Optoelectronic Performance Research Articles

Enhancing photoluminescence of monolayer MoS2 on h-BN substrate through plasmonic resonance for high-power optoelectronic devices

Abstract Hexagonal boron nitride (h-BN) is an excellent substrate material due to its superb thermal conductivity, excellent thermal stability and smooth surface qualities. In this study, a silicon-based h-BN substrate was prepared using the magnetron sputtering technique. Subsequently, monolayer MoS2 obtained by the CVD method was transferred onto the h-BN substrate. Then, Au-core-Ag-shell nanoparticles with a diameter of 80 nm were prepared by a self-assembly method and uniformly dispersed and spin-coated on the MoS2 surface. Applying a laser with a wavelength of 532 nm can effectively excite the plasma resonance effect of the system. Under the intense thermal effect induced by the high laser power and plasma effect, the h-BN substrate ensures that MoS2 exhibits less red-shift and higher photoluminescence intensity compared with SiO2 substrate due to its excellent thermal conductivity. This means that h-BN substrates are particularly suitable for optoelectronic applications under high laser power environments, and can maintain excellent optoelectronic device performance while effectively curbing overheating to ensure long-term stable device operation.

Advancements and Challenges in Wide‐Bandgap Perovskite Solar Cells: From Single Junction to Tandem Solar Cells

The exceptional optoelectronic performance and cost‐effectiveness of manufacturing have propelled organic–inorganic hybrid perovskite solar cells (PSCs) into the spotlight within the photovoltaic community. Currently, the single‐junction PSCs have achieved a certified power conversion efficiency surpassing 26%, edging closer to the illustrious Shockley–Queisser theoretical limit. To further enhance device performance, researchers are currently directing their attention toward the integration of wide‐bandgap (WBG) perovskites (Eg > 1.60 eV) as top subcells in conjunction with narrow‐bandgap materials, such as perovskite, crystalline silicon, and copper indium gallium selenium, to construct multijunction tandem devices that maximize solar spectral utilization and minimize thermal losses. However, WBG perovskites encounter challenges associated with suboptimal crystal quality, high defect density, and severe phase separation, leading to significant voltage losses and inferior performance. In this regard, extensive research has been conducted, yielding significant findings. This review article summarizes the advancements in composition engineering, additive engineering, and interface engineering of WBG PSCs. Furthermore, the applications of WBG PSCs in various tandem solar cells and their development are discussed. Finally, future prospects for the development of WBG PSCs are outlined.

Defect Passivation Strategies in Two‐Dimensional Organic–Inorganic Hybrid Perovskites for Enhanced Photoelectric Performance

AbstractThe polycrystalline perovskite films treated with solutions inevitably are subjected to high‐density crystal defects, significantly affecting the performance and stability of perovskite‐based photodetectors. In this research, a reasonably designed organic small molecule using piperazine iodide (PI) as an additive is employed to modify the perovskite films. The results indicate that this designed molecule not only improves the crystallinity of the perovskite film but also effectively passivates defects by modifying the local electron density. Consequently, recombination of non‐radiation charges is inhibited, improving the optoelectronic performance and stability of the device. The modified flexible photoelectric device exhibits a responsivity of 3.07 mA W−1 under 405 nm laser illumination. Notably, it maintains a high responsivity even after 7000 bending cycles. Furthermore, generality of the strategy is verified by applying it to various types of two‐dimensional organic–inorganic hybrid perovskite. Additionally, another small molecular amine phthalimide (PTM) is selected as an additive to further verify the universality of this strategy, which reveals that it demonstrates the same passivation as PI. This strategy provides a novel idea for defect passivation of two‐dimensional organic–inorganic hybrid perovskite, signifying a practical application significance for developing flexible wearable devices with optimized performance, perovskite light‐emitting diodes, and solar cells.

Near space detection technology combining van der Waals heterojunction photodetectors with long-range infrared target detection algorithms

To test the target detection accuracy of infrared detectors in practical applications, this study proposes a near space detection (NSD) technology that integrates van der Waals heterojunction photodetectors with long-range infrared target detection algorithms (ITDAs). A van der Waals heterojunction infrared photodetector (MoS2/CdTe) is prepared by combining molybdenum disulfide thin film and cadmium telluride substrate, and depositing gold electrodes on both substrates. A fusion algorithm of spatiotemporal target detection network and local contrast method is proposed for long-distance detection of weak infrared targets, and a near-space infrared detection system is designed. The data showed that the MoS2/CdTe heterojunction photodetector had a detection range of 200–1700 nm and a response of 36.7 mA/W, demonstrating excellent optoelectronic performance. The false alarm rates of the long-distance ITDA were 0.006% and 0.009%, respectively, which are significantly better than the target detection algorithm based on local contrast. In the testing of the near-space infrared detection system, the errors in the shortwave and longwave field of view tests were 2.5% and 5.2%, respectively, and the resolution test errors were 3.6% and 3.7%. The infrared detection system meets the performance standards, has high detection ability and stability, and provides a more effective solution for NSD.

Near‐Unity Green Luminescent and Stable Lead‐Free Cs3Cu2Cl5 Nanocrystals Assisted by MnC2O4 Treatment

AbstractThe toxicity and chemical instability shortcomings of lead halide perovskites are major concerns that continue to motivate the search for next generation alternatives. Copper halides are known to be lead‐free, earth‐abundant, low‐cost, and environmentally friendly, and affordable in optoelectronic performance due to their bright luminescence, tunable emission wavelength, and excellent stability. However, the controlled synthesis of low‐dimensional copper halide nanocrystals (NCs) with near‐unity photoluminescence quantum yield (PLQY) and high stability remains a great challenge. In this work, we report a reasonable optimization approach for the preparation of Cs3Cu2Cl5 NCs by hot‐injection colloidal synthesis technology. Specifically, the Cs3Cu2Cl5 NCs synthesized with MnC2O4 as the defect repair agent exhibited negligible self‐absorption, bright green luminosity with PL emission at about 535 nm and PLQY can be increased from 68.7 % to 100 %. The Cs3Cu2Cl5 NCs shows excellent stability and outstanding optical properties, and is expected to be used as highly efficient green light emitter in high‐efficiency X‐ray scintillator.

Real-time detection of aging status of methylammonium lead iodide perovskite thin films by using terahertz time-domain spectroscopy

The inadequate stability of organic–inorganic hybrid perovskites remains a significant barrier to their widespread commercial application in optoelectronic devices. Aging phenomena profoundly affect the optoelectronic performance of perovskite-based devices. In addition to enhancing perovskite stability, the real-time detection of aging status, aimed at monitoring the aging progression, holds paramount importance for both fundamental research and the commercialization of organic–inorganic hybrid perovskites. In this study, the aging status of perovskite was real-time investigated by using terahertz time-domain spectroscopy. Our analysis consistently revealed a gradual decline in the intensity of the absorption peak at 0.968 THz with increasing perovskite aging. Furthermore, a systematic discussion was conducted on the variations in intensity and position of the terahertz absorption peaks as the perovskite aged. These findings facilitate the real-time assessment of perovskite aging, providing a promising method to expedite the commercialization of perovskite-based optoelectronic devices.Graphical

Adjustable optoelectronic properties of triphenylamine-ethylenedioxythiophene based hybrid electrochromic polymer with different electron-donating substituents

Due to the good optoelectronic properties of triphenylamine (TPA) and its derivatives-based organic conjugated polymers, they have been widely used in various organic electronic devices. They are easy to lose electrons to form stable cationic free radicals with color change under electrochemical oxidation conditions. Therefore, TPA derivatives-based electrochromism materials have attracted the widely attentions of researchers. In this work, a series of TPA derivatives were successfully obtained by Stille coupling reactions, and their basic optical and electrical properties were investigated in detail. Their corresponding polymer films (P(TPA-EDOT), P(PhTPA-EDOT), and P(OCH3TPA-EDOT)) were also prepared on transparent ITO glass by electrodeposition method and their electrochromic properties were further studied. Due to the relatively strong electron donating ability of OCH3– group on the TPA unit, the intramolecular charge transfer peak of OCH3TPA-EDOT is obvious red-shifted and its initial oxidation potential is relatively low, which is beneficial for it to get high-quality electrochromic polymers. Electrochemical analysis shows that all these three polymer films show reversible redox reaction with excellent redox stability. Spectroelectrochemistry shows that all of them have good electrochromic properties and show multi-electrochromic behavior with strong color change. The dynamic study show that all these three polymers have relatively fast switching time (as low as 0.8 s), high coloration efficiency (up to 206.2 C−1 cm2) and obvious optical contrast change. Especially in the near infrared region, the optical contrast is relatively high (P(TPA-EDOT) is 45.3 % at 1100 nm, P(PPhTPA-EDOT) is 53.1 % at 1100 nm, and P(OCH3TPA-EDOT) is 57.2 % at 1100 nm). All these results show that the different substituents on the TPA unit have a certain influence on the resultant monomers’ optoelectronic performances, and they also can adjust the optical band gap of the corresponding polymers with different electrochromic properties.

All-solution preparation of perovskite light-emitting diodes in ambient air through film-forming regulation of light-emitting layers based on dual-additive doping and oxygen plasma treatment

Organic-inorganic hybrid perovskites are promising for optoelectronics owing to their high color purity, tunable bandgaps, and low nonradiative recombination rates. However, challenges such as rough surfaces and poor film-forming properties constrain the optoelectronic performance of light-emitting devices. Herein, the PEDOT:PSS film treated by oxygen plasma serves as the hole transport layer, while the formation of perovskite films is optimized by dual-additive doping of PEO and TPBi in ambient air. The results show that the PEDOT:PSS films with PSSH-rich after oxygen plasma treatment provide more nucleation sites, favoring the formation of the perovskite film. Meanwhile, the dual-additive prompts to form a dense and uniform film as well. The intrinsic mechanisms involve PEO as a binder to fill grain gaps and improve water-oxygen stability in the perovskite film, while TPBi acts as a passivator to stimulate uniform nucleation and dense crystallization, improving the grain coverage of the light-emitting layer. Under atmospheric conditions, all-solution processed perovskite devices reach a maximum luminance of 810.4 cd m−2 and a maximum current efficiency of 0.437 cd A−1. This work highlights the significance of using oxygen plasma treatment and additives to improve the performance of perovskite films and achieve superior PeLEDs.

Effect of partial cation substitution on optoelectronic properties and ion diffusion behavior of inorganic lead halide perovskite: A theoretical investigation

Cation substitution is a widely utilized approach for tailoring the properties of lead halide perovskites. A comprehensive understanding of the impact of various cation substitutions on optoelectronic properties and ion diffusion behavior is crucial for enhancing the performance of halide perovskite materials. In this study, we constructed various double halide perovskites by cation substitution and investigated their optoelectronic properties and ion diffusion behavior through first-principles calculations. Our findings reveal that the A-site substitution with alkali cation Rb does not significantly influence the optoelectronic properties of lead halide perovskites. However, it will boost the halide migration due to the enlarged migration bottleneck. The B-site substitution with alkali earth element Sr significantly suppresses the halide migration; while the material will be no longer suitable for visible light absorption due to the enlarged bandgap. The substitution of Pb with d-orbital fulfilled Zn can also suppress the halide migration, but it will give rise to an indirect bandgap and hence affect the optoelectronic performance. The substitution of Pb with Sn can enhance both the thermostability and optoelectronic performance owing to the smaller ionic radius and similar ns2-containing electronic configuration. The increased migration barrier indicates that ion diffusion is also inhibited in double perovskite Cs2SnPbI6. Our results imply that the optoelectronic properties can be further optimized by tuning the ratio of Sn/Pb or the thickness of the perovskite layer in photovoltaic device. These results would be useful guide for the development of novel lead-less optoelectronic perovskite materials.

Tuning of optoelectronic performance of SrTiO3 by surface termination and thickness

The outstanding optical and electrical properties make ternary oxides highly suitable for advanced optoelectronic applications comparing to the traditional silicon-based materials and heterostructures. SrTiO3 (STO), a pivotal perovskite oxide with a direct energy band gap of 3.2 eV, exhibits significant promise in ultraviolet (UV) photodetection. However, the photovoltaic performance of homoepitaxial STO has long been neglected. In this study, we investigated the optoelectronic characteristics of STO by manipulating the crucial factors of surface termination and thickness using oxide molecular beam epitaxy (oxide MBE). We achieved an exceptional charge carrier mobility of 56.5975 cm2 V-1s−1, along with an impressive ON/OFF ratio of 6000 % and a specific detectivity (D*) of 2.95 × 109 Jones (cm Hz1/2 W−1) under near-UV irradiation at room temperature. We observed a thickness-dependent semiconductor-to-metal transition with a critical thickness of 3.5 u.c. STO. The metallic STO displayed an extremely high mobility exceeding 105 cm2 V−1 s−1, accompanied by a substantial MR value exceeding 1000 % at 3 K. Furthermore, the thickness-dependent Hall effect and photoluminescence (PL) indicated that oxygen defects may govern the semiconducting/metallic behavior of STO. This study illustrates the optoelectrical capabilities of homoepitaxial STO, paving the way for advanced and high-performance photodetection in intricate optical materials and devices through homoepitaxy.

Colloidal Quantum Dot‐Based Near and Shortwave Infrared Light Emitters: Recent Developments and Application Prospects

AbstractSolution‐processed quantum dot‐based near and short‐wave infrared light emitters have witnessed substantial developments in recent years. A variety of colloidal quantum dots (CQDs)‐based light emitters, including light‐emitting diodes, optical down‐converters, and emitters showing amplified spontaneous emission, lasing in the near and short‐wave infrared region, are demonstrated over the years. The progress in chemical synthesis of CQDs, development of novel CQDs, better understanding of the surface properties, chemical treatments to improve the optoelectronic properties, and suitable device engineering led to tremendous advances in the light emission performance in the near and short‐wave infrared region. A broad investigation is done into various CQD materials to achieve efficient near‐infrared light emitters. This review gives a detailed account of the advancement of the CQD‐based near and short‐wave infrared light emitters, strategies to improve the optoelectronic performance, controlling optical properties, demonstrated applications, the challenges that need to be tackled for further development, and future research direction.

Unraveling lead-free Fr-based perovskites FrQCl3 (Q = Ca, Sr) and their pressure induced physical properties: DFT analysis for advancing optoelectronic performance

A comprehensive study of structural, electronic, elastic, and optical properties of the cubic FrQCl3 (Q = Ca, Sr) perovskite under pressure 0 − 105 GPa has been considered. Interestingly, FrCaCl3 experiences a shift from an indirect to a direct bandgap material at 12 GPa, while FrSrCl3 undergoes the same shift at 10 GPa, rendering these materials more advantageous for application in optoelectronic devices. As pressure rises, the electronic density of states increases near the Fermi level by shifting valence band electrons upward. This leads to a reduction in the bandgap and a shift of the bandgap from the ultraviolet to the visible region. The examination of mechanical properties indicates that FrQCl3 (Q = Ca, Sr) perovskite exhibits significant potential for uses requiring a combination of anisotropic, and ductile behavior. Optical property analysis reveals that with an increase in hydrostatic pressure, dielectric constant's peak of both material shift towards lower photon energy area.

Rational synthesis of core/shell heterostructured quantum dots for improved self-powered photodetection performance enabled by energy band engineering

Colloidal quantum dots (CQDs), especially core-shell QDs, have attracted dramatic interests as emerging materials in optoelectronic devices due to their size tuneable band-gap, high absorption coefficient, facile and low-cost synthesis routing, etc. However, the precise design of core/shell band engineering along with charge carrier transfer efficiency are still challenging, inevitably impacting the performance of optoelectronic devices. Herein, three different types of CdSe/CdS core-shell heterostructured QDs have been obtained via a proposed synthesis strategy of adjusting the core size but fixing the shell thickness. The performance of the core-shell QDs based self-powered photodetectors can be efficiently regulated by the optimization of synthesis strategy with the design of energy band alignment. Compared to the quasi type-II and the type-I QDs devices, the Ilight/Idark ratio of type-II heterostructure based photodetector is increased by ∼2 and ∼5 orders of magnitude, respectively. The champion device exhibits extraordinary optoelectronic performance in terms of ultrahigh light-to-dark current ratio of 105, photoresponsivity of 10.64 mA/W, at bias of 0 V, respectively. The charge carrier dynamics and transfer mechanisms of the QDs were further investigated, revealing the improved carrier separation and transportation efficiency induced by a strong build-in electric field in type-II CdSe/CdS core-shell heterostructure. This work provides a new strategy for the next-generation self-powered QDs optoelectronics enabled by the proposed synthesis approach along with the design of energy band alignment.

Quantification of Two-Dimensional Interfaces: Quality of Heterostructures and What Is Inside a Nanobubble.

Trapped materials at the interfaces of two-dimensional heterostructures (HS) lead to reduced coupling between the layers, resulting in degraded optoelectronic performance and device variability. Further, nanobubbles can form at the interface during transfer or after annealing. The question of what is inside a nanobubble, i.e., the trapped material, remains unanswered, limiting the studies and applications of these nanobubble systems. In this work, we report two key advances. First, we quantify the interface quality using RAW format optical imaging (unprocessed image data) and distinguish between ideal and non-ideal interfaces. The HS/substrate ratio value is calculated using a transfer matrix model and is able to detect the presence of trapped layers. The second key advance is the identification of water as the trapped material inside a nanobubble. To the best of our knowledge, this is the first study to show that optical imaging alone can quantify interface quality and find the type of trapped material inside spontaneously formed nanobubbles. We also define a quality index parameter to quantify the interface quality of HS. Quantitative measurement of the interface will help answer the question whether annealing is necessary during HS preparation and will enable creation of complex HS with small twist angles. Identification of the trapped materials will pave the way toward using nanobubbles for optical and engineering applications.

Organic-Inorganic Rubrene/WS2 Heterostructure for Broadband Detection and Polarization Imaging.

Organic single crystals exhibit improved carrier mobility, longer exciton diffusion length, anisotropic charge transport, and unique linear dichroism, while its high exciton binding energy seriously limits the free-carrier generation and photoelectric conversion efficiency. Layered van der Waals heterostructures, which integrate organic crystals with high mobility two-dimensional (2D) inorganic semiconductors, are promising for promoting exciton dissociation and boosting sensitivity by utilizing the interfacial potential and photogating effect. In this work, organic single-crystal rubrene is integrated with a few-layer WS2 to design the high-performance photodetector. The device exhibits an excellent responsivity of 1000 A W-1, and a fast speed of 180 μs, which is far superior to the individual WS2 device. Equally importantly, this device provides excellent polarization detection performance by virtue of the anisotropic properties of rubrene, and the dichroic ratios are 1.56, 1.5, and 1.7 for 375, 405, and 658 nm irradiation, respectively. Finally, several high-resolution single-pixel broadband polarization imaging was demonstrated. Our work shows that organic-inorganic heterostructure is an essential candidate for improving optoelectronics performance and has potential for polarization imaging.

Optoelectronic performance of Jatropha oil-derived poly(ethyl carbamate) gel polymer electrolyte as quasi-solid-state solution for photoelectrochemical cells

Optoelectronic performance of Jatropha oil-derived poly(ethyl carbamate) gel polymer electrolyte as quasi-solid-state solution for photoelectrochemical cells

Extending the Charge Carrier Recombination Lifetime by Octahedral Rotations in Ruddlesden-Popper Ba3Zr2S7 Perovskites.

Intentional distortions of [BX6] octahedra within perovskite structures have been recognized as a potent strategy for precise band gap adjustments and optimization of their photovoltaic properties, yet information regarding charge carrier dynamics linked to octahedral distortion under ambient conditions for chalcogenide perovskites remains limited. In this study, we utilize ab initio nonadiabatic molecular dynamics to explore the dynamics of photogenerated carriers in a representative two-dimensional Ba3Zr2S7 material in the Ruddlesden-Popper phase. The theoretical results highlight the influence of octahedral rotation on the materials' stability and carrier recombination lifetime of the system. Specifically, the octahedrally rotating P42/mnm phase exhibits a prolonged nonradiative carrier recombination lifetime attributed to the stabilized electron-phonon coupling. These findings offer valuable insights into the fundamental physical characteristics of imposed octahedral distortion and its potential for optimizing the optoelectronic performance of 2D Ruddlesden-Popper Ba-Zr-S chalcogenide materials.

Concentric hollow multi-hexagonal platelets from a small molecule

The creation of well-defined hollow two-dimensional structures from small organic molecules, particularly those with controlled widths and numbers of segments, remains a formidable challenge. Here we report the fabrication of the well-defined concentric hollow two-dimensional platelets with programmable widths and numbers of segments through constructing a concentric multiblock two-dimensional precursor followed by post-processing. The fabrication of concentric multi-hexagons two-dimensional platelets is realized by the alternative heteroepitaxial growth of two donor-acceptor molecules. Upon ultraviolet irradiation, one of the two donor-acceptor molecules can be selectively oxidized by singlet oxygen generated during the process, and the oxidized product becomes more soluble due to increased polarity. This allows for selective removal of the oxidized segments simply by solvent dissolution, yielding hollow multiblock two-dimensional structures. The hollow two-dimensional platelets can be utilized as templates to lithograph complex electrodes with precisely controlled gap sizes, thereby offering a platform for examining the optoelectronic performance of functional materials.

Tin doping modulates electron-hole recombination in Dion-Jacobson phase 2D hybrid perovskite

To obtain less-toxic and optimal-band-gap perovskite materials, tin (Sn)-lead (Pb) hybrid technology comes into the sight of researchers. The Sn–Pb ratio primarily affects the electronic band structure, conductivity, and carrier transport, which are essential for optoelectronic performance. While most reports are about 3D materials, there has been little coverage of 2D Sn–Pb perovskites which exhibiting improved stability. In this paper, the e-h recombination dynamics in Dion-Jacobson Phase 2D Sn–Pb perovskites are studied using time-dependent ab initio nonadiabatic molecular dynamics (NAMD) simulation. It is found that Sn doping plays a significant role in narrowing the band-gap of 2D perovskites and localizing the charge distribution. Only a small amount of Sn doping can minimize NA coupling and shorten decoherence time of frontier orbitals simultaneously, then leading to longer charge recombination time. NAMD simulations reveal the optimal Sn ratio (25 mol%) and provide an effective way to design high-performance 2D perovskite materials.

Piezotronically tuned photosensitivity in ZnO varistor-type interface devices

The study of piezotronic and piezo-phototronic features in semiconducting piezoelectrics has gained considerable attention for optimizing electronic and optoelectronic device performance. In this study, we explore the photocurrent response within a ZnO varistor-type interface device and examine its UV photosensitivity enhancement through piezo-phototronic modulation of the potential barriers at grain boundaries. Doped ZnO bicrystals were synthesized using the epitaxial solid-state transformation method with polarization vectors perpendicular to the interface. The vectors can be directed both into and out of the interfaces depending on the crystallographic orientation of the crystals designated as (0001̅)|(0001̅) and (0001)|(0001) interfaces, respectively. These varistor-type boundaries demonstrate an exceptional photoelectric response to UV photons. Furthermore, our results indicate that the photoresponsivity of bicrystals with (0001)|0001 crystallographic orientation can be further enhanced under piezo-phototronic influence. Application of compressive stress of 100 MPa not only increased photocurrent formation by 1000 % but also boosted photosensitivity by 1400 %, attributed to the elevated double Schottky barrier (DSB) height at the interface resulting from mechanical loading on the bicrystal. Our findings highlight the significant role of piezoelectrically tuned potential barriers at grain boundaries in enhancing the separation and extraction of photogenerated excitons for photocurrent formation. This study introduces the engineered varistor-type interface as a promising candidate for future optoelectronic devices and contributes to our understanding of the piezo-phototronic concept in semiconductor-semiconductor interface devices.