Method For Fabrication Of Devices Research Articles

1D Metal Oxide Semiconductor Materials for Chemiresistive Gas Sensors: A Review

AbstractWhile numerous types of gas sensors have been developed for various industries and applications such as the automotive industry, environmental monitoring, and personal safety, nanoscale chemiresistive gas sensors have gained significant research interest due to several advantages such as high sensitivity, low power consumption, and portability. An essential component of these gas sensors is the sensing material where metal oxide semiconductor (MOS) materials are the most prevalent sensing material. Since the adoption of nanoscale synthesis methods for sensing materials development, such as electrospinning and hydrothermal synthesis, many novel 1D MOS‐based nanostructured sensing materials have been demonstrated to enhance gas sensing performance. Overall, nanoengineering approaches and mechanisms for enhancement of gas sensing performance of 1D metal oxide‐based sensing materials are systematically discussed and categorized into several overarching strategies, such as tuning of materials dimension, morphology, and composition. Furthermore, integration of 1D sensing nanomaterials into sensor devices are discussed from the perspective of different chemiresistive sensor architectures and device fabrication methods. Finally, this review also discusses use of 1D MOS materials for emerging and novel electronic nose applications.

Design of Highly Sensitive and Selective H2s Gas Sensor Based on CuO-Cu7S4 Microflowers

Introduction CuxO (copper oxides, x=1, 2) as a p-type oxide semiconductor is widely used in photocatalysis, electrochemistry, solar energy conversion, gas sensors [1], and photoactivated splitting of water due to its non-toxicity, low cost, and facile controllable synthesis. In order to meet the increasing requirements of the above applications, various morphologies of CuxO such as nanocubes [2], nanowires [3], nanorods, nanoflowers, nanoparticles, nano-octahedrons, nanospheres, have been prepared by different methods. In this work, CuO-Cu7S4 microflowers were successfully synthesized through a simple hydrothermal route and used as sensing materials. In the comparative gas sensing test, the sensor fabricated from CuO-Cu7S4 (S/Cu = 27 mol%) microflowers exhibited the highest response to hydrogen sulfide, and the fast response and recovery time. CuO-Cu7S4 microflowers gas sensor showed not only superior hydrogen sulfide selectivity with other gases, but also ppb-level detection limit at 225 °C. The synergistic catalytic effect between CuO and Cu7S4, optimized structural parameters and marked resistive variation due to the formation of nanoscale p-p heterojunctions were regarded as the main reasons for the ultrasensitive and selective hydrogen sulfide detection. Method For device fabrication, a small amount of CuO-Cu7S4 microflowers were dissolved with a few drops of the deionized water in an agate mortar to form slurry and then coated uniformly on the ceramic tube (4 mm in length, 1.2 mm in external diameter and 0.8 mm internal diameter) with a pair of Au electrodes and Pt wires. The coating was calcined at 90 °C for 1 h in air using a muffle furnace. Then, a Ni-Cr alloy coil heater was inserted through the well-coated ceramic tube, which controlled the working temperature. The sensing measurement of the sensors was carried out on a static system. The resistance of sensing material was continuously recorded by digital multimeter and the sensing response (S) was defined as the percentage of relative variation in resistance (ΔR/Ra*100%), where ΔR represents the variation of resistance before and after contacting with target gases, while Ra represents the resistance of gas sensor in initial state. The response/recovery time was defined as the required time for the resistance to reach 90% of total resistance variation relative to the former equilibrium value upon exposure to/removal from target gases. Results and Conclusions In this work, the Cu7S4-CuO composites were synthesized by hydrothermal method, More importantly, the ppb-level detection limit indicated the potential application on the trace hydrogen sulfide detection. Such behaviors could be attributed to the existence of p-p heterojunctions, co-catalytic effect, the large BET surface areas and the synergistic combination between Cu7S4 and CuO.

Direct Optoelectronic Imaging of 2D Semiconductor-3D Metal Buried Interfaces.

The semiconductor-metal junction is one of the most critical factors for high-performance electronic devices. In two-dimensional (2D) semiconductor devices, minimizing the voltage drop at this junction is particularly challenging and important. Despite numerous studies concerning contact resistance in 2D semiconductors, the exact nature of the buried interface under a three-dimensional (3D) metal remains unclear. Herein, we report the direct measurement of electrical and optical responses of 2D semiconductor-metal buried interfaces using a recently developed metal-assisted transfer technique to expose the buried interface, which is then directly investigated using scanning probe techniques. We characterize the spatially varying electronic and optical properties of this buried interface with <20 nm resolution. To be specific, potential, conductance, and photoluminescence at the buried metal/MoS2 interface are correlated as a function of a variety of metal deposition conditions as well as the type of metal contacts. We observe that direct evaporation of Au on MoS2 induces a large strain of ∼5% in the MoS2 which, coupled with charge transfer, leads to degenerate doping of the MoS2 underneath the contact. These factors lead to improvement of contact resistance to record values of 138 kΩ μm, as measured using local conductance probes. This approach was adopted to characterize MoS2-In/Au alloy interfaces, demonstrating contact resistance as low as 63 kΩ μm. Our results highlight that the MoS2/metal interface is sensitive to device fabrication methods and provide a universal strategy to characterize buried contact interfaces involving 2D semiconductors.

Organic Thin-Film Transistors as Gas Sensors: A Review.

Organic thin-film transistors (OTFTs) are miniaturized devices based upon the electronic responses of organic semiconductors. In comparison to their conventional inorganic counterparts, organic semiconductors are cheaper, can undergo reversible doping processes and may have electronic properties chiefly modulated by molecular engineering approaches. More recently, OTFTs have been designed as gas sensor devices, displaying remarkable performance for the detection of important target analytes, such as ammonia, nitrogen dioxide, hydrogen sulfide and volatile organic compounds (VOCs). The present manuscript provides a comprehensive review on the working principle of OTFTs for gas sensing, with concise descriptions of devices’ architectures and parameter extraction based upon a constant charge carrier mobility model. Then, it moves on with methods of device fabrication and physicochemical descriptions of the main organic semiconductors recently applied to gas sensors (i.e., since 2015 but emphasizing even more recent results). Finally, it describes the achievements of OTFTs in the detection of important gas pollutants alongside an outlook toward the future of this exciting technology.

Melt Blown Fiber-Assisted Solvent-Free Device Fabrication at Low-Temperature.

In this paper, we propose a solvent-free device fabrication method using a melt-blown (MB) fiber to minimize potential chemical and thermal damages to transition-metal-dichalcogenides (TMDCs)-based semiconductor channel. The fabrication process is composed of three steps; (1) MB fibers alignment as a shadow mask, (2) metal deposition, and (3) lifting-up MB fibers. The resulting WSe2-based p-type metal-oxide-semiconductor (PMOS) device shows an ON/OFF current ratio of ~2 × 105 (ON current of ~−40 µA) and a remarkable linear hole mobility of ~205 cm2/V·s at a drain voltage of −0.1 V. These results can be a strong evidence supporting that this MB fiber-assisted device fabrication can effectively suppress materials damage by minimizing chemical and thermal exposures. Followed by an MoS2-based n-type MOS (NMOS) device demonstration, a complementary MOS (CMOS) inverter circuit application was successfully implemented, consisted of an MoS2 NMOS and a WSe2 PMOS as a load and a driver transistor, respectively. This MB fiber-based device fabrication can be a promising method for future electronics based on chemically reactive or thermally vulnerable materials.

Completely Additive Manufactured and Reusable Microfluidic Device As Enzymatic Glucose Biofuel Cell

Energy devices using electrochemical reactions are emerging as essential power sources, paving the way towards renewable and sustainable energy harvesting. Among various electrochemical energy devices (ECD), enzymatic biofuel cells (EBFC) are gaining more attention due to the production of green energy using biocatalysts such as enzymes and physiological fluids as fuel. These devices are of prime importance because of their unique features, such as high energy density, long-life, portability, and cost-effectiveness. However, they still have some drawbacks including precise and customized designing of devices at the microscale dimensions. This can be overcome by additive manufacturing techniques such as fused deposition modeling (FDM) driven 3D printing to produce accurate micro-devices using conductive filaments with tailored design. In this work, the development of a completely additively manufactured (AM) microfluidic device for the application of enzymatic biofuel cells has been described. The micro-device was 3D printed with ABS filament, whereas the electrodes using conductive graphene/polylactic acid filament using a desktop 3D printer. The design of the electrodes (Figure 1a) (35 mm × 1.5 mm × 1 mm) and microchannel were carried out using Autodesk Fusion 360 software with the required dimensions. Surface modification of the electrode was accomplished using dimethylformamide (DMF) for an optimized time of 10 mins (Figure 1b) and left to air dry overnight. The anodic (glucose oxidase) and cathodic (laccase) enzymes were immobilized on the bioelectrodes by the EDC-NHS coupling mechanism (Figure 1c and 1d). The substrate (glucose) concentration and DMF treatment time were optimized by various trials using electrochemical techniques. The microfluidic device was designed in a way that the device can be reused by inserting bioelectrodes into the respective compartments. The anolyte and catholyte consisted of mediators for enhancing the electron transfer rate during electrolysis. Co-laminar flow was maintained in the device to make it membraneless. This was done by varying the device design parameters and flow rates of the electrolyte with the help of a peristaltic pump. The sequential steps of integration of the bioelectrodes into the microchannel is shown in Figure 1e. Polarization performance of the fabricated bioelectrodes incorporated in the AM microfluidic EBFC was recorded using Chronoamperometry technique at the room temperature. The device was capable of generating a benchmarked power density of 7.95 µW/cm2 with an open circuit voltage of 312 mV. This method of device fabrication for EBFC will help in development of highly efficient ECD by different conductive electrode materials for increasing the efficacy of the micro-device. Figure 1

Electron beam lithography induced doping in multilayer MoTe2

Molybdenum ditelluride (MoTe2) is an excellent building block for assembling switching devices owing to its appropriate band gap, tunable p- and n-type conduction. Electron beam lithography (EBL) as a powerful method for electronic device fabrication, generally involves thermal process for resist solidification and electron beam writing. Herein, we find that thermal processing in air and electron beam irradiation result in significant p- and n-doping in multilayer MoTe2, respectively. The p- and n-doping levels can be precisely controlled by the annealing temperature (time) and injection Cullen density, respectively. Both p-doping by annealing and n-doping using irradiation are reversible and can realize degenerate-like conduction behavior. The annealing-induced adsorption of molecules as electron acceptors (e.g. O2, H2O) on the surface MoTe2 accounts for the p-doping, whereas irradiation-induced desorption and interface charging are probably responsible for the n-doping. Polymethyl methacrylate (PMMA) coating does not completely hinder but mitigate the p-doping by annealing. In contrast, PMMA coating is invalid in inhibition of the n-doping by irradiation. These findings would promote understanding of the transport properties of intrinsic MoTe2. Besides, the facile, reversible and controllable p- and n-doping methods are helpful for assembling novel electronics with diverse functionality.

Monolithic focus-tunable lens technology enabled by disk-type dielectric-elastomer actuators

We propose a monolithic focus-tunable lens structure based on the dielectric-elastomer actuator (DEA) technology. In our focus-tunable lens, a soft lens and radial in-plane actuator mimicking the ocular focal-tuning mechanism are constructed in a single body of an optimized dielectric-elastomer film. We provide device fabrication methods including elastomer synthesis, structure formation, and packaging process steps. Performance test measurements show 93% focal tunability and 7 ms response time under static and dynamic electrical driving conditions, respectively. These performance characteristics are substantially enhanced from the previous polylithic DEA tunable lens by a factor 1.4 for the focal tunability and a factor 9.4 for the dynamic tuning-speed limit. Therefore, we obtain greatly enhanced focal tuning control in a remarkably simple and compact device structure.

A novel, low cost, and accessible method for rapid fabrication of the modifiable microfluidic devices

As microfluidic chips are evolving to become a significant analysis tool toward POCT devices, it is crucial to make the cost and the time required for the fabrication process of these chips as low as possible. Because of the multidisciplinary nature of these systems and the collaboration of many different laboratories and organizations from vastly various fields with unequal types of equipment, it is essential to develop new techniques and materials to make the integration of disparate systems together more straightforward, accessible, and economical. In this paper, we present ethylene–vinyl acetate (EVA) as a new polymer-based material for the fabrication of different microfluidic chips, which brings new features and tools in fabrication, integration, and functionality of microfluidic systems. We put this material next to PDMS for comparison between various aspects of these materials. We have shown that besides the low-cost ability, ubiquitousness, geometrical modifiability, and ease of fabrication of EVA chips, due the lower hydrophobicity and lower terahertz (THz) absorption of EVA than PDMS, EVA chips, in comparison to PDMS counterparts, can work faster, have less number of channel blocking and can be used in THz biosensing application like metamaterial-based cancer detection. Finally, several devices are made using EVA to demonstrate the functionality and versatility of this material for the fabrication of microfluidic chips.

Bifacial Perovskite Solar Cells via a Rapid Lamination Process

Hybrid perovskite solar cells are considered a promising choice for next-generation thin-film photovoltaic technology. To meet commercialization requirements, more research efforts have now been focused on developing potentially high throughput fabrication methods compatible with perovskite chemistry. Here we show that bifacial perovskite solar cells can be made by a rapid lamination process in ambient air within 60 s. Upon optimization, these devices show an average single-side efficiency above 15% and bifaciality of 0.93. The bifacial feature enables light collection from both sides and can boost the overall performance by 10% or more. These results and further studies can provide unique opportunities to design new device architectures and fabrication methods for highly functional perovskites photovoltaics.

Recent Progress on Cu2BaSn(SxSe1–x)4: From Material to Solar Cell Applications

Thin film solar cells show great potential applications in building‐integrated photovoltaics (BIPV) and portable devices. Among these thin film solar cells, Cu2BaSn(SxSe1–x)4 solar cells derived from Cu2ZnSn(SxSe1–x)4 solar cells have attracted intense research interests recently because of their high theoretical PCE of ap;31%, easy tunability of band gaps (Eg = 1.28–1.79 eV), large optical absorption coefficient (α &gt; 104 cm−1), environment‐friendly composition, low materials, and fabrication cost. Importantly, Cu2BaSn(SxSe1–x)4 solar cells are expected to have low open‐circuit voltage deficit, leading to high open‐circuit voltage and PCEs. In fact, since their initial development in 2016, the maximum PCE of Cu2BaSn(SxSe1–x)4 solar cells has surpassed 5% via adjustment of the fabrication methods and material properties, optimization of the device structures, and so forth. Here, a review of the recent progress of Cu2BaSn(SxSe1–x)4 solar cells is presented, including properties of Cu2BaSn(SxSe1–x)4, material and device fabrication methods, device performances, potential applications, as well as the bulk and interface recombination. In addition, other solar cells which are similar with the Cu2BaSn(SxSe1–x)4 solar cells are also discussed. Finally, according to these discussions, prospect for PCEs improvement is given to accelerate their development.

Perovskite Solar Cells an Efficient, Low Cost, Emerging Photovoltaic Technology

Organometal halides compound shortly named as perovskite represent an emerging active layer materials for photovoltaic technology. In recent years perovskite shows capability of developing high performance photovoltaic devices with higher efficiency at a low cost. This review article discuss the current status of methylammonium metal halide (perovskite) based photovoltaic devices and provide a comprehensive review of ABX3 device structures, fabrication methods,synthetization, film properties, and photovoltaic performance. The flexibility, simplicity and low cast processing of perovskite solar cell fabrication methods allow using various types of device architectures. The article also focuses on the journey of perovskite solar cell. In 2009 first perovskite solar cell was reported and it shows power conversion efficiency (PCE) of around 3–4%.In 2017 the PCE was reported around 22.1%, now a day (in 2019) 28% power conversion efficiency is reported by Oxford PV’s which is tandem solar cell based on perovskite-silicon. In this article the issue related to efficiency enhancement, stability and degradation mechanism are presented.

Pushing the Limits of Spatial Assay Resolution for Paper-Based Microfluidics Using Low-Cost and High-Throughput Pen Plotter Approach.

To transform from reactive to proactive healthcare, there is an increasing need for low-cost and portable assays to continuously perform health measurements. The paper-based analytical devices could be a potential fit for this need. To miniaturize the multiplex paper-based microfluidic analytical devices and minimize reagent use, a fabrication method with high resolution along with low fabrication cost should be developed. Here, we present an approach that uses a desktop pen plotter and a high-resolution technical pen for plotting high-resolution patterns to fabricate miniaturized paper-based microfluidic devices with hundreds of detection zones to conduct different assays. In order to create a functional multiplex paper-based analytical device, the hydrophobic solution is patterned on the cellulose paper and the reagents are deposited in the patterned detection zones using the technical pens. We demonstrated the effect of paper substrate thickness on the resolution of patterns by investigating the resolution of patterns on a chromatography paper with altered effective thickness. As the characteristics of the cellulose paper substrate such as thickness, resolution, and homogeneity of pore structure affect the obtained patterning resolution, we used regenerated cellulose paper to fabricate detection zones with a diameter as small as 0.8 mm. Moreover, in order to fabricate a miniaturized multiplex paper-based device, we optimized packing of the detection zones. We also showed the capability of the presented method for fabrication of 3D paper-based microfluidic devices with hundreds of detection zones for conducting colorimetric assays.

A one-step polymer screen-printing method for fabrication of microfluidic cloth-based analytical devices

We report the first use of a one-step polymer screen-printing method for fabrication of microfluidic cloth-based analytical devices (µCADs). The method involves a simple, low-cost and one-step fabrication process and requires only polystyrene and a patterned screen. Firstly, polystyrene solution is poured through the patterned screen and allowed to penetrate through the cotton fabrics to create a three-dimensional hydrophobic barrier which defined the test zones. Different types of cotton fabric and polystyrene concentrations were first investigated. By adjusting polystyrene concentration, various types of cotton cloth can be successfully fabricated. Under optimal condition, the smallest hydrophilic channel and hydrophobic barrier that the fabrication method can provide were 678 ± 59 µm and 329 ± 27 µm, respectively. High device-to-device repeatability was achieved with a relative standard deviation (%RSD) in the range of 1.10–2.03% (n = 64) obtained from the measured diameter of the circular-shaped fabricated test zones with a designed diameter of 5 and 7 mm. The cloth treatments using hot water, Na2CO3 and NaOH solutions were found to affect the wicking ability of the cloths where the highest wicking rate was found in the Na2CO3 treated-cloth followed by NaOH, hot water treated-cloths and untreated-cloth. To demonstrate the significance of the fabricated µCAD, the analysis of glucose and albumin in control human serum was carried out. The results showed no significant difference at 95% confident intervals of the glucose and albumin levels obtained from the µCAD analysis and the certified values verifying that the polymer-screen printing method can be alternatively used as a method for µCAD fabrication.

A Potential Checkmate to Lead: Bismuth in Organometal Halide Perovskites, Structure, Properties, and Applications.

The remarkable optoelectronic properties and considerable performance of the organo lead‐halide perovskites (PVKs) in various optoelectronic applications grasp tremendous scientific attention. However, the existence of the toxic lead in these compounds is threatening human health and remains a major concern in the way of their commercialization. To address this issue, numerous nontoxic alternatives have been reported. Among these alternatives, bismuth‐based PVKs have emerged as a promising substitute because of similar optoelectronic properties and extended environmental stability. This work communicates briefly about the possible lead‐alternatives and explores bismuth‐based perovskites comprehensively, in terms of their structures, optoelectronic properties, and applications. A brief description of lead‐toxification is provided and the possible Pb‐alternatives from the periodic table are scrutinized. Then, the classification and crystal structures of various Bi‐based perovskites are elaborated on. Detailed optoelectronic properties of Bi‐based perovskites are also described and their optoelectronic applications are abridged. The overall photovoltaic applications along with device characteristics (i.e., V OC, J SC, fill factor, FF, and power conversion efficiency, PCE), fabrication method, device architecture, and operational stability are also summarized. Finally, a conclusion is drawn where a brief outlook highlights the challenges that hamper the future progress of Bi‐based optoelectronic devices and suggestions for future directions are provided.

A Flexible Method for Nanofiber-based 3D Microfluidic Device Fabrication for Water Quality Monitoring.

Water pollution seriously affects human health. Accurate and rapid detection and timely treatment of toxic substances in water are urgently needed. A stacked multilayer electrostatic printing technique was developed for making nanofiber-based microfluidic chips for water-quality testing. Nanofiber membrane matrix structures for microfluidic devices were fabricated by electrospinning. A hydrophobic barrier was then printed through electrostatic wax printing. This process was repeatedly performed to create three-dimensional nanofiber-based microfluidic analysis devices (3D-µNMADs). Flexible printing enabled one-step fabrication without the need for additional alignment or adhesive bonding. Practical applications of 3D-µNMADs include a colorimetric platform to quantitatively detect iron ion concentrations in water. There is also great potential for personalized point-of-care testing. Overall, the devices offer simple fabrication processes, flexible prototyping, potential for mass production, and multi-material integration.

Liquid Phase Exfoliated Indium Selenide Based Highly Sensitive Photodetectors

AbstractLayered semiconductors of the IIIA–VIA group have attracted considerable attention in (opto)electronic applications thanks to their atomically thin structures and their thickness‐dependent optical and electronic properties, which promise ultrafast response and high sensitivity. In particular, 2D indium selenide (InSe) has emerged as a promising candidate for the realization of thin‐film field effect transistors and phototransistors due to its high intrinsic mobility (&gt;102 cm2 V−1 s−1) and the direct optical transitions in an energy range suitable for visible and near‐infrared light detection. A key requirement for the exploitation of large‐scale (opto)electronic applications relies on the development of low‐cost and industrially relevant 2D material production processes, such as liquid phase exfoliation, combined with the availability of high‐throughput device fabrication methods. Here, a β polymorph of indium selenide (β‐InSe) is exfoliated in isopropanol and spray‐coated InSe‐based photodetectors are demonstrated, exhibiting high responsivity to visible light (maximum value of 274 A W−1 under blue excitation 455 nm) and fast response time (15 ms). The devices show a gate‐dependent conduction with an n‐channel transistor behavior. Overall, this study establishes that liquid phase exfoliated β‐InSe is a valid candidate for printed high‐performance photodetectors, which is critical for the development of industrial‐scale 2D material‐based optoelectronic devices.

Advances in Paper-Based Analytical Devices.

Microfluidic paper-based analytical devices (μPADs) are the newest generation of lab-on-a-chip devices and have made significant strides in both our understanding of fundamental behavior and performance characteristics and expansion of their applications. μPADs have become useful analytical techniques for environmental analysis in addition to their more common application as medical point-of-care devices. Although the most common method for device fabrication is wax printing, numerous other techniques exist and have helped address factors ranging from solvent compatibility to improved device function. This review highlights recent reports of fabrication and design, modes of detection, and broad applications of μPADs. Such advances have enabled μPADs to be used in field and laboratory studies to address critical needs in fast, cheaper measurement technologies.

Electrical and optical properties of composite PEDOT:PSS-based thin films with NiO nanoparticles

Due to the combination of low cost materials deposition and device fabrication methods as well as competitive efficiency compared to the other Si solar cell architectures, the hybrid organic-silicon solar cells have attracted attention of the scientific community. It has recently been demonstrated that spin-coated poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (hereafter PEDOT:PSS) on a silicon wafer is a promising material due to its good optical and electrical properties. However, degradation caused by atmospheric exposure and relatively poor passivation properties limits implementation of PEDOT:PSS–silicon devices. Functionalization of PEDOT:PSS by inorganic nanoparticles might provide a possible solution as was shown for TiO2 and SnO2 nanoparticles. In this contribution, we present our results on spin-coated PEDOT:PSS thin-films with NiO nanoparticles. We show that PEDOT:PSS mixed with Triton X-100 and dimethyl sulfoxide (DMSO) or ethylene glycol (EG) form a homogenous film and passivates the Si surface with charge carrier lifetimes of 300–400 µs with good reproducibility. Time-resolved measurements revealed continuous degradation of the passivation properties in air, however saturation of the degradation at approximately 150 µs was observed in N2 atmosphere. The influence of the NiO nanoparticles on the optical properties of PEDOT:PSS is negligible, whereas the surface passivation properties are worsened due probably to the formation of large size agglomerates exceeding thickness of PEDOT:PSS film.

3D-Structured Carbonized Sunflower Heads for Improved Energy Efficiency in Solar Steam Generation.

Solar steam generation is regarded as a perspective technology, due to its potentials in solar light absorption and photothermal conversion for seawater desalination and water purification. Although lots of steam generation systems have been reported to possess high conversion efficiencies recently, researches of simple, cost-effective, and sustainable materials still need to be done. Here, inspired by natural young sunflower heads' property increasing the temperature of dish-shaped flowers by tracking the sun, we used 3D-structured carbonized sunflower heads as an effective solar steam generator. The evaporation rate and efficiency of these materials under 1 sun (1 kW m-2) are 1.51 kg m-2 h-1 and 100.4%, respectively, beyond the theoretical limit of 2D materials. This high solar efficiency surpasses all other biomass-based materials ever reported. It is demonstrated that such a high capability is mainly attributed to the 3D-structured top surface, which could reabsorb the lost energy of diffuse reflection and thermal radiation, as well as provide enlarged water/air interface for steam escape. 3D-structured carbonized sunflower heads provide a new method for the future design and fabrication of high-performance photothermal devices.