Photoactive Layer Research Articles

Numerical study of copper antimony sulphide (CuSbS2) solar cell by SCAPS-1D

Copper antimony sulphide thin films are promising, less toxic, and more absorbent material in the world, and they would be good to be applied in photovoltaic energy production. To better operations of copper antimony sulphide (CuSbS2) photovoltaic cells, this paper uses a solar cell capacitance simulator (SCAPS-1D) to simulate and analyze photovoltaic properties. This article examines different thicknesses of fluorine-doped tin oxide (FTO), cadmium sulphide (CdS), carbon (C), and CuSbS2, as well as the defect and dopant concentration in the CuSbS2 photoactive layer of the photovoltaic cell structure glass/FTO/n-CdS/p-CuSbS2/C/Au. Optimum thicknesses of CuSbS2 is 300 nm, carbon hole transport layer (HTL) is 50 nm, and for n-CdS electron transport layer (ETL) is 100 nm, giving open circuit Voltage (Voc) of 0.9389 V, short circuit current density (Jsc) of 28.32 mA/cm2, fill factor (FF) of 60.8% and solar cell efficiency of 16.17%. The increase in defects causes a decrease of carrier lifetime resulting in to decrease in diffusion length and the optimum absorber layer doping concentration was found to be 1018 cm−3.

Progress and Application of Halide Perovskite Materials for Solar Cells and Light Emitting Devices.

Halide perovskite materials have attracted worldwide attention in the photovoltaic area due to the rapid improvement in efficiency, from less than 4% in 2009 to 26.1% in 2023 with only a nanometer lever photo-active layer. Meanwhile, this nova star found applications in many other areas, such as light emitting, sensor, etc. This review started with the fundamentals of physics and chemistry behind the excellent performance of halide perovskite materials for photovoltaic/light emitting and the methods for preparing them. Then, it described the basic principles for solar cells and light emitting devices. It summarized the strategies including nanotechnology to improve the performance and the application of halide perovskite materials in these two areas: from structure-property relation to how each component in the devices affects the overall performance. Moreover, this review listed the challenges for the future applications of halide perovskite materials.

Dithienopyran-based narrow-bandgap donor polymers: Unveiling the potential for semitransparent organic solar cells with enhanced NIR absorption

Semitransparent organic solar cells (ST-OSCs) have recently received considerable attention in the field of photovoltaics owing to their great potential in applications such as building-integrated photovoltaics, self-powered greenhouses, and vehicle coatings. Because the near-infrared (NIR) region is an invisible region whose photon content is higher than that of the visible region, it is preferable to apply photoactive materials with narrow bandgaps in ST-OSCs. Tremendous efforts have been made to develop narrow-bandgap non-fullerene acceptors, however, donor polymers with NIR absorption ability for efficient ST-OSCs have rarely been reported. In this study, two novel narrow-bandgap donor polymers, PDTP-TBT and PDTTP-TBT, are designed and synthesized. Both polymers exhibit strong NIR absorption and high transmittance in the visible region, suggesting their potential for use in ST-OSCs. An opaque OSC with a PDTTP-TBT-based photoactive layer achieves a higher power conversion efficiency (PCE) of 8.87% than a PDTP-TBT-based OSC (PCE of 3.65%) due to its better charge transport characteristics. Furthermore, an ST-OSC using PDTTP-TBT-based blend film exhibits a PCE of 6.72%, average visible transmittance of 43.9%, and light utilization efficiency of 2.95%.

Rational molecular engineering towards efficient heterojunction solar cells based on organic molecular acceptors

The selection of photoactive layer materials for organic solar cells (OSCs) is essential for the photoelectric conversion process. It is well known that chlorophyll is an abundant pigment in nature and is extremely valuable for photosynthesis. However, there is little research on how to improve the efficiency of chlorophyll-based OSCs by matching chlorophyll derivatives with excellent non-fullerene acceptors to form heterojunctions. Therefore in this study we utilize a chlorophyll derivative, Ce6Me3, as a donor material and investigate the performance of its heterojunction with acceptor materials. Through density functional theory, the photoelectric performances of acceptors, including the fullerene derivative PC71BM and the terminal halogenated non-fullerene DTBCIC series, are compared in detail. It is found that DTBCIC-Cl has better planarity, light absorption, electron affinity, charge reorganization energy and charge mobility than others. Ce6Me3 has good energy level matching and absorption spectral complementarity with the investigated acceptor molecules and also shows good electron donor properties. Furthermore, the designed Ce6Me3/DTBCIC interfaces have improved charge separation and reorganization rates (K CS/K CR) compared with the Ce6Me3/PC71BM interface. This research provides a theoretical basis for the design of photoactive layer materials for chlorophyll-based OSCs.

Strain‐Induced α‐Phase Stabilization for Low Dark Current FAPI‐Based Photodetectors

AbstractFormamidinium lead iodide (FAPbI3) has gained considerable interest as a promising photoactive layer for optoelectronic devices due to its broad spectrum of light absorption and increased thermal stability when compared to its conventional methylammonium counterpart (MAPbI3). Recent developments in substituting formamidinium (FA) with smaller Cs cations have further accelerated its growth in the photovoltaic (PV) community by enhancing phase stability and power conversion efficiency (PCE). However, only a few studies are reported on perovskite photodetectors (PPDs). Here, the influence of Cs incorporation is investigated on PD performance in the CsXFA1‐XPbI3 system (X = 0–0.25). Finding that the partial substitution of FA with Cs cations alleviates lattice strain by increasing crystallinity and inducing a well‐ordered surface morphology with vertical crystallographic orientation, which suppresses non‐radiative recombination mechanisms. Such improved physicochemical properties of the mixed‐cation perovskite light absorbers can improve the PD performance by reducing the dark and noise current to values as low as 3.3 × 10−9 A cm−2 and 6.1 × 1011 A Hz−1/2, thereby enabling PPDs with a faster photoresponse and greater sensitivity, which holds great promise for future optoelectronics applications.

An A-D-A'-D-A-Type Narrow Bandgap Electron Acceptor Based on Selenophene-Flanked Diketopyrrolopyrrole for Sensitive Near-Infrared Photodetection.

Near-infrared organic photodetectors possess great application potential in night vision, optical communication, and image sensing, but their development is limited by the lack of narrow bandgap organic semiconductors. A-D-A'-D-A-type molecules, featuring multiple intramolecular charge transfer effects, offer a robust framework for achieving near-infrared light absorption. Herein, we report a novel A-D-A'-D-A-type narrow bandgap electron acceptor named DPPSe-4Cl, which incorporates a selenophene-flanked diketopyrrolopyrrole (Se-DPP) unit as its central A' component. This molecule demonstrates exceptional near-infrared absorption properties with an absorption onset reaching 1120 nm and a low optical bandgap of 1.11 eV, owing to the strong electron-withdrawing ability and quinoidal resonance effect induced by the Se-DPP unit. By implementing a doping compensation strategy assisted by Y6 to reduce the trap density in the photoactive layer, the optimized organic photodetector based on DPPSe-4Cl exhibited efficient spectral response and remarkable sensitivity in the range of 300-1100 nm. Particularly, a specific detectivity surpassing 1012 Jones in the wavelength range of 410-1030 nm is achieved. This work offers a promising approach for developing highly sensitive visible to near-infrared broadband photodetection technology using organic semiconductors.

Controllable Exciton Diffusion Length and Ultrafast Charge Generation in Ternary Organic Solar Cells

Comprehensive SummaryCharge generation, a critical process in the operation of organic solar cell (OSC), requires thorough investigation in an ultrafast perspective. This work demonstrates that the utilization of alloy model for the non‐fullerene acceptor (NFA) component can regulate the crystallization properties of active layer films, which in turn affects exciton diffusion and hole transfer (HT), ultimately influencing the charge generation process. By incorporating BTP‐eC7 as a third component, without expanding absorption range or changing molecular energy levels but regulating the ultrafast exciton diffusion and HT processes, the power conversion efficiency (PCE) of the optimized PM6:BTP‐eC9:BTP‐eC7 based ternary OSC is improved from 17.30% to 17.83%, primarily due to the enhancement of short‐circuit current density (JSC). Additionally, the introduction of BTP‐eC7 also reduces the trap state density in the photoactive layer which helps to reduce the loss of JSC. This study introduces a novel approach for employing ternary alloy models by incorporating dual acceptors with similar structures, and elucidates the underlying mechanism of charge generation and JSC in ternary OSCs.

Influence of deposition temperature and hydrogen on sustainable and transfer-free graphene transparent electrode for organic solar cells

The transfer-free graphene transparent conducting electrode (TCE) is a promising alternative to indium tin oxide (ITO) for organic solar cells (OSCs). In the present work, a comprehensive investigation on how deposition temperature and H2 flow rates affect the growth, structural, optical, and electrical properties of graphene produced by RF plasma enhanced chemical vapor deposition using sustainable sources was conducted. Inverted-geometry OSCs with P3HT: PCBM photoactive layer were fabricated on transfer-free graphene TCEs developed under different conditions. Moreover, the coupling of silver nanowires (AgNWs) with different graphene films was studied for hybrid graphene-AgNWs TCEs for OSCs. Devices based on graphene TCEs prepared at low or zero H2 flow have shown better performances than those at high flow of H2. Similarly, graphene TCEs prepared at high temperature (>700 °C, on quartz) led to a deteriorated device performance due to the highly increased growth of vertically oriented graphene nanosheets, which dramatically reduced film transmittance and increased surface roughness. The present work provides solid understanding of the growth mechanism of RF-PECVD graphene on glass from a sustainable carbon source. More importantly, the sustainable, ecofriendly, cost- and time-effective production of scalable transfer-free graphene TCEs for OSCs is optimized which paves the way towards ITO-free optoelectronics.

Introducing ZnMgO quantum dots to enhance optoelectrical characteristics of organic photovoltaics via light downconversion

In this study, we developed organic photovoltaics (OPVs) with a photoactive layer based on the bulk heterojunction structure of the high-performance polymer PM6 and nonfullerene acceptor BTP-eC9. Zinc magnesium oxide (ZnMgO) quantum dots (QDs) were introduced into a zinc oxide sol–gel solution as the electron transport layer. The ZnMgO QDs absorb ultraviolet (UV) light and emit visible light (400–700 nm). The absorption area and external quantum efficiency of the fabricated OPV device were enhanced by converting UV light into visible light. Accordingly, the short-circuit current density and fill factor of the OPVs increased from 24.8 to 25.3 mA cm−2 and from 74.0 % to 74.8 %, respectively, and as a result, the power conversion efficiency of the OPVs increased from 15.1 % to 15.7 %. The absorption and photoluminescence emission and the particle size of the synthesized ZnMgO QDs were determined using UV–visible spectroscopy, photoluminescence spectroscopy, and high-resolution transmission electron microscopy.

Ultrasensitive Dual-Mode Visual/Photoelectrochemical Bioassay for Antibiotic Resistance Genes through Incorporating Rolling Circle Amplicons into a Tailored Nanoassembly.

As emerging contaminants in the environment, antibiotic resistance genes (ARGs) have aroused a global health crisis and posed a serious threat to ecological safety and human health. Thus, efficient and accurate onsite detection of ARGs is crucial for environmental surveillance. Here, we presented a colorimetric-photoelectrochemical (PEC) dual-mode bioassay for simultaneous detection of multiple ARGs by smartly incorporating rolling circle amplification (RCA) into a stimuli-responsive DNA nanoassembly, using the tetracycline resistance genes tetA and tetC as models. The tailored DNA nanoassembly containing RCA amplicons hybridized with specific signal probes: CuO nanoflowers-anchored signal DNA1 and HgO nanoparticles-anchored signal DNA2, respectively. Upon exposure to an acidic stimulus, numerous Cu2+ and Hg2+ were released, serving as the reporting agent of colorimetric/PEC dual-mode assay. The released Cu2+ and Hg2+ induced localized surface plasmon resonance shifts in Au nanorods and triangular Ag nanoplates through an etching process, respectively, enabling visual analysis of ARGs with distinguishing color changes. Meanwhile, numerous Cu2+ and Hg2+ triggered the amplified PEC variations via reacting with the photoactive layers of CuS/CdS and ZnS, respectively. Thus, a rapid and ultrasensitive colorimetric/PEC dual-mode detection of multiple ARGs was achieved with the detection limit down to 17.2 aM. Furthermore, such dual-mode bioassay could discriminate single-base mismatch and successfully determine ARGs in E. coli plasmids and sludge samples, holding great promise for point-of-care genetic diagnostics.

A halide perovskite based ternary heterojunction with multi-shell hollow structure for stable and efficient artificial photosynthesis

Low-cost halide perovskite materials hold great promise as photocatalysts for CO2 reduction. However, their inferior water-tolerance will lead to a substantial decline in activity during prolonged photocatalytic CO2 reduction with water as the electron source. Herein, we integrate a lead-free halide perovskite Cs3Bi2I9 as photoactive layer with TiO2 as water oxidation catalyst and g-C3N4 as CO2 reduction catalyst to construct a ternary heterojunction (TiO2/Cs3Bi2I9/g-C3N4) with a multi-shell hollow structure. The formation of heterojunction endows TiO2/Cs3Bi2I9/g-C3N4 composite with enhanced photocatalytic activity for CO2 reduction due to the improved photogenerated carrier separation. TiO2/Cs3Bi2I9/g-C3N4 achieves a CO yield of 120.6 μmol g−1 h−1 for photocatalytic CO2 reduction, which is 3.1 times higher than that of individual Cs3Bi2I9. More importantly, benefitting from the double-sided protection of g-C3N4 and TiO2, the photocatalytic CO2 reduction activity of TiO2/Cs3Bi2I9/g-C3N4 remains undiminished even over 100 h of continuous light irradiation, demonstrating significantly improved stability in water-contained reaction system.

Cover Picture: Molecular Structural Descriptor‐Assisted Machine Learning for Organic Photovoltaics with Perylenediimide Acceptors (BKCS 1/2024) Gyu‐Hee Kim, Keonho Yoon, Chihyung Lee, Minwoo Nam, Doo‐Hyun Ko

The cover picture illustrates the artificial intelligence model that predicts the performance of organic photovoltaics. This model predicts how organic photovoltaics will perform under 1 sun AM 1.5 G illumination by using only the molecular structure of the organic semiconductors within the bulk heterojunction photoactive layer. The organic semiconductors of the target organic photovoltaics comprise polymer donors and bay‐position‐linked diperylenediimide acceptors. More details are available in the article Gyu‐Hee Kim, Keonho Yoon, Chihyung Lee, Minwoo Nam, Doo‐Hyun Koimage

Semitransparent Organic Photovoltaic Devices: Interface/Bulk Properties and Stability Issues

In the present work, an insight on the morpho/structural properties of semitransparent organic devices for buildings’ integrated photovoltaics is presented, and issues related to interface and bulk stability are addressed. The organic photovoltaic (OPV) cells under investigation are characterized by a blend of PM6:Y6 as a photo-active layer, a ZnO ETL (electron transporting layer), a HTL (hole transporting layer) of HTL-X and a transparent electrode composed by Ag nanowires (AgNWs). The devices’ active nanomaterials, processed as thin films, and their mutual nanoscale interfaces are investigated by a combination of in situ Energy Dispersive X-ray Reflectometry (EDXR) and ex situ Atomic Force Microscopy (AFM), X-ray Diffraction (XRD) and micro-Raman spectroscopy. In order to discriminate among diverse concomitant aging pathways potentially occurring upon working conditions, the effects of different stress factors were investigated: light and temperature. Evidence is gained of an essential structural stability, although an increased roughness at the ZnO/PM6:Y6 interface is deduced by EDXR measurements. On the contrary, an overall stability of the system subjected to thermal stress in the dark was observed, which is a clear indication of the photo-induced origin of the observed degradation phenomenon. Micro-Raman spectroscopy brings light on the origin of such effect, evidencing a photo-oxidation process of the active material in the device, using hygroscopic organic HTL, during continuous illumination in ambient moisture conditions. The process may be also triggered by a photocatalytic role of the ZnO layer. Therefore, an alternative configuration is proposed, where the hygroscopic HTL-X is replaced by the inorganic compound MoOx. The results show that such alternative configuration is stable under light stress (solar simulator), suggesting that the use of Molybdenum Oxide, limiting the photo-oxidation of the bulk PM6:Y6 active material, can prevent the cell from degradation.

Characterizing the Thickness Distribution of Donor and Acceptor in Organic Photovoltaics via Quasi‐Monochromatic Light Transmittance

AbstractThe performance of organic solar cells is sensitive to the film thickness and the uniformity of the donor and acceptor distribution in the photoactive layer. Especially, in the quasi‐planar heterojunction fabricated by layer‐by‐layer process, the donor and acceptor materials may be non‐homogeneously distributed across the entire photoactive layer. Visualization of the spatial distributions of donor and acceptor components sheds light on the relationship between nanostructures and device performances. Based on the distinct infrared absorption characteristics of the organic donor and acceptor, a quasi‐monochromatic light transmittance (QMLT) technique is proposed to quantify the donor and/or acceptor thickness in the photoactive layer blend across the entire device area with nanometer precision. The variation in thickness of donor and acceptor can be clearly and separately revealed. Accordingly, the impacts of spin coating techniques (such as dynamic or static dispensing, and on‐center or off‐center spin coating), as well as solvent choices, on film morphology and device performance can be correlated by the noncontact, nondestructive, and convenient QMLT method.

Highly efficient and stable organic solar cells with SnO2 electron transport layer enabled by UV-curing acrylate oligomers

The interfaces between the inorganic metal oxide and organic photoactive layer are of outmost importance for efficiency and stability in organic solar cells (OSCs). Tin oxide (SnO2) is one of the promising candidates for the electron transport layer (ETL) in high-performance inverted OSCs. When a solution-processed SnO2 ETL is employed, however, the presence of interfacial defects and suboptimal interfacial contact can lower the power conversion efficiency (PCE) and operational stability of OSCs. Herein, highly efficient and stable inverted OSCs by modification of the SnO2 surface with ultraviolet (UV)-curable acrylate oligomers (SAR and OCS) are demonstrated. The highest PCEs of 16.6% and 17.0% are achieved in PM6:Y6-BO OSCs with the SAR and OCS, respectively, outperforming a device with a bare SnO2 ETL (PCE 13.8%). The remarkable enhancement of PCEs is attributed to the optimized interfacial contact, leading to mitigated surface defects. More strikingly, improved light-soaking and thermal stability strongly correlated with the interfacial defects are demonstrated for OSCs based on SnO2/UV cross-linked resins compared to OSCs utilizing bare SnO2. We believe that UV cross-linking oligomers will play a key role as interfacial modifiers in the future fabrication of large-area and flexible OSCs with high efficiency and stability.

Overcoming the Interfacial Photocatalytic Degradation of Nonfullerene Acceptor-Based Organic Photovoltaics by Introducing a UV-A-Insensitive Titanium Suboxide Layer.

Although recent dramatic advances in power conversion efficiencies (PCEs) have resulted in values over 19%, the poor photostability of organic photovoltaics (OPVs) has been a serious bottleneck to their commercialization. The photocatalytic effect, which is caused by incident ultraviolet-A (UV-A, 320-400 nm) light in the most commonly used zinc oxide (ZnOX) electron transport layer (ETL), significantly deteriorates the photostability of OPVs. In this work, we develop a new and facile method to enhance the photostability of nonfullerene acceptor-based OPVs by introducing UV-A-insensitive titanium suboxide (TiOX) ETL. Through an in-depth analysis of mass information at the interface between the ETL and photoactive layer, we confirm that the UV-A-insensitive TiOX suppresses the photocatalytic effect. The resulting device employing the TiOX ETL shows excellent photostability, obtaining 80% of the initial PCE for up to 200 h under 1 sun illumination, which is 10 times longer than that of the conventional ZnOX system (19 h).

Understanding photochemical degradation mechanisms in photoactive layer materials for organic solar cells.

Over the past decades, the field of organic solar cells (OSCs) has witnessed a significant evolution in materials chemistry, which has resulted in a remarkable enhancement of device performance, achieving efficiencies of over 19%. The photoactive layer materials in OSCs play a crucial role in light absorption, charge generation, transport and stability. To facilitate the scale-up of OSCs, it is imperative to address the photostability of these electron acceptor and donor materials, as their photochemical degradation process remains a challenge during the photo-to-electric conversion. In this review, we present an overview of the development of electron acceptor and donor materials, emphasizing the crucial aspects of their chemical stability behavior that are linked to the photostability of OSCs. Throughout each section, we highlight the photochemical degradation pathways for electron acceptor and donor materials, and their link to device degradation. We also discuss the existing interdisciplinary challenges and obstacles that impede the development of photostable materials. Finally, we offer insights into strategies aimed at enhancing photochemical stability and discuss future directions for developing photostable photo-active layers, facilitating the commercialization of OSCs.

P3HT:ITIC polymer based photovoltaic biointerfaces for neural photostimulation

Aims/Purpose: Optoelectronic neural interfaces have diverse applications in comprehending neural network and treatment of neurodegenerative conditions especially in the field of the vision impairments. We aimed to use the non‐invasive, capacitive photocurrent generation stimulated by near‐infrared light in the biological environment integrating P3HT:ITIC devices to provide neuroprotective and neurodegenerative effects with reducing axonal damage through local repetitive photo‐stimulation.Methods: In this study, we performed neuron stimulation with the help of ITO/ZnO/P3HT:ITIC photoactive polymer implant placed on an indium tin oxide (ITO) glass. To evaluate the biocompatibility of the P3HT:ITIC devices, CTG cell viability and LDH leak assay were performed on primary nervous and visual system cells including Mio‐M1 and primary astrocytes. Cell specific biomarkers were examined by immunofluorescence staining to demonstrate short‐ and long‐term morphological changes and neural network improvements on both the biointerface and ITO control substrates.Results: We fabricated NIR‐responsive photovoltaic P3HT:ITIC biointerface with ZnO nanoparticles (NPs) as electron transport layer and P3HT:ITIC thin films as photoactive layer on ITO glass substrates. After evaluation of their stability, we showed that primary neurons, astrocytes and Müller glia cells on the biointerface have high cell viability, low cytotoxicity and preserved cellular network and morphology after 2 weeks of culture condition.Conclusions: Our study will provide novel solutions to existing problems in electrostimulation devices by exploring capabilities of wirelessly functional, biocompatible organic polymer‐based photoelectric devices with low cost of production. They have a potential in establishing a platform for the development of near infrared light‐controlled electrostimulation treatment, that can improve axonal healing in retina and optic nerve injuries.

Rational ligand design for enhanced carrier mobility in self-powered SWIR photodiodes based on colloidal InSb quantum dots.

Solution-processed colloidal III-V semiconductor quantum dot photodiodes (QPDs) have potential applications in short-wavelength infrared (SWIR) imaging due to their tunable spectral response range, possible multiple-exciton generation, operation at 0-V bias voltage and low-cost fabrication and are also expected to replace lead- and mercury-based counterparts that are hampered by reliance on restricted elements (RoHS). However, the use of III-V CQDs as photoactive layers in SWIR optoelectronic applications is still a challenge because of underdeveloped ligand engineering for improving the in-plane conductivity of the QD assembled films. Here, we report on ligand engineering of InSb CQDs to enhance the optical response performance of self-powered SWIR QPDs. Specifically, by replacing the conventional ligand (i.e., oleylamine) with sulfide, the interparticle distance between the CQDs was shortened from 5.0 ± 0.5 nm to 1.5 ± 0.5 nm, leading to improved carrier mobility for high photoresponse speed to SWIR light. Furthermore, the use of sulfide ligands resulted in a low dark current density (∼nA cm-2) with an improved EQE of 18.5%, suggesting their potential use in toxic-based infrared image sensors.

Molecular engineering and structure-property relationship based on D-A chlorophyll derivative and the application in organic solar cells.

The photoactive layer materials of organic solar cells (OSCs) play a critical role in achieving excellent performance. Chlorophyll derivatives are commonly used due to their environmental friendliness, low cost, and easy accessibility. However, the efficiency of OSCs based on chlorophyll is limited by their photoelectric properties. Here, we focused on the D-A structure of chlorophyll derivative ZnChl-1 and designed four molecules through rational molecular engineering. The photoelectric properties at the microscopic level were systematically studied using density functional theory (DFT). Our findings reveal that T-ZnChl-1 with triphenylamine donor unit has a smaller energy gap and ionization energy, as well as a larger spectral red shift and absorption range. This suggests that intramolecular charge transfer will be enhanced, leading to an improvement in short-circuit current. Furthermore, Y6 is used as the acceptor to construct the heterojunction interfaces. The results indicate that the T-ZnChl-1/Y6 interface exhibits more charge transfer states and higher exciton dissociation rate KCS, which will promote charge separation and lead to excellent photovoltaic performance. This work clarifies the structure-property relationship of chlorophyll derivatives and the photo-response mechanism of intermolecular charge transfer, providing a theoretical basis for developing valuable chlorophyll-based OSCs.