Reduce Efficiency Losses Research Articles

Unravel the Distinctive Roles of Liquid and Solid Additives in Blade‐Coated Active Layer for Organic Solar Cell Modules

AbstractAlthough encouraging progress in spin‐coated small‐area organic solar cells (OSCs), reducing efficiency loss caused by differences in film uniformity and morphology when up‐scaled to large‐area modules through meniscus‐guided coating is an important but unsolved issue. In this work, in‐depth research is conducted on the influence of both liquid and solid additives on the film uniformity and morphology of active layer in blade‐coated PM6:L8‐BO binary system. The study reveals that high boiling point liquid additives like 1,8‐diiodooctane (DIO) used in blade‐coating not only delay the volatilization of the solvent but also trigger the Marangoni flow in the same direction as capillary flow, causing excessive aggregation of acceptors, therefore destroying device performance. On the contrary, the solid additive 2‐Iododiphenyl ether (IDPE), which is first reported in this work, can preserve the mechanism for improving device performance while effectively suppressing the excessive aggregation of acceptors during the film‐forming process in blade‐coating from halogen‐free solvent of toluene, resulting in highly homogeneous large‐area active layer films. Consequently, organic solar modules with an impressive efficiency of 15.34% with a total module area of 18.90 cm2 via blade‐coating based on PM6:L8‐BO are achieved. This study not only provides a deep understanding on the effect of liquid and solid additives during blade‐coating from the perspective of fluid mechanisms but also gives a pathway for the development of green solvent printed high‐efficiency OSCs.

Phosphor-in-glass film sintered on sapphire lens for laser welding hermetic packaging of high-power white LEDs

White light-emitting diodes (WLEDs) represent a revolutionary type of energy-saving and environmentally friendly light source, which has been extensively employed in a multitude of lighting and display applications. Nevertheless, traditional organic packaging is unable to fulfill the requirements of highly reliable high-power WLEDs, including hemertic property, heat resistance, and excellent luminous properties. Herein, an all-inorganic hermetic packaging based on laser-localized welding and phosphor-in-glass film sintered on a sapphire lens (PiGF-SL) has been developed for high-power WLEDs. The PiGF-SL with a Kovar frame was welded to a three-dimensional direct-plated ceramic (3D-DPC). The high-strength and crack-free welded joint with a shear strength of 258.83 MPa and packaging cavity with excellent gas tightness (leakage rate 8.6 × 10−10 Pa m3/s) were simultaneously obtained, resulting in the high-power WLED capable of maintaining its excellent optical properties for an extended period in harsh environments. Furthermore, the optical performance of welded WLEDs was optimized by adjusting the PiGF-SL film thickness and red CaAlSiN3:Eu2+ (CASN) phosphor content. The welded WLED emits a cool white light by improving the PiGF thickness to 91 μm and exhibits high color quality with red CASN phosphor content of 8 wt%, which simultaneously presents outstanding color rendering index (CRI) of 91, luminous efficacy (LE) of 44.8 lm/W, and correlated color temperature (CCT) of 4322 K. Following a 200-h aging process, the laser-welded PiGF-SL-based WLED exhibited a slightly reduced efficiency loss and a stable color quality in comparison to reflow-soldered and epoxy-bonded WLEDs. Our work provides valuable guidance and solutions for the highly reliable and board-level packaging of WLEDs.

Method to Study Potential‐Induced Degradation of Perovskite Solar Cells and Modules in an Inert Environment

The efficiency of perovskite solar cells (PSCs) is advancing rapidly, yet their sensitivity to ambient conditions poses challenges. An additional degradation mechanism, potential‐induced degradation (PID), can emerge during field operation, but the understanding of PID within perovskite devices is limited. To exclude environmental stressors, this study is conducted in an inert environment at room temperature. PSCs and mini‐modules are subjected to a 324 h PID stress test at −1000 V, revealing relative efficiency losses of around 29% and 24% for the PSCs and mini‐modules, respectively, exposing subtle degradation differences. These degradation rates are notably lower than reported in the literature, suggesting possible additional degradation pathways arising from suboptimal encapsulation combined with ambient conditions. Subsequently, half of the stressed samples are subject to +1000 V for 523 h and recover to a reduced efficiency loss of 15% and 7.7% for the PSCs and module, respectively. In contrast, storing the stressed samples on the shelf increased the efficiency losses to 32% (PSCs) and 41% (module). Therefore, the post‐PID rates differ significantly between both groups, whereas both effects of voltage recovery and progressed degradation are more pronounced in modules compared to cells. This study contributes to a robust method for PID research.

Delayed Crystallization Kinetics Allowing High-Efficiency All-Polymer Photovoltaics with Superior Upscaled Manufacturing.

Though encouraging performance is achieved in small-area organic photovoltaics (OPVs), reducing efficiency loss when evoluted to large-area modules is an important but unsolved issue. Considering that polymer materials show benefits in film-forming processability and mechanical robustness, a high-efficiency all-polymer OPV module is demonstrated in this work. First, a ternary blend consisting of two polymer donors, PM6 and PBQx-TCl, and one polymer acceptor, PY-IT, is developed, with which triplet state recombination is suppressed for a reduced energy loss, thus allowing a higher voltage; and donor-acceptor miscibility is compromised for enhanced charge transport, thus resulting in improved photocurrent and fill factor; all these contribute to a champion efficiency of 19% for all-polymer OPVs. Second, the delayed crystallization kinetics from solution to film solidification is achieved that gives a longer operation time window for optimized blend morphology in large-area module, thus relieving the loss of fill factor and allowing a record efficiency of 16.26% on an upscaled module with an area of 19.3 cm2 . Besides, this all-polymer system also shows excellent mechanical stability. This work demonstrates that all-polymer ternary systems are capable of solving the upscaled manufacturing issue, thereby enabling high-efficiency OPV modules.

Numerical and Experimental Investigation on Flow Field of the Turbine Stage under Different Axial Gaps

In order to reduce efficiency losses and improve the aerodynamic efficiency of axial turbines used in industry, the flow fields of the turbine stage were investigated numerically and experimentally under different axial gaps in this work. The influence of the axial gaps on the flow unsteadiness and the flow field distribution is discussed. The results show that the aerodynamic efficiency of the turbine stage increases when the axial distance is reduced. The difference in entropy increases under different axial distances are mainly found in the section from the stator inlet to the rotor inlet: the turbine not only has a better time-average aerodynamic performance, but also has a better transient aerodynamic performance under working conditions with a small axial distance. Additionally, the maximum disturbance amplitudes of the stator and rotor are located near the trailing edge of the stator and the leading edge of the rotor, respectively. Compared with the wake disturbance of the upstream stator to the downstream adjacent rotor, the reverse disturbance of the downstream stator to the adjacent upstream rotor is more sensitive to the change in the blade spacing.

Four-terminal perovskite/silicon series solar cells with 28% efficiency achieved by suppressing edge recombination

Although the commercial application of solar cells pursues scalable and large-area devices, small-area solar cells on a scale of several centimeters possess many advantages such as low fabrication cost and facile high-throughput screening in the research laboratory. Most emerging photovoltaic technology starts from the studying of small-area devices. Recently, perovskite/silicon tandem solar cells have aroused extensive research interest because they can break through the radiative efficiency limit of single-junction solar cells. However, when commercial large-area silicon cells are cut into small pieces with a few squared centimeters in area for laboratory use, there occurs a significant efficiency loss, limiting the performance of tandem cells. Herein, to eliminate the thermal damage caused by the traditional laser cutting method and also reduce the non-radiative recombination of heterojunction silicon cells after being cut, a cold-manufacturing method of grinding wheel dicing is used to cut heterojunction silicon cells. This method is realized by high-speed mechanical grinding accompanied by liquid washing, which avoids damaging the edge of solar cell caused by heat. Compared with the device cut by laser, the heterojunction silicon cells cut by the cold-manufacturing method exhibit less cross-sectional damage. The measurements by scanning electron microscopy (SEM) and three-dimensional optical profilometer reveal that the morphology of the device edge is smoother than the counterpart cut by laser. Device physics measurements including electrochemical impedance spectrum(EIS), dark current-voltage curves, transient photovoltage (TPV), transient photocurrent (TPC), and the dependence of short-circuit current density and open-circuit voltage on light intensity reveal that the cold-manufacturing method can significantly prevent the heterojunction silicon cells from non-radiatively recombining after being cut. These results indicate that the edge-recombination of the silicon solar cells cut by grinding wheels is reduced compared with that cut by laser. As a result, statistical analysis of the device performance reveals that both the open-circuit voltage and fill factor of the device are improved, and the average photoelectric conversion efficiency increases by an absolute efficiency of ~1%. Stacking the obtained silicon cells with the normal transparent perovskite solar cells, the obtained four-terminal perovskite/silicon tandem solar cells deliver an efficiency of over 28%. This work emphasizes the importance of reducing efficiency loss during manufacturing the heterojunction silicon solar cell in fabricating high-performance silicon-based tandem solar cells.

3D Network‐Assisted Crystallization for Fully Printed Perovskite Solar Cells with Superior Irradiation Stability

AbstractMeniscus‐coating as a high‐throughput preparation process has significant advantages in the manufacture of large‐area perovskite solar cells (PSCs). However, the gradient crystallization during printing significantly affects the vertical uniformity of perovskite films, which greatly affects the carrier transport of perovskite films and the stability of PSCs. Here, a perovskite ink compatible with printing technology is reported to realize uniform printing of perovskite film on a 3D scale. The siloxane 3D network hinders the solute migration caused by capillary force and acts as a skeleton to promote the uniform crystallization of perovskite films. Consequently, the corresponding fully printed PSCs have reduced efficiency loss (from 37.4% to 17.0%). In addition, based on the improvement of crystal quality and reduction of defects in perovskite films, the siloxane‐optimized PSCs achieved a championship efficiency of 22.0%, which is one of the highest performance for fully printed devices. The optimized device retains 80% of the initial PCE after 800 h AM 1.5G one‐sun illumination, and only decreases 20% after 160 h of ultraviolet light (365 nm, 20 mW cm−2) irradiation.

Efficiency Loss and Intensification Potential of Urban Industrial Land Use in Three Major Urban Agglomerations in China

In recent decades, efficiency and intensification have emerged as hot topics within urban industrial land use (UILU) studies in China. However, the measurement and analysis of UILU efficiency and intensification are not accurate and in-depth enough. The study of UILU efficiency loss and intensification potential and their relationship is still lacking, and the application of parametric methods with clearer causal mechanisms is insufficient. This paper argued that the intensification potential of UILU could be defined as the amount of saved land or output growth resulting from reduced efficiency loss of UILU. Accordingly, we constructed quantitative models for measuring and evaluating the intensification potential of UILU, using the stochastic frontier analysis (SFA) method to calculate efficiency loss in three major urban agglomerations (38 cities) in China. Our results revealed a large scale and an expanding trend in the efficiency loss and intensification potential of UILU in three major urban agglomerations in China. From 2003 to 2016, the annual efficiency loss of UILU was 31.56%, the annual land-saving potential was 979.98 km2, and the annual output growth potential was 8775.23 billion Yuan (referring to the constant price for 2003). It is, therefore, imperative to formulate and implement better policies and measures to promote further intensification and to reduce inefficiency, especially in the Yangtze and Pearl River Deltas and prioritizing a few key cities, such as Dongguan, Shenzhen, and Shanghai.

A new passive PV heatsink design to reduce efficiency losses: A computational and experimental evaluation

The efficiency of photovoltaic systems is decreased when its operating temperature increases, which can affect the performance in arid climatic conditions. In this work, a new passive cooling system for photovoltaic panels is presented, with the aim of reducing its operational temperature and preventing a reduction in its electrical efficiency in unfavorable environments. With this aim, a series of 3D models of heatsinks were designed. The systems were evaluated through simulating normal operational conditions using CFD software. Prototypes of the models with the best performance regarding level and distribution of temperature were built for experimental evaluation. The use of a segmented aluminum sheet was proposed; allowing a better airflow, and therefore, improved cooling under high irradiance conditions. Numerical simulation results showed improved in temperature distribution and a reduction of up to 9.4 °C in the most effective heatsinks. Experimental results were in close agreement, achieving a reduction of around 10 °C during peak irradiance. Results of this work support the use of the integration of PV and passive cooling systems to reduce efficiency losses under real operating conditions, where there is a multidirectional nature of airflow, which may not be favorable for a conventional heatsink with a continuous channel design.

Optimal Disclosure Regulation for Entrepreneurial Public Financing with Post-Financing Moral Hazard

This paper studies optimal disclosure regulation for entrepreneurial public financing with post-financing moral hazard problem. I show that partial disclosure can improve social welfare over full disclosure through reducing efficiency loss caused by the moral hazard problem. As a result, a properly designed partial disclosure rule would be optimal without assuming any disclosure cost. This remains true after allowing for endogenous entrepreneur types with adverse selection concerns. With (constrained) Bayesian persuasion tools, the optimal disclosure rule is fully characterized. Although the paper is developed mainly around entrepreneur equity financing, its intuition can be more generally applicable. For instance, I also adapt the basic model to debt financing and an application to banking system disclosure is provided.

The long‐term extreme price risk measure of portfolio in inventory financing: An application to dynamic impawn rate interval

Different from the short‐term risk measure for traditional financial assets (stocks, bonds, etc.), the key to illiquid inventory portfolio traded in the over‐the‐counter markets is to estimate the long‐term extreme price risk with time varying volatility. In this article, a new long‐term extreme price risk (value at risk and conditional value at risk) measure method for inventory portfolio and an application to dynamic impawn rate interval are proposed. To realize this, we first establish AutoRegressive Moving Average‐Exponential Generalized Autoregressive Conditional Heteroskedasticity‐Extreme Value Theory model and multivariatet‐Copula to depict the autocorrelation, fat tails, and volatility clustering of returns of inventories and the nonlinear dependence structure of inventories. Furthermore, we obtain the long‐term extreme price risk with time varying volatility via Monte Carlo simulation instead of square‐root‐of time rule. The results show that, first, benefits from risk diversification is significant; second, long‐term extreme price risk measure of inventory portfolio via Monte Carlo method outperforms the square‐root‐of time rule; the last is that the dynamic rate interval based on the long‐term price risk is superior to the crude rules of thumb in terms of reducing efficiency loss and improving risk coverage. In summary, this article provides a new quantitative framework for managing the risk of portfolio in inventory financing practice for banks constrained by risk limitation. © 2014 Wiley Periodicals, Inc. Complexity 20: 17–34, 2015

Economic efficiency and social insurance reforms in China

This study discusses efficiency issues related to social insurance provisions and their implications for the newly established three-pillar pension system and three-tier health insurance system in China. It shows that these new systems can be improved substantially through some restructuring to reduce efficiency losses. The discussion of efficiency consequences focuses on correction for market failure and alternative mechanisms for financing and providing social insurance benefits. Alternative methods for financing the transition are also discussed.

Economic efficiency and social insurance reforms in China

This study discusses efficiency issues related to social insurance provisions and their implications for the newly established three‐pillar pension system and three‐tier health insurance system in China. It shows that these new systems can be improved substantially through some restructuring to reduce efficiency losses. The discussion of efficiency consequences focuses on correction for market failure and alternative mechanisms for financing and providing social insurance benefits. Alternative methods for financing the transition are also discussed.

China's power industry, 1980–1990: Price reform and its effect on energy efficiency

We examine the economic reforms in China's electric power industry during the 1980s, describe China's pre-reform economy and show how investment and price reforms affected the power industry. Despite notable gains in economic and energy efficiencies following the introduction of market-oriented policies, some reform measures produced undesirable side-effects for the power industry. Using a simple economic model, it is possible to show that the multiple-price system adopted in the mid-1980s for paying power producers results in the underutilization of China's newest and most energy-efficient plants. We provide an estimate of the fuel losses which may have resulted from this pricing policy and suggest alternative pricing rules which will reduce efficiency losses in the power industry.