High Light Utilization Efficiency Research Articles

Enhanced visible light-driven photocathodic protection performance of CuBi2O4 modified TiO2 nanotube array S-type nano-heterojunction photoanodes for 316 stainless steel

CuBi2O4 (CBO) nanoparticle (NP)-sensitized TiO2 nanotube (NT) photoanodes have been prepared and optimized for high visible light utilization and photoconversion efficiency. The introduction of CBO significantly improved the charge generation/separation efficiency of the prepared photoanodes. The CBO-sensitized TiO2 NTs obtained with an electrodeposition time of 6 min had the best photocathodic protection (PCP) performance, and the photogeneration potential of CuBi2O4/TiO2 (CBOT) composites coupled to 316 stainless steel (SS) decreased by an additional 460 mV compared to that of TiO2. The CBO NPs were uniformly distributed on the TiO2 NTs to form tight interfacial bonds. Moreover, the one-dimensional TiO2 NTs act as direct electron channels, ensuring the fast collection of carriers generated by the system. The electronic lifetime of the 6CBOT composite is approximately 30 times that of the pure TiO2 material. In addition, the formation of S-type nano-heterojunction inside the CBOT not only promotes charge transfer in the system, but also retains a strong redox capacity compared to that of single TiO2 NTs. This work offers novel ideas in designing photoanode with efficient PCP property.

Efficient photocatalytic CO2 and Cr(VI) reduction on carbon spheres/g-C3N4 composites with enriched nitrogen vacancies

In this study, carbon spheres (CS)/g-C3N4 composite materials were fabricated by a hydrothermal method, and the characterizations have confirmed the successful anchoring of CS onto the surface of g-C3N4, constructing enriched nitrogen vacancies during the synthesis process. The photocatalytic CO2 reduction activity of g-C3N4 is enhanced by all of these advantageous factors. The significant enhancement can be attributed to the tight interfacial interaction between CS and g-C3N4, which endows with the photocatalyst a larger specific surface area, higher light utilization efficiency and stronger capability for photoinduced charges separation. Furthermore, the presence of nitrogen vacancies further accelerates the separation and migration efficiency of photogenerated charges, provides additional active sites to promote the adsorption and activation of CO2 molecules, thereby effectively boosting the photocatalytic activity for CO2 reduction. The CO2 conversion rate on CS/g-C3N4 composite materials is higher than that on the reference g-C3N4. The apparent quantum yield (AQY) is also superior to that of the reference g-C3N4 under three different monochromatic light irradiations. The stability of the catalyst was verified through cycling experiments, indicating promising potential practical industrial application. The CO2 reduction mechanism and transformation pathways were elucidated using in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The photocatalytic reduction rate constant of Cr(VI) by 50CS/CN is 2.9 times higher than that by CN. This study introduces a facile approach for synthesizing g-C3N4-based photocatalytic materials, providing an interesting strategy to boost photocatalytic activity of g-C3N4 for photocatalytic CO2 and Cr(VI) reduction.

P‐117: A Demura Method For OLED Under White Image With Monochrome Camera

A demura method using high resolution monochrome camera is proposed for OLED panels, enabling single data capturing for white images under different graylevels (GLs). Our method minimizes TACT for low GLs due to its high efficiency of light utilization, compared to demura with color camera of Bayer pattern.

Semitransparent organic solar cells with high light utilization efficiency and color rendering index

Semitransparent organic solar cells with high light utilization efficiency and color rendering index

Guidelines for Material Design in Semitransparent Organic Solar Cells

AbstractOrganic solar cells (OSCs) are uniquely suited for semitransparent applications due to their adjustable absorption spectrum. However, most high‐performance semitransparent cells reported to date are based on materials that have shown high power conversion efficiency for opaque devices. A model is therefore presented to assess the optimum efficiency and transparency for a specific donor and acceptor bandgap. The absorption characteristics of both donor and acceptor are modeled with spectral data of typical absorber materials from the literature which are adjusted to achieve the desired bandgap value. The results show three distinct regions of high light utilization efficiency (LUE) if the photopic curve is employed as a weighting function (corresponding to window applications), and a broad maximum for the plant action spectrum as a weighting function (corresponding to greenhouse applications). When comparing these findings to reported experimental values, it is evident that the bandgaps of the materials used for the experimental studies do not correspond to the maxima identified by the simulation model. The analysis of the energy levels of molecules recorded in the literature confirms that all bandgaps and therefore all LUE maxima are chemically feasible so that the performance of semitransparent OSCs can be further improved by designing materials with optimized absorption spectra.

Efficient and stable semitransparent perovskite photovoltaics via a Lewis base incorporation.

Semitransparent perovskite solar cells (ST-PSCs) have great potential in building integrated photovoltaics. However, semitransparent devices suffer from a low electron mobility and an imbalanced charge-carrier transport, leading to an unsatisfactory power conversion efficiency (PCE) and limited stability. Herein, we report a high-performance ST-PSC via the incorporation of a special Lewis base. A better perovskite with an improved crystallinity and less defects was achieved, and a matched energy level alignment between the perovskite and [6,6]-phenyl-C61-butyric acid methyl ester was also induced, thereby leading to a high electron mobility and an exceptional balance of hole and electron mobility approaching 1 : 1. The prepared ST-PSC exhibited a PCE of 20.22% at average visible transmittance (AVT) of 4.93%, 18.32% at AVT of 14.38%, and 15.00% at AVT of 25.65%. These PCEs are the highest values among those ST-PSCs based on top metallic electrodes at a close AVT. The ST-PSCs maintained 92% of the initial PCE in storage for 1000 h, and they held 84% of the initial PCE under the continuous maximum power point tracking measurement for 530 hours. The work paves the way to realize ST-PSCs with a high PCE, high light utilization efficiency and substantially enhanced stability.

Efficient Semitransparent Organic Solar Cells with CRI over 90% Enabled by an Ultralow‐Bandgap A‐DA'D‐A Small Molecule Acceptor

AbstractSemitransparent organic solar cells (ST‐OSCs) can function as power‐generating windows due to their ability to allow visible light go‐through for human eyesight while absorbing low‐energy photons in the near‐infrared region for photocurrent generation. In this regard, effective ST‐OSCs with high light utilization efficiency (LUE) and color rendering index (CRI) can be developed via a synergistic material and device engineering strategy. Herein, an A‐DA'D‐A acceptor BZO‐4Cl is synthesized with an ultralow optical bandgap of 1.26 eV and bathochromically shifted absorption of roughly 60 nm with respect to Y6. Initially, the opaque devices using PTB7‐Th as the donor show a high power conversion efficiency (PCE) of 14.12% , which can be listed as one of the highest efficiencies for the PTB7‐Th‐based OSCs so far. Then, through these efforts of optimizations in the bulk‐heterojunction(BHJ) composition, top electrodes and anti‐reflection layer, the cutting‐edge ST‐OSC demonstrates a high LUE of 4.02%, and a CRI of 90.67%, making it one of the best‐performing ST‐OSCs with both high LUE and CRI values. These results indicate that the ST‐OSCs presented in this study have significant potential for use in applications that possess transparent visible light and energy‐generation functions.

Photopically Transparent Organic Solar Cells with Tungsten Oxide-Based Multilayer Electrodes.

The tailoring of the average photopic transmittance (APT) of transparent organic solar cells (T-OSCs) has been the greatest challenge in building-integrated photovoltaic applications for future smart solar windows to regulate indoor brightness, maintain a human circadian rhythm, and positively impact human emotions by allowing the observation of the external environment. However, a notorious trade-off exists between the APT and power conversion efficiency (PCE) of T-OSCs, mainly due to the absence of highly conductive and transparent top electrodes, which are a key building block determining the PCE and APT. Herein, we demonstrate a new tungsten oxide (WO3)-based multilayer as a highly conductive and transparent top electrode that provides an excellent APT while maintaining a high PCE in T-OSCs. With the assistance of optical simulation based on a transfer matrix method to calculate the optimum thicknesses of the multilayer electrodes, we achieve the best-performing T-OSC with a PCE of 7.0% and a full device APT of 46.7%, resulting in a high light utilization efficiency of 3.27%, which is superior to that of T-OSCs based on the same photoactive system. Furthermore, superior thermal stability at 85 °C in an N2 atmosphere is observed in WO3-based T-OSCs, maintaining 98% of the initial PCE after about 231 h. Our findings provide new insights into the development of T-OSCs with high efficiency and transparency.

Eliminating the Imbalanced Mobility Bottlenecks via Reshaping Internal Potential Distribution in Organic Photovoltaics.

The imbalanced carrier mobility remains a bottleneck for performance breakthrough in even those organic solar cells (OSCs) with recorded power conversion efficiencies (PCEs). Herein, a counter electrode doping strategy is proposed to reshape the internal potential distribution, which targets to extract the low mobility carriers at far end. Device simulations reveal that the key of this strategy is to partially dope the active layer with a certain depth, therefore it strengthens the electric field for low mobility carriers near counter electrode region while avoids zeroing the electric field near collection electrode region. Taking advantage of these, PCE enhancements are obtained from 15.4% to 16.2% and from 16.9% to 18.0%, respectively, via cathode p-doping and anode n-doping. Extending its application from opaque to semitransparent devices, the PCE of dilute cell rises from 10.5% to 12.1%, with a high light utilization efficiency (LUE) of 3.5%. The findings provide practical solutions to the core device physical problem in OSCs.

A flexible and easily recyclable polyacrylonitrile/Cd0.8Zn0.2S/SnO2 nanofibrous mat for visible-light driven photodegradation of RhB

Constructing photocatalyst with high visible light utilization efficiency and easy recyclability is still challenging in view of practical applications. Herein, we constructed a novel Cd0.8Zn0.2S/SnO2 heterojunction on flexible PAN nanofiber substrates via a simple solvothermal route as a flexible and easily recycled photocatalyst. This newly developed PAN/Cd0.8Zn0.2S/SnO2 nanofibrous mat had excellent photocatalytic activity towards Rhodamine B (RhB) under visible light driving, and RhB could be degraded 98 % after 120 min. The efficient photocarrier separation endowed by Cd0.8Zn0.2S/SnO2 heterojunction plays a significant role in improving photocatalytic property. Meanwhile, the obtained PAN/Cd0.8Zn0.2S/SnO2 nanofibrous mat had good structural stability and cycling performance. More importantly, relative to the traditional suspended nanoparticles, the film-like PAN/Cd0.8Zn0.2S/SnO2 exhibit outstanding flexibility and self-supporting characters, allowing them to be effortlessly separated and removed from service environment. This work provides an excellent strategy for designing flexible and recyclable nanofiber based photocatalysts with high photocatalytic activity, which is expected to have broad application prospects in the field of water treatment.

Preview the Products on Display at Display Week 2023

Preview the Products on Display at Display Week 2023

Metasurface-based polarization color routers

Polarization, an attribute of light, carries a lot of vital information independent of intensity and color content. Polarization imaging is very useful in applications including diffuse/specular component separation, material classification and reflectance estimation. Color routers applied in color imaging provide an efficient way to sort and guide different color lights to the corresponding output ports. Here, we report the design and experimental realization of a compact metasurface-based polarization color router. This color router shows a micron Bayer pattern (RGGB distribution) under the illumination of white light with any polarization. In addition, the green light intensity at the corresponding pixel changes regularly depending on the polarization light, illustrating the polarization color router can act as a polarizer at the same time. The measured light utilization efficiency of the polarization color router reaches a value of 88%. A correlation coefficient of 0.98, which is defined as the fitting effect between the measured and theoretical illuminating light polarization angles, was achieved. This device possesses the advantages of a lightweight, high light utilization efficiency and polarization-integrated detection functions, which could provide a new way for its applications in integrated CMOS image sensors.

Cu-doped SnS2 nanosheets with superior visible-light photocatalytic CO2 reduction performance.

Photocatalytic CO2 reduction utilizing solar energy is a clean, environment-friendly strategy converting CO2 into hydrocarbon fuels to solve the energy crisis and climate issues. Herein, we report the synthesis of Cu-doped SnS2 nanosheets via a simple hydrothermal method. The prepared Cu-doped SnS2 composite displays superior photocatalytic CO2 reduction activity. The optimized CH3OH yield of the composite is two times higher than that of pure SnS2. The enhanced photocatalytic performance is attributed to effective charge separation resulting from the thinner nanosheets and delocalization of electrons from SnS2 to Cu, high visible light utilization efficiency, enlarged SBET, negative shift of the flat-band potential and reduced charge transfer resistance with the introduction of Cu atoms. This work suggests the potential application of Cu-doped SnS2 in photocatalytic CO2 reduction.

The suppressing of excitonic effects in Cu-chalcogenides for solar cell applications

Excitonic effect can usually significantly enhance the optical absorption coefficient in wide-gap insulators. Cu-chalcogenides are widely used as thin-film solar cell absorbers due to their high light utilization efficiency. Theoretical investigations on the excitonic absorption in Cu-chalcogenides are rare because of the complicated two-particle nature of an exciton. Here, we theoretically evaluate the continuum-excitonic effect in CuGaS2 and CuInS2 by solving the Bethe-Salpeter equation. Despite the large bandgap of 2.4 eV for CuGaS2, the excitonic effect induces moderate absorption enhancement when compared with the single-particle scenario. Moreover, the experimental results are better reproduced using the latter approach, indicating that the intrinsic excitonic effect is nearly suppressed in the practical experiments. The moderate intrinsic excitonic effect and its further suppressing in the experiments are explained by strong electronic screening effects in these materials. Justification of the simple single-particle approach would be convenient for future theoretical studies, which otherwise require more complex methods with more expensive computational efforts.

Semi-transparent fullerene-based tandem solar cells with excellent light utilization efficiency enabled by careful selection of sub-cells

Semi-transparent (ST) tandem organic solar cells (OSCs) are typically exhibiting a trade-off between efficiency and average visible transmittance (AVT), which can be minimized by the appropriate selection of transparent contacts and absorbing materials in the sub-cells. Herein, we demonstrate efficient and highly transparent hetero-tandem OSCs constructed by stacking PBDT[2F]T:PC 71 BM and PCE10:PC 61 BM active layers as front-cell and back-cell, respectively. Optical and electrical simulations show that the PBDT[2F]T and PCE10-based sub-cells possess potential as ST and reflective tandem OSCs. With the aid of the simulations, we could fabricate reflective tandem OSCs with an efficiency of up to 8.3%. Furthermore, a ST tandem OSC, employing conductive silver nanowire top contact, achieved an AVT of 49.2%, efficiency of 5.3%, and high light utilization efficiency (LUE) of 2.61% under 1 sun, AM1.5G spectral illumination. This study demonstrates the importance of the sub-cells choices for developing ST tandem solar cells with a good balance of AVT and PCE, paving the way for solar windows of high performance. • Optical and electrical simulations performed to aid reflective and semi-transparent tandem OSCs fabrication. • Fabrication of tandem based on PBDT[2F]T:PC 71 BM and PCE10:PC 61 BM blends with PCE higher than their single-cells (8.2%). • Semi-transparent tandem device with a very high AVT of nearly 50%, in agreement with optical simulation. • The semi-transparent tandem based on PBDT[2F]T:PC 71 BM and PCE10:PC 61 BM blends achieved high PCE of 5.3% and LUE of 2.61%.

Balancing the Selective Absorption and Photon-to-Electron Conversion for Semitransparent Organic Photovoltaics with 5.0% Light-Utilization Efficiency.

Efficiently converting invisible light while allowing full visible light transmission is key to achieving high-performance semitransparent organic photovoltaics (ST-OPVs). Here, a detailed balance strategy is explored to optimize the ST-OPV via taking both absorption and carrier dynamics into consideration. Based on this principle, comprehensive optimizations are carried out, including a ternary strategy, donor:acceptor blend ratio, thickness, antireflection, etc., to compromise the invisible energy conversion and visible transmission for high-performance ST-OPVs. As a result, the opaque OPV device exhibits a champion power conversion efficiency of 19.35% (certificated 19.07%), and most strikingly, the best ST-OPV shows a remarkably high light-utilization efficiency of 5.0%, where the efficiency and the average visible transmission are 12.95% and 38.67%, respectively. An efficiency of 12.09% is achieved on the upscaled device with an area of 1.05 cm2 , demonstrating its promise for large-area fabrication. These results are among the best values for ST-OPVs. Besides, it is demonstrated that the ST-OPV exhibits good infrared light-reflection capability for thermal control. This work provides a rational design of balancing the absorbing selectivity and photon-to-electron conversion for high-performance ST-OPVs, and may pave the way toward the practical application of solar windows.

Analysis of Stray Light and Enhancement of SNR in DMD-Based Spectrometers.

Due to advantages such as the high efficiency of light utilization, small volume, and vibration resistance, digital micro-mirror device (DMD)-based spectrometers are widely used in ocean investigations, mountain surveys, and other field science research. In order to eliminate the stray light caused by DMDs, the stray light in DMD-based spectrometers was first measured and analyzed. Then, the stray light was classified into wavelength-related components and wavelength-unrelated components. Moreover, the noise caused by the stray light was analyzed from the perspective of encoding equation, and the de-noising decoding equation was deduced. The results showed that the accuracy range of absorbance was enhanced from [0, 1.9] to [0, 3.1] in single-stripe mode and the accuracy range of absorbance was enhanced from [0, 3.8] to [0, 6.3] in Hadamard transform (HT) multiple-stripe mode. A conclusion can be drawn that the de-noising strategy is feasible and effective for enhancing the SNR in DMD-based spectrometers.

Biomimetic Janus photothermal membrane for efficient interfacial solar evaporation and simultaneous water decontamination

Solar-driven water evaporation has been regarded as a promising technology to generate clean water due to the abundance and environmental friendliness of solar energy resources. However, the limited clean water production and limitation in tailored solar-driven system (SDS) have impeded its practical application. Herein, inspired by Lemna minor, a biomimetic, hierarchically structured, photothermal membrane (b-HPM) comprising Ti3C2Tx MXene and oxidized carbon nanotubes cross-linkage is designed. The hydrophilic bottom layer of b-HPM with macropores helps promote water transportation whilst the hydrophobic mesoporous upper layer accelerates solar/contaminant absorption and inhibits heat loss. Such-acquired Janus membrane not only improves the water transfer rate to reach 1.66 kg m−2h−1 but also harvests excellent evaporation efficiency of 99.73% deriving from the direct solar light energy (92.58%) and ambient environment (7.15%) under one-sun illumination. Impressively, PPCP removal of > 99% in raw wastewater, and no pollutants were found in the distilled water. More encouragingly, b-HPM enables a high evaporation rate and contaminant removal efficiency in real waterbody with long-term utilization based upon experimental and theoretical calculation results. Our designed SDS synergizes the merits of facile preparation, high light utilization efficiency, high-rate clean water generation, stability and robust performance, holding great promise in solving freshwater shortage and remedying water pollution under natural sunlight.

Theory-Guided Material Design Enabling High-Performance Multifunctional Semitransparent Organic Photovoltaics without Optical Modulations.

Semitransparent organic photovoltaics (ST-OPVs) have drawn great attention for promising applications in building-integrated photovoltaics, providing additional power generation for daily use. A previously proposed strategy, "complementary NIR absorption," is widely applied for high-performance ST-OPVs. However, rational material design toward high performance has not been achieved. In this work, an external quantum efficiency (EQE) model describing this strategy is developed to explore the full potential of material design on ST-OPV performance. Guided by the model, a novel nonfullerene acceptor (NFA), ATT-9, is designed and synthesized, which possesses optimal bandgap for ST-OPVs, achieving a record short-circuit current density of 30mA cm-2 and a power conversion efficiency of 13.40%, the highest value among devices based on NFAs with bandgaps lower than 1.2eV. It is notworthy that, at such a low bandgap, the energy loss of the device is only 0.58eV, which is attributed to the low energetic disorder confirmed by an ultralow Urbach energy of 21.6 meV. Benefiting from the optimal bandgap and low energy loss, the ATT-9-based ST-OPV achieves a high light utilization efficiency of 3.33% without optical modulations, and meanwhile shows excellent thermal insulation, exceeding the commercial 3M heat-insulating window film, demonstrating the outstanding application prospects of multifunctional ST-OPVs.

Tubular photobioreactors illuminated with LEDs to boost microalgal biomass production

This work proposes distinct configurations for tubular photobioreactors (PBRs) illuminated with specific and adequate light wavelength provided by LEDs. The PBRs are characterized by an involute/flat reflective surface around/below a cylindrical borosilicate glass tube that is illuminated by a LEDs panel located above. Reflectors can enlarge the absorber tube's illuminated area, enabling a uniform (spatial and temporal) light distribution across the culture vessel. Additionally, high-energy-efficient LEDs can minimize heat generation and energetic-related costs. Coupling these two factors can result in higher light utilization efficiency and photosynthetic activity. Depending on the reflector design, almost all the light arriving at the collector aperture can be collected and available for microalgal cultivation. Chlorella vulgaris (C. vulgaris) growth was evaluated as a function of the reflector geometry (flat (F), simple double parabola (SP) and traditional double parabola (DP)) and material (anodized aluminum with (MS) and without (R85) protective coating and stainless steel (SS)). C. vulgaris growth as a function of time was found to be in good agreement with the actinometric results, where the parabolic reflectors (SP and DP) made of higher specular reflectance materials (R85 and MS) were the most efficient systems. Conversely, energy-based specific growth rates slightly increased as the photon flux decreased, signaling an energetic efficiency loss due to the low transmissibility of microalgal suspensions. Additional tests using two absorber tubes (spaced between 12.5 and 75.0 mm) over the R85-F reflector were also carried out, showing that the distance of 50.0 mm led to the best compromise between the specific growth rates and biomass productivities per square meter of solar collector. Under these conditions, higher efficiency on the photonic energy usage was attained compared to the single-tube test.