Related Optoelectronic Properties Research Articles

Copper(I) TADF exciplexes via Metal-Perturbed Through-Space charge transfer for efficient OLEDs

Organo-copper(I) emitters are promising cost-effective candidates as triplet-harvesting dopants in organic light-emitting diodes (OLEDs). To date, the mainstream design of Cu(I) emitters depends on ligand engineering to modify intramolecular charge transfer and thus modulate the related optoelectronic properties. However, little is known on luminescent Cu(I) systems based on intermolecular charge transfer. For the first time, the proof-of-concept Cu(I) exciplexes were developed employing a triazine-containing molecule DMIC-TRZ as an acceptor and several Cu(I)-based carbene-metal-amide (CMA) complexes as donors. The formation of these exciplexes is strongly associated with d-orbital participation of Cu atom on the highest occupied molecular orbital of CMA complexes to match with the acceptor DMIC-TRZ. These Cu(I) exciplexes not only displayed donor-dependent emission colors spanning from sky blue to red but also exhibited distinct thermally activated delayed fluorescence (TADF) via copper(I)-perturbed through-space charge transfer (TSCT). The OLEDs adopting the Cu(I) exciplexes as emitters delivered good external quantum efficiency (EQE) of up to 10.9%. Furthermore, the use of these Cu(I) exciplexes as hosts for multi-resonance TADF emitters delivered narrowband electroluminescence with high EQEs of up to 24.9%, superior to the reference OLEDs based on the common host.

Research on Infrared Emissivity and Laser Reflectivity of Sn1−xErxO2 Micro/Nanofibers Based on First-Principles

Sn1−xErxO2 (x = 0%, 8%, 16%, 24%) micro/nanofibers were prepared by electrospinning combined with heat treatment using erbium nitrate, stannous chloride and polyvinylpyrrolidone (PVP) as raw materials. The target products were characterized by thermogravimetric analyzer, X-ray diffrotometer, fourier transform infrared spectrometer, scanning electron microscope, spectrophotometer and infrared emissivity tester, and the effects of Er3+ doping on its infrared and laser emissivity were studied. At the same time, the Sn1−xErxO2 (x = 0%, 16%) doping models were constructed based on the first principles of density functional theory, and the related optoelectronic properties such as their energy band structure, density of states, reflectivity and dielectric constant were analyzed, and further explained the mechanism of Er3+ doping on SnO2 infrared emissivity and laser absorption from the point of electronic structure. The results showed that after calcination at 600°C, single rutile type SnO2 was formed, and the crystal structure was not changed by doping Er3+. The calcined products showed good fiber morphology, and the average fiber diameter was 402 nm. The infrared emissivity and resistivity of the samples both decreased first and then increased with the increase of Er3+ doping amount. When x = 16%, the infrared emissivity of the sample was at least 0.71; and Er3+ doping can effectively reduce the reflectivity of SnO2 at 1.06 μm and 1.55 μm, when x = 16%, its reflectivity at 1.06 μm and 1.55 μm are 50.5% and 40%, respectively, when x = 24%, the reflectivity at 1.06 μm and 1.55 μm wavelengths are 47.3% and 42.1%, respectively. At the same time, the change of carrier concentration and electron transition before and after Er3+ doping were described by firstprinciple calculation, and the regulation mechanism of infrared emissivity and laser reflectivity was explained. This study provides a certain experimental and theoretical basis for the development of a single-type, light-weight and easily prepared infrared and laser compatible-stealth material.

Assessing the Impact of Defects on Lead‐Free Perovskite‐Inspired Photovoltaics via Photoinduced Current Transient Spectroscopy

AbstractThe formidable rise of lead‐halide perovskite photovoltaics has energized the search for lead‐free perovskite‐inspired materials (PIMs) with related optoelectronic properties but free from toxicity limitations. The photovoltaic performance of PIMs closely depends on their defect tolerance. However, a comprehensive experimental characterization of their defect‐level parameters—concentration, energy depth, and capture cross‐section—has not been pursued to date, hindering the rational development of defect‐tolerant PIMs. While mainstream, capacitance‐based techniques for defect‐level characterization have sparked controversy in lead‐halide perovskite research, their use on PIMs is also problematic due to their typical near‐intrinsic character. This study demonstrates on four representative PIMs (Cs3Sb2I9, Rb3Sb2I9, BiOI, and AgBiI4) for which Photoinduced Current Transient Spectroscopy (PICTS) offers a facile, widely applicable route to the defect‐level characterization of PIMs embedded within solar cells. Going beyond the ambiguities of the current discussion of defect tolerance, a methodology is also presented to quantitatively assess the defect tolerance of PIMs in photovoltaics based on their experimental defect‐level parameters. Finally, PICTS applied to PIM photovoltaics is revealed to be ultimately sensitive to defect‐level concentrations <1 ppb. Therefore, this study provides a versatile platform for the defect‐level characterization of PIMs and related absorbers, which can catalyze the development of green, high‐performance photovoltaics.

Light Industry Technology of Chiral Perovskite Nanomaterials Construction and Photoelectric Properties

Perovskite nanomaterials have become a new research hotspot due to the many novel physical properties of quantum effects and have good application prospects in the field of optoelectronics. Among them, the realization of controllable fabrication of perovskite nanomaterials is the basis of performance studies and applications and is also a difficult point. Reducing production costs to improve manufacturing methods, further improve product controllability, promote advantages, or improve disadvantages will be very important for further application of perovskite nanomaterials. Therefore, this paper studies the construction of titanium ore nanomaterials by designing a novel preparation process and, at the same time, analyzes the related optoelectronic properties of the obtained materials. In this paper, a triangular PbI2 nanosheet having a uniform and controllable shape and size was successfully fabricated by physical vapor deposition through the introduction of a limited space, and related characterization was performed to show uniform controllability and high crystallinity. Using PbI2 nanosheets as the substrate, MAPbI3 nanosheets were further prepared and related characterizations proved that the obtained nanosheets had high crystallinity and excellent optical properties. The experiment proves that the peak position of the fluorescence spectrum obtained by Gaussian fitting is 800 nm and the half‐peak width is about 45 nm. At the same time, MAPbI3 exhibits strong light absorption characteristics when the wavelength is less than 800 nm. This shows that this enclosed space deposition method can improve the uniformity and controllability of PbI2 and MAPbI3 nanosheet fabrication, which provides the basis for further research on MAPbI3 nanomaterials and references to the controllable growth of other nanomaterials.

Methodologies in Spectral Tuning of DSSC Chromophores through Rational Design and Chemical-Structure Engineering.

The investigation of new photosensitizers for Grätzel-type organic dye-sensitized solar cells (DSSCs) remains a topic of interest for researchers of alternative solar cell materials. Over the past 20 years, considerable and increasing research efforts have been devoted to the design and synthesis of new materials, based on “donor, π-conjugated bridge, acceptor” (D–π–A) organic dye photosensitizers. In this paper, the computational chemistry methods are outlined and the design of organic sensitizers (compounds, dyes) is discussed. With reference to recent literature reports, rational molecular design is demonstrated as an effective process to study structure–property relationships. Examples from established organic dye sensitizer structures, such as TA-St-CA, Carbz-PAHTDDT (S9), and metalloporphyrin (PZn-EDOT), are used as reference structures for an examination of this concept applied to generate systematically modified structural derivatives and hence new photosensitizers (i.e., dyes). Using computer-aided rational design (CARD), the in silico design of new chromophores targeted an improvement in spectral properties via the tuning of electronic structures by substitution of molecular fragments, as evaluated by the calculation of absorption profiles. This mini review provides important rational design strategies for engineering new organic light-absorbing compounds towards improved spectral absorption and related optoelectronic properties of chromophores for photovoltaic applications, including the dye-sensitized solar cell (DSSC).

Self-Healing Originated van der Waals Homojunctions with Strong Interlayer Coupling for High-Performance Photodiodes.

The dangling-bond-free surfaces of van der Waals (vdW) materials make it possible to build ultrathin junctions. Fundamentally, the interfacial phenomena and related optoelectronic properties of vdW junctions are modulated by the interlayer coupling effect. However, the weak interlayer coupling of vdW heterostructures limits the interlayer charge transfer efficiency, resulting in low photoresponsivity. Here, a bilayer MoS2 homogeneous junction is constructed by stacking the as-grown onto the self-healed monolayer MoS2. The homojunction barrier of ∼165 meV is obtained by the electronic structure modulation of defect self-healing. This homojunction reveals the stronger interlayer coupling effect in comparison with vdW heterostructures. This ultrastrong interlayer coupling effect is experimentally verified by Raman spectra and angle-resolved photoemission spectroscopy. The ultrafast interlayer charge transfer takes place within ∼447 fs, which is faster than those of most vdW heterostructures. Furthermore, the homojunction photodiode manifests outstanding rectifying behavior with an ideal factor of ∼1.6, perfect air stability over 12 months, and high responsivity of ∼54.6 mA/W. Moreover, the interlayer exciton peak of ∼1.66 eV is found in vdW homojunctions. This work offers an uncommon vdW junction with strong interlayer coupling and perfects the relevance of interlayer coupling and interlayer charge transfer.

Shape-modulated multiple exciton generation and optoelectronic properties in PbSe nanostructures

Multiple exciton generation (MEG) in semiconductor nanostructures is of great interest for the enhancement of related performances in optoelectronic devices and for the shape dependence of conversion efficiency with which absorbed photons are converted into electron-hole pairs. However, theoretical insight into the coupling effects from the size and shape gradient on the MEG and related optoelectronic properties at the atomic level remains unclear. Here, we investigate the MEG and optoelectronic properties in PbSe nanostructures with different morphologies (nanocrystals, nanowires, and nanocones) based on the bond relaxation correlation mechanism, detailed balance principle, and Fermi statistical theory. It is found that size reduction of nanostructures can increase the bandgap, suppress the threshold energy, and enhance the MEG efficiency. Moreover, optimal conversion efficiency of PbSe nanostructures can be achieved by modulating the geometrical parameters.

Amino Acid-Mediated Synthesis of CsPbBr3 Perovskite Nanoplatelets with Tunable Thickness and Optical Properties

Metal halide perovskites (MHPs) have recently attracted considerable attentions due to their remarkable optoelectronic properties. Colloidal synthesis of MHPs provides a versatile route to precisely control their dimensionality and the related optoelectronic properties. Herein, we report on amino acid (Trp)-mediated synthesis of quasi-two-dimensional CsPbBr3 perovskite nanoplatelets (NPLs) with well-controlled and tunable thickness. The number of layers (n) could be finely tuned from 4 to 12 by simply adjusting Trp concentration, leading to gradual red shift of their photoluminescence (PL). This allows us to directly correlate their thickness with the band gap energy in the quantum confinement regime, which is in good agreement with theoretical model. We found that Trp is the only hydrophobic amino acid to promote the formation of 2D CsPbBr3 NPLs. The use of Trp derivatives for CsPbBr3 nanocrystal synthesis indicates that the carboxyl group, amine group, and indole ring of Trp act synergistically on CsPbB...

Precise growth of low-dimensional pyrene·perylene·TCNQ co-crystals and structure–property related optoelectronic properties

A phase-transformation strategy has been developed for the precise growth of charge-transfer (CT) co-crystals with varied stoichiometries.

Assessment of density functional methods for exciton binding energies and related optoelectronic properties

Mean absolute error (MAE) in exciton binding energy (Eb) from 9 DFT methods against benchmark CCSD and EOM-CCSD.

Tunable electrogenerated chemiluminescence from CdSe nanocrystals

Electrochemical behavior and related optoelectronic properties of CdSe nanocrystals (NCs) in aprotic solutions have been investigated. NCs of 2.50 ± 0.50 nm diameter were synthesized using a modified procedure in which the temperatures at the time of Se precursor injection and NC growth were controlled. The electrochemical band gap was found to agree with those determined by UV–vis absorption spectroscopy and by the tunneling current-voltage spectrum in the literature. Electrogenerated chemiluminescence of the NCs with peak maxima at 1.90 eV (red, 653 nm) and 2.55 eV (blue, 486 nm) can be generated and altered by scanning the voltage between –1.60 and –1.80 V and between –2.00 and –2.20 V, respectively. The results demonstrate the potential capability of the NCs for light emission tuned by the applied potential.Key words: CdSe nanocrystals, electrochemistry, electrogenerated chemiluminescence, UV–vis spectroscopy, photoluminescence.

Vapor growth of electrochromic thin films of transition metal oxides

Mixed oxide films of transition metals gain considerable much attention due to their interesting optoelectronic properties. The low temperature chemical vapor growth processing of thin films of mixed W and Mo oxides is presented. The investigation is related to optimization of films structure and the related optoelectronic properties in dependence on the chemical vapor deposition (CVD) process parameters. Their electrochromic behavior and photoelectrode properties were studied.

Visible Electro- and Photoluminescence from Porous Silicon and its Related Optoelectronic Properties

ABSTRACTThe optoelectronic properties of porous Si (PS) are presented in terms of electroluminescence (EL), photoluminescence (PL), photoconduction (PC), and optical absorption. Observations of injection-type EL, efficient PL, band-gap widening, and photosensitivities In the visible region are consistent with the quantum size effect model in PS.