Improvement Of Emission Efficiency Research Articles

Mitigating the disparities in carbon emission efficiency enhancement in China's coal resource-based cities

Enhancing carbon emission efficiency in coal resource-based cities (CRBCs) is pivotal for energy conservation and carbon reduction, but the combined pressures of technical efficiency and technological innovation may drive a sharp disparity in the sustainability of carbon emission efficiency enhancement across such cities. Here, we develop a “Static-Dynamic-Synergistic” progressive assessment framework, to systematically assess the carbon emission efficiency of 51 CRBCs in China from 2000 to 2020. We found that the carbon emission efficiency of CRBCs exhibited a fluctuating upward trajectory, with the average efficiency rising from 0.40 to 0.64. The enhancement of carbon emission efficiency in CRBCs has shifted from relying solely on efficiency change (EC) to incorporating both EC and technology change (TC). TC, EC, and the Carbon Emission Efficiency Improvement Synergy Index (CEEISI) exert a substantial positive influence on the increment of carbon emission efficiency. While the CEEISI of maturity CRBCs has increased by 2.22 % over the past 15 years, varying declines are observed for other types of CRBCs. CRBCs should formulate adaptive policies based on the stage of city development, fostering socio-economic-ecological transformation, synergistically improve technical efficiency and technological innovation, thereby achieving sustainable enhancement in carbon emission efficiency.

Carbon productivity growth in China's thermal power industry: Empirical evidence using a bootstrapped Malmquist-Luenberger productivity index approach with fixed-sum undesirable outputs

The total amount of carbon emissions is limited by a fixed-sum constraint in the context of China's dual carbon target, a factor ignored in previous studies on carbon productivity. To address this gap, this study proposes a bootstrapped Malmquist-Luenberger productivity index approach with fixed-sum undesirable outputs. The proposed method not only considers the fixed-sum feature of undesirable outputs; it also reduces the calculation error caused by small samples and improves the accuracy of the measurement. We then apply the proposed approach to measure the carbon productivity growth of the thermal power industry in 30 provincial regions in China from 2011 to 2020 and analyze the driving forces of carbon productivity growth. The empirical results show that during the study period, China's overall carbon productivity increased with an annual average growth rate of 0.61 % due to CO2 emission efficiency improvement and technological progress. Additionally, 18 provincial thermal power industries had average carbon productivity growth rates between 0.06 % and 4.86 %, while the remaining 12 provinces showed carbon productivity declines at rates ranging from 0.03 % to 2.90 %. The driving forces of such growth differ among the 30 provinces. Policy suggestions are given for improving the carbon productivity of China's thermal power industry.

Modeling and evaluating the impact of variable bus lane on isolated signal intersection performance

Dedicated Bus Lane (DBL) is a typical strategy to ensure priority for public transportation. However, when the frequency of bus departures is low, the DBL often remains vacant, reducing the efficiency of traffic utilization. Variable bus lane (VBL) strategy allows for the provision of service to social vehicles in specific scenarios, aiming to alleviate traffic congestion and improve emission efficiency at intersections. To analyze the impact of this strategy on dynamic queuing behavior and traffic efficiency at an isolated intersection, this paper proposes a multidimensional stochastic queuing model. The model incorporates various factors such as traffic demand, signal timing, bus arrival time, and the length of the variable area at intersections. By examining the steady-state distribution of queue length and calculating performance indicators, the effectiveness of VBL in improving intersection performance is evaluated. Numerical simulations have demonstrated that the proposed model accurately describes the vehicle queuing process at intersections under different conditions. Theoretical analysis confirms that the implementation of VBL strategy can effectively improve traffic efficiency at intersections and minimize the queue length of vehicles.

Unlocking the carbon emission efficiency improvement path of technological innovation: a perspective on industrial restructuring and R&D element flows.

Technological innovation is regarded as an important means to improve carbon efficiency. However, there is no consensus on this view. Meanwhile, few studies have considered how technological innovation affects carbon efficiency. To this end, this study investigates the influencing mechanism and effects of technological innovation on carbon emission efficiency from the perspectives of industrial restructuring and R&D element flow. It establishes the influencing and mechanism model and then deeply studies the impact and paths of technological innovation on carbon emission efficiency, using panel data from 30 provinces in 1999-2020. Results show that (1) technological innovation improves carbon emission efficiency. (2) Regional differences in the impact effects of technological innovation are evident, with a greater contribution to carbon emission efficiency in eastern region. (3) Innovation improves carbon efficiency through two paths: advanced industrial structure and industrial structure rationalization. (4) The moderating effect demonstrates that the technological innovation's influence is gradually enhanced with the interregional mobility of R&D personnel and capital. Hence, decision-makers should correctly guide the orderly flow of R&D factors and further improve the carbon emission reduction effect by increasing innovation support and helping optimize the industrial structure.

Nanostructured Channel for Improving Emission Efficiency of Hybrid Light-Emitting Field-Effect Transistors.

We report on the mechanism of enhancing the luminance and external quantum efficiency (EQE) by developing nanostructured channels in hybrid (organic/inorganic) light-emitting transistors (HLETs) that combine a solution-processed oxide and a polymer heterostructure. The heterostructure comprised two parts: (i) the zinc tin oxide/zinc oxide (ZTO/ZnO), with and without ZnO nanowires (NWs) grown on the top of the ZTO/ZnO stack, as the charge transport layer and (ii) a polymer Super Yellow (SY, also known as PDY-132) layer as the light-emitting layer. Device characterization shows that using NWs significantly improves luminance and EQE (≈1.1% @ 5000 cd m-2) compared to previously reported similar HLET devices that show EQE < 1%. The size and shape of the NWs were controlled through solution concentration and growth time, which also render NWs to have higher crystallinity. Notably, the size of the NWs was found to provide higher escape efficiency for emitted photons while offering lower contact resistance for charge injection, which resulted in the improved optical performance of HLETs. These results represent a significant step forward in enabling efficient and all-solution-processed HLET technology for lighting and display applications.

Impact of labor and energy allocation imbalance on carbon emission efficiency in China's industrial sectors

Greenhouse gas emission is the focus of global climate change concerns. The change in industrial structure can impact carbon emission efficiency (CEE) by affecting labor and energy input. However, there is an obvious imbalance of labor and energy allocation within China's industrial sectors. Here, we use the super-slacks-based model data envelopment analysis (Super-SBM-DEA) to calculate the CEE of 32 industrial sectors and adopt the Tobit model to analyze the impact of industrial allocation imbalance on CEE. The results show that the overall industry and manufacturing CEE is still at a low level, with an average CEE of 0.53. The industrial sectors with higher CEE are these sectors with advanced innovative technology and low energy consumption. The results of the Tobit model show that the imbalance of labor and energy allocation is the key factor limiting carbon emission efficiency improvement. Furthermore, the imbalance of labor allocation hurts the CEE of labor-intensive sectors. The coefficient of labor allocation imbalance (distL) is −2.483, and the inflow of labor can improve the CEE of non-labor-intensive sectors. The CEE of energy-intensive sectors is sensitive to the imbalance of energy allocation, the marginal impact of energy allocation imbalance (distE) is −2.296. Improving energy efficiency is a key task to reduce carbon emissions in sectors relying on energy input. But for non-energy-intensive sectors, optimizing energy allocation has a limited effect on reducing carbon emissions. This research can provide insights for emerging economies to coordinate carbon reduction and industrial transformation.

Does green finance have spatial spillover effects on carbon efficiency in China?

To meet the carbon peaking target, it is critical to understand the spatial impact of green finance. The entropy weight approach is used to create a green finance index. The SBM-GML model was used to calculate carbon efficiency. With SDM model, we analyze how green finance affects carbon efficiency.Transmission mechanism was investigated using threshold and mediation models. In terms of carbon emission efficiency, green finance has a spatial spillover effect, and green finance development can effectively enhance carbon emission efficiency improvement. The effect of green finance on carbon emission efficiency can be enhanced when PGDP and ER exceed a certain level. With a 7.6% effect size, ER played a partial mediation role.

Carbon emission efficiency evaluation of wastewater treatment plants: evidence from China.

A scientific evaluation of the carbon emission efficiency is crucial for ensuring the sustainable development of wastewater treatment plants (WWTPs). In this paper, we applied a non-radial data envelopment analysis (DEA) model to calculate the carbon emission efficiency of 225 WWTPs located in China.The results showed that the average carbon emission efficiency of China's WWTPs was 0.59, indicating that the efficiencies of most samples still require improvement. The carbon emission efficiency of WWTPs from 2015 to 2017 decreased because of the decrease in technology efficiency. Among the influencing factors, different treating scales had positive impact on carbon emission efficiency improvement. WWTPs with anaerobic oxic process and the first-class A standard were likely to have higher carbon emission efficiency in the 225 WWTPs. By incorporating direct and indirect carbon emissions into WWTP efficiency evaluation, this study helped decision-makers and related water authorities to better understand the contribution of WWTPs to the aquatic and atmospheric environments.

Does carbon emission trading scheme really improve the CO2 emission efficiency? Evidence from China's iron and steel industry

The carbon trading market is an effective way to mitigate the threat of climate warming. In the context of carbon neutrality, what is the carbon emission trading scheme's carbon reduction effect? This paper answers the question by examining the carbon efficiency of China's iron and steel industry. This study first constructs CO2 emission efficiency by employing the data envelopment approach. It then uses the synthetic control method to identify the impact of the carbon emission trading scheme on the CO2 efficiency of the iron and steel industry. The results show that CO2 emission efficiency in pilot provinces increased at a 5% significance level compared with the counterfactual scenario. The carbon trading market plays a vital role in industrial CO2 emission efficiency improvement in Guangdong, Shanghai, Tianjin, Hubei, and Chongqing. From a dynamic perspective, the policy effect of enhancing CO2 efficiency becomes more prominent over time. Moreover, the effectiveness degree of the carbon emission trading scheme varies across pilot provinces, caused of regional policy differences. Based on the findings, we put forward targeted suggestions for improving the newly-established national carbon trading market.

Deterioration or improvement? Intermediate product import and enterprises' environmental performance

As an important link in Global Value Chain, intermediate product import is a key method to connect domestic market and foreign market. It can improve country's competitiveness and reduce country's total emissions through import substitution effect. However, the essence of this process is just the transfer of pollution from one country to another. Does importing intermediate products really reduce country's emission intensity and improve its emission efficiency? The above question is significant in reality, but it is still pending at present. In view of this, our research constructs the micro trade model and uses data of Chinese enterprises to investigate causal impact of intermediate product import on emission intensity. We can learn that importing intermediates significantly reduces enterprises' emission intensity. Further analyses shows that rise in enterprises' abatement investment and increase in productivity after importing lead to reduction in emission intensity. This study examines the positive role of intermediate product import in improving emission efficiency from perspective of product trade, revealing importance of intermediate product import in country's economic development and pollution reduction.

Does green financial infrastructure promote the improvement and convergence of regional carbon emission efficiency? Based on provincial data of China

The level of green financial infrastructure is measured using a symbiometric model with the Chinese provincial panel data from 2008 to 2020, and also the carbon emission efficiency is measured using the super-efficient SBM-DEA model with the carbon emission data at the provincial level. This paper tests the carbon emission efficiency improvement and convergence effects of green financial infrastructure using fixed-effects models, non-dynamic panel threshold models and spatial econometric models, while considering the role of environmental regulation in the process. It is found that green financial infrastructure significantly contributes to the improvement of carbon emission efficiency and accelerates the convergence rate of carbon emission efficiency between regions; the carbon emission efficiency improvement and convergence effects of green financial infrastructure are influenced by the intensity of environmental regulation, and we point out that either too strong or too weak environmental regulation will weaken the effectiveness of green financial infrastructure, which means there is a significant threshold effect; the spatial durbin model shows that the effect of green financial infrastructure on carbon emission efficiency has a spatial spillover effect of “neighbors as partners”, that is, while green financial infrastructure promotes the improvement of carbon emission efficiency in the region, it also helps to promote the improvement of carbon emission efficiency in the neighboring regions. Therefore, China should accelerate the improvement of the green financial infrastructure system, improve the carbon emission rights market trading system, enhance the effectiveness of environmental regulation, and strengthen regional economic cooperation, so as to empower the development of low-carbon and green economic transformation.

How Does the Digital Economy Affect Carbon Emission Efficiency? Evidence from Energy Consumption and Industrial Value Chain

China is confronted with the dual constraints of economic transformation and carbon emission reduction. As the digital economy is a key force in promoting economic transformation and optimizing industrial structure, it is crucial to analyze the digital economy’s impact on carbon emission reduction from the perspective of energy consumption and industrial value chain implications. We selected data from 251 prefecture-level cities and above in China from 2011 to 2019 as research samples, measured the development level of the digital economy using the entropy value method, and constructed relevant regression models based on two-way fixed effects, intermediary analysis, and moderation analysis. The research reveals that: (1) The digital economy has a significant contribution to carbon emission efficiency, and there are significant regional heterogeneity and city size differences; (2) The digital economy can improve carbon emission efficiency by reducing energy consumption. (3) From a value chain perspective, industrial structure rationalization weakens the carbon emission efficiency improvement effect of the digital economy to a certain extent, whereas industrial structure upgrading obviously enhances the carbon efficiency improvement effect of the digital economy. The above findings enrich the research in the field of digital economy and environmental governance, contribute to a more comprehensive understanding of the mechanisms by which the digital economy affects the carbon emission efficiency, as well as provide policy implications for enhancing the use of the digital economy in the regional energy consumption and industrial value chain.

Novel benzonitrile-based AIE host with high triplet energy for highly efficient solution-processed blue TADF OLEDs

Developing high-performance host materials for blue thermally activated delayed fluorescence organic light-emitting diodes (TADF-OLEDs) is an effective way to improve emission efficiency through overcoming intermolecular interactions. In this work, three novel AIE-active materials with twisted donor-acceptor structures (3phCN-Cz, 3phCN-ICz and 3phCN-tCzICz) are designed and synthesized by modifying the donor unit. Encouragingly, all the molecules exhibited high triplet energies (>2.80 eV) to prevent exciton returning and aggregation‐induced emission (AIE) property for suppressing exciton quenching. Furthermore, systematic studies demonstrated that 3phCN-ICz and 3phCN-tCzICz with larger steric resistance units can not only possess good thermal and electrochemical stability but also exhibit excellent inhibition ability of intermolecular interactions, which are suitable for constructing high-efficiency solution-processed blue TADF devices. Ultimately, the 4TCzBN was employed as the blue TADF emitter, and the solution-processed OLEDs based on 3phCN-ICz achieved the maximum external quantum efficiency (EQEmax), the maximum current efficiency (CEmax), and the lowest turn-on voltage of 22.04%, 41.88 cd A−1, and 3.5 V, respectively. This work demonstrates the potential application of AIE materials with high triplet energy for solution-processed blue TADF OLEDs.

Is high natural resource dependence doomed to low carbon emission efficiency? Evidence from 283 cities in China

With the increasing concerns of global economic recovery and climate change, the improvement of carbon emission efficiency has become extremely significant to get rid of economic and environmental dilemmas. Although natural resource development is usually carbon-intensive, little attention has been paid to the impact of natural resource dependence on the carbon emission efficiency. Based on the resource curse theory and the stylized facts of resource-based regions in China, for the first time, this paper proposes the hypothesis of the carbon emission efficiency curse. The hypothesis suggests that an increase of natural resource dependence can suppress the carbon emission efficiency by crowding out green technological innovation, curbing the carbon productivity of investment, and reducing population density. Furthermore, we verify the hypothesis using the instrumental variable approach and the panel data of 283 cities in China from 2004 to 2017. The results demonstrate the negative effect of natural resource dependence on the carbon emission efficiency. This finding remains robust after replacing the indicators of the key variables, altering the estimation method, and eliminating the disturbances resulting from particular samples and the low-carbon policy. The mechanism analysis indicates that natural resource dependence can crowd out green technological innovation, restrain the carbon productivity of investment, and lower population density to curb the improvement of the carbon emission efficiency. In addition, the heterogeneity analysis shows that although the carbon emission efficiency curse exists significantly in resource-based cities on average, renewable resource-based cities successfully avoid the carbon emission efficiency curse because of the optimization and transformation of economic development mode. Meanwhile, the negative impact of natural resource dependence on the carbon emission efficiency is not significant in the Two Control Zone cities and key cities for air pollution prevention and control, implying that environmental regulations are conducive to avoiding the carbon emission efficiency curse. This paper provides a novel perspective for the carbon emission efficiency improvement and low-carbon transition of China and other developing countries.

Assessing the impact of the carbon market on the improvement of China's energy and carbon emission performance

All countries are actively taking measures to address carbon neutrality. As a policy measure for China to respond to climate change, the carbon market is necessary and significant for assessing its impact on energy and the environment. This study uses data from 30 provinces in China from 2000 to 2017 and employs a difference-in-differences model to estimate the impact of the carbon market on energy and environmental performance. The empirical results show that the carbon market has significantly improved energy and environmental performance, as shown by a 14.14% reduction in energy intensity and an increase in carbon emission efficiency by 4.21%; a series of robustness test results show that the carbon market only has long-term stability characteristics in reducing energy intensity, but is unstable in improving emission efficiency; market reform and technological innovation have played a significant intermediary role in the impact of the carbon market on energy and environmental performance; and the carbon market has significant heterogeneity effects; only Beijing, Chongqing, and Hubei have significant energy intensity reduction effects. Finally, the results revealed that the carbon market is beneficial for improving energy and environmental performance, which provides a universal reference for countries worldwide to implement carbon emission reduction policies.

Realizing Record‐High Electroluminescence Efficiency of 31.5 % for Red Thermally Activated Delayed Fluorescence Molecules

AbstractTailor‐made red thermally activated delayed fluorescence (TADF) molecules comprised of an electron‐withdrawing pyrazino[2,3‐f][1,10]phenanthroline‐2,3‐dicarbonitrile core and various electron‐donating triarylamines are developed. They can form intramolecular hydrogen‐bonding, which is conducive to improving emission efficiency and promoting horizontal orientation and show near infrared (NIR) emissions (692–710 nm) in neat films and red delayed fluorescence (606–630 nm) with high photoluminescence quantum yields (73–90%) in doped films. They prefer horizontal orientation with large horizontal dipole ratios in films, rendering high optical out‐coupling factors (0.39–0.41). Their non‐doped OLEDs exhibit NIR lights (716–748 nm) with maximum external quantum efficiencies (ηext,max) of 1.0–1.9%. And their doped OLEDs radiate red lights (606–648 nm) and achieve record‐beating ηext,max of up to 31.5%. These new red TADF materials should have great potentials in display and lighting devices.

The role of InGaN quantum barriers in improving the performance of GaN-based laser diodes

In this work, different aspects which have influences on device performance of blue laser diodes (LDs) when using InGaN instead of GaN as quantum barrier (QB) layers are investigated theoretically and experimentally. In the modeling calculation, it is found that the threshold current of LDs with InGaN QB layers is reduced obviously, but the slope efficiency is not largely improved due to the increase of leakage current. However, in the experimental results of the fabricated LDs using InGaN QB layers in comparison with those with GaN QB layers, the slope efficiency is really improved greatly, which is 34% higher. The great improvement of emission efficiency is ascribed to the better homogeneity of the active region which can improve the peak mode gain effectively. Such a better homogeneity of QW layers can be mainly attributed to the decreased composition pulling effect and a suppression of the stress between InGaN QB layers and InGaN QW layers.

Spectral and dynamic analysis of CsPbBr3 perovskite nanocrystals with enhanced water stability using sodium passivation

Sodium (Na) passivated CsPbBr3 nanocrystals (NCs) are synthesized using a modified ligand-assisted reprecipitation method at room temperature. With Na element introducing, small blue-shift absorption and photoluminescence (PL) are observed due to the surface passivation of NCs. The Na passivated NCs with the PL quantum yield of 66% have the improvement of water and thermal stability, with the reduction of 20% comparing with initial PL intensity in water/n-hexane after 12 h and a higher exciton binding energy of 150.8 meV. The spectral and dynamic excitonic recombination for Na: CsPbBr3 NCs are detected by time-resolved PL and transient absorption spectroscopy. The dynamics indicate that the coupling between the lowest excited state and exciton trapping state has significantly enhanced exciton recombination efficiency for Na: CsPbBr3 NCs. It can be observed that faster PL lifetime exists for CsPbBr3 NCs than that of Na: CsPbBr3 NCs in water/n-hexane, which indicates surface defects passivated through sodium incorporation. Na: CsPbBr3 NCs dispersing in NaBr aqueous/nonpolar solution remain bright after 60 days. The obtained results demonstrate that the effective strategies via sodium passivation can improve emission efficiency and stability of perovskite NCs, making them superior potential materials in optoelectronic applications.

Long-Range Ordered Hierarchical Structure Assisted by the Side-Oligoether Network in Light-Emitting Conjugated Polymer for an Efficient Deep-Blue Organic Laser

The supramolecular interaction network between light-emitting conjugated polymer (LCP) chains provides an excellent electronic landscape and optical cavity to stabilize the excited state and enhance emission efficiency for the fabrication of an organic laser. Herein, we originally demonstrated an exceptional deep-blue lasing from uniformly packed nanowires in a robust emissive spherulite of deep-blue LCPs with a flexible oligoether. The supramolecular interactions between flexible side-oligoethers enable polymer chains to self-assemble into crystalline nanowires and attach into a long-range ordered hierarchical structure. Intriguingly, this novel LCP spherulite exhibits an ultrastable and crystalline-enhanced emission, which is enhanced by about 42% over the emission efficiency of pristine spin-coated films. This robust deep-blue emission with an excellent spectral stability is mainly attributed to the suppression of physical defect formation and enhancement of exciton diffusion in these uniformly packed nanowires. More importantly, such a long-range ordered hierarchical structure also provided an excellent optical cavity to realize exciton population inversion for low-threshold (4.22 μJ/cm2) deep-blue lasing behavior. The study indicates that improvement of emission efficiency and stability in a deep-blue conjugated polymer can be achieved in a synergistic way for fabricating a hierarchically ordered superstructure, which will accelerate the future development and application of light-emitting optoelectronic devices.

CO2 emission reduction potential in China from combined effects of structural adjustment of economy and efficiency improvement

China has committed to decreasing its emission intensity by 60% to 65% by 2030 compared to 2005 levels and achieving carbon neutrality by 2060. It is of great importance to evaluate the CO2 emission reduction potential to quantify the amount of CO2 emissions that can be less generated and the amount that should be balanced out. Economic structure adjustment and CO2 emission efficiency improvement will contribute to mitigating CO2 emissions, which always happen simultaneously in the real world. However, few studies consider these issues simultaneously, which can lead to inaccurate estimation. A scenario analysis framework is proposed to estimate their combined effects, and an indicator is proposed to measure the technical feasibility of achieving the reduction potential. A set of scenarios are designed based on this framework and we find that: (1) to achieve carbon neutrality, 6161.16 Mt of CO2 emissions of China can be less generated compared to 2017 levels by significantly increasing its tertiary industry share to high-income entities’ level and adopting the most advanced technology to improve emission efficiency; the remaining 2732.40 Mt of CO2 emissions should be removed by carbon offsetting. Regarding emission intensity, 81.39% can be reduced compared with the 2005 level; and (2) Technical feasibility analysis shows Sichuan, Chongqing, and Anhui have the largest technical barriers in achieving the reduction potential. The proposed scenario analysis framework can provide a reference not only for China to achieve the emission mitigation pledges, but for countries with significant technological differences and structure adjustment to formulate mitigation strategies.