from first-principles and then predicted fundamental properties including bandgap, carrier mobility, and optical absorption as input to optimize the device design of solar cell. A maximum power conversion efficiency (PCE) of 12.36 % was achieved for a CsPbBr3-based solar cell. Those findings highlight the potential of CsPbX3 perovskites for high-efficiency solar cells. The computational approach provides a comprehensive understanding of the material's structural stability, charge-carrier dynamics, and optoelectronic characteristics. The collective analysis enables a holistic understanding of CsPbX3 perovskites and provides a roadmap for future advancements in perovskite solar-cell technology.

Influence of bottom supporting columns and cooling rate on the surface shape characteristics of sapphire substrates

The manufacturing process of sapphire substrates involves several key steps, including epitaxy, annealing, cutting, and processing. Among these, epitaxy and annealing are particularly crucial. The temperature variances along both the longitudinal and transverse axes within the furnace during the crystallization process play a significant role in determining the crystallization rate and internal structure of sapphire crystals. Furthermore, annealing sapphire serves to alleviate internal stress, enhance crystal structure, optimize physical properties, improve optoelectronic characteristics, enhance surface quality, and increase overall yield. This step is paramount in enhancing the performance and application value of sapphire materials. In order to investigate and optimize the effects of different thermal conductivities of support columns at the base and various annealing procedures on the surface characteristics of sapphire substrates, thereby improving product quality, this study conducted research by utilizing support columns made of different materials and carefully controlling the cooling rate parameters for sapphire. The findings revealed that using graphite as the base support column for the crystal furnace can reduce both the longitudinal and transverse temperature gradients within the furnace, consequently promoting crystal growth and enhancing the quality of sapphire ingots. Additionally, sapphire chips annealed using the rapid one-step annealing program exhibited the highest average warpage and bending rate variation, reaching 2.0 μm, and the average dislocation density was half that of conventionally produced chips, at 108.89 pits/cm2.

Histidine-based hybrid perovskites as promising materials for wide wavelength photodetection

Layered 2D hybrid organic-inorganic perovskites (2D-HOIPs) exhibit a distinctive array of properties, including remarkable structural flexibility, enhanced resistance to moisture, and optoelectronic characteristics valuable for practical applications. Consequently, these materials are now widely acknowledged as pivotal components in optical and optoelectronic technologies. However, a significant drawback of 2D-HOIPs is their wide band gaps that has hindered their widespread application in optoelectronic devices. In this work we address this limitation by offering a novel series of 2D mixed-halide tin-based HOIPs with general formula (L-HisH)2SnBrxI4−x (where L-His = L-histidine, x = 4, 3.37, 1.70, 0.56, 0.44, and 0) for which the band gap can reach record narrow values, which are not typical for 2D-HOIPs. These compounds can be easily obtained in wide compositional range by implementing halide substitution approach. Each hybrid perovskite features a chiral structure imparted by chiral L-histidinium(+) cations interleaved between corner-shared tin halide octahedra, organized into single-layer thin inorganic slabs. Crucially, these new materials provide a high degree of flexibility in tuning their band gaps throughout the entire visible light spectrum, encompassing a range between 1.82 and 3.05 eV. As a “proof-of-concept”, we created a prototype HOIPs photodetector in which this HOIP was used as an active layer. It is noteworthy that the band gap of pure iodide perovskite is surprisingly narrow for this class of materials. The production of semiconductor materials with a variable width of the optical bandgap is the key to more versatile and diverse applications of these materials in the active components of modern optoelectronic devices. For the obtained prototype, light detection is observed in the wide range covering UV, visible and near-IR regions, marking a record achievement for 2D-HOIPs. Beyond photodetectors, these new histidine-based perovskites hold promise for applications in various other optoelectronic devices, including solar cells, photodiodes, phototransistors, polarized light detectors, and more.

Investigating the structural, electronic, optical and thermodynamic properties of ATiO3 (A = Ba, Ca, Ra) for low-cost energy applications

The structural, optoelectronic, and thermodynamic characteristics of ATiO3 (A = Ba, Ca, Ra) perovskites have comprehensively been investigation first-principles based DFT calculations. The GGA method was employed to handle exchange and correlation potentials. The analysis of the E-V plots indicates that RaTiO3 exhibits the highest level of stability in comparison to BaTiO3 and CaTiO3. The direct band-gap characteristic of the ATiO3 (A = Ba, Ca, Ra) perovskites is apparent in the band structure plots. The band gaps for BaTiO3, CaTiO3, and RaTiO3 are 2.48, 3.15, and 1.91 eV, respectively. The analyzed materials exhibit the highest level of photon absorption in the near UV area, as demonstrated in the ε2(ω) plots. The refractive index n(ω) values reveal that ATiO3 (A = Ba, Ca, Ra) are active optical materials as their n(ω) values are between 1 and 2. These perovskite oxides have optical features that make them promising prospects for anti-reflecting coatings over entire energy span as these materials exhibits a very low reflection (∼20 %) of incident photons. The thermodynamic properties of ATiO3 (A = Ba, Ca, Ra) are assessed to determine their dynamical stability and suitability for thermal applications. The results of the investigation demonstrate that these perovskite oxides have the potential to be used in optoelectronic devices.

Photodetector application of CuO nanoparticles on porous silicon fabricated by laser ablation in liquid at diverse laser energies

Abstract This paper describes the synthesis and analysis of a photodetector made of copper oxide nanoparticles (CuONPs) embedded in a porous silicon (PS) matrix. CuONPs were generated utilizing pulsed laser ablation in ethanol (PLAL), while a porous silicon-(PS) substrate was created via photo-assisted electrochemical etching. An investigation is conducted on the optical, structural, and electrical characteristics of CuONPs/PS devices, with a focus on their dependence on laser energy. The X-ray diffraction analysis reveals the presence of distinct peaks associated with a copper cubic structure, demonstrating the successful synthesis of CuONPs that have been deposited onto PS. The study using field emission scanning electron microscopy revealed that the particles exhibited spherical form. The CuO-nanocolloids exhibited a linear relationship between laser power and absorption, and their surface plasmon resonance peaks were clearly visible at 570–590 nm. Band gaps of 1.70, 1.61, 1.81, and 1.90 eV were found for CuONPs produced at 500, 600, 700, and 800 mJ of laser energy, respectively, according to the optical characteristics. The greatest responsivity of the CuO-NPs/PS photodetector, manufactured at an energy level of 700 mJ, was 0.135345 A/W at 450 nm, as determined by the optoelectronic characteristics. As a result of combining PS with CuONPs, the devices shown in this work have the ability to function as highly efficient photodetectors.

Structural, Morphological, and Optoelectronic Properties of RF Sputtered AZO Thin Films on Glass and Polymer Substrates: A Comparative Study

This paper investigates the thickness-dependent structural, morphological, and optoelectronic properties of Al-doped ZnO (AZO) thin films deposited on glass and flexible polyethylene terephthalate (PET) substrates via confocal magnetron sputtering. The film’s thickness ranged from 50 to 130 nm. X-ray diffraction results show that all AZO films on glass have better structural properties than those on PET. Furthermore, the (002) peak intensity and crystallite size on both substrates improved progressively with thickness. Field emission scanning electron microscopy and atomic force microscopy images revealed that the film morphology and surface roughness are dependent on substrate and thickness. According to the UV–vis-NIR measurement results, the air-referenced transmittance spectra of films on PET were slightly lower than those on glass; however, compared to films on glass, the substrate-referenced transmittance of PET films was higher. Moreover, for both substrates, it is found that the bandgap of fabricated thin films decreases with thickness. Photoluminescence spectra show that for glass and PET substrates, the total luminescence of AZO decreases with increasing film thickness and that green and red emissions are absent from AZO films deposited on PET substrates. AZO films deposited on glass substrates exhibit superior electrical and optoelectronic characteristics.

Optoelectronic characteristics of In2O3/CuO thin films for enhanced vis-light photodetector

Optoelectronic characteristics of In2O3/CuO thin films for enhanced vis-light photodetector

Modulating Eco-friendly Colloidal AgGaS2 Quantum Dots for Highly Efficient Photodetection and Image Sensing via Direct Growth of Ternary AgInS2 Shell.

Tailoring the optoelectronic characteristics of colloidal quantum dots (QDs) by constructing a core/shell structure offers the potential to achieve high-performing solution-processed photoelectric conversion and information processing applications. In this work, the direct growth of wurtzite ternary AgInS2 (AIS) shell on eco-friendly AgGaS2 (AGS) core QDs is realized, giving rise to broadened visible light absorption, prolonged exciton lifetime and enhanced photoluminescence quantum yield (PLQY). Ultrafast transient absorption spectroscopy demonstrats that the photoinduced carrier separation and transfer kinetics of AGS QDs are significantly optimized following the AIS shell coating. As-synthesized environmentally benign AGS/AIS core/shell QDs are employed to fabricate photodetectors (PDs), showing a remarkable responsivity of 38.4 AW-1 and a detectivity of 2.4×1012 Jones under visible light illumination (405 nm). Moreover, the fabricated QDs-PDs exhibit superior image-sensing capability to record complex patterns with high resolution (160×160 pixels) under visible light illumination at 405 and 532 nm. The findings indicate that the direct growth of multinary narrow-band shell materials on eco-friendly QDs holds great promise to implement future "green", cost-effective and high-performance optoelectronic sensing/imaging systems.