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Significant nonradiative energy loss and short exciton diffusion length in organic solar cells (OSCs) are two major obstacles to achieving state-of-the-art efficiencies. It is crucial to conduct a study on the intensive mechanism and improvement strategies for future breakthroughs in the efficiency of OSCs. In this work, nonradiative energy loss and exciton diffusion length are optimized simultaneously by incorporating a guest acceptor (LA15) to construct ternary OSC (D18:L8-BO:LA15). Firstly, LA15 exhibits excellent compatibility with the host acceptor L8-BO, and effectively improves the fluorescence quantum efficiency (FLQY), resulting in suppressed non-radiative energy loss. Moreover, LA15 effectively prolongs the fluorescent lifetime of the acceptor phase from 0.85 to 1.12 ns, leading to larger exciton diffusion length, which is beneficial for reducing geminate recombination. Besides, the addition of LA15 optimizes the crystallinity of the active layer with amplified charge transport capacity. As a result, the optimized D18:L8-BO:LA15 device achieves ultralow nonradiative energy loss of 0.18 eV and improved fill factor (FF) with high efficiency up to 19.13%. These results highlight the crucial roles of regulating FLQY and exciton lifetime in achieving high-efficiency OSCs.

Financial market liquidity is a popular research topic. Investor-driven research uses the turnover rate to measure liquidity and generally finds that the higher the stock turnover rate, the lower the returns. However, the traditional financial liquidity theory has been impacted by new machine-driven quantitative trading models. To explore high machine-driven liquidity and the impact of high turnover rates on returns, this study establishes a dual-market quantitative trading system, introduces a variational modal decomposition (VMD)-bidirectional gated recurrent unit (BiGRU) model for data prediction, and uses the back-end Hong Kong foreign exchange market to develop a quantitative trading strategy using the same rotating funds in the U.S. and Chinese stock markets. The experimental results show that given a principal amount of 210,000.00 CNY, the final predicted net return is 226,538.30 CNY, a net return of 107.86%, which is 40.6% higher than the net return of a single Chinese market. We conclude that, under machine-driven trading, increasing liquidity and turnover increase returns. This study provides a new perspective on liquidity theory that is useful for future financial market research and quantitative trading practices.

AbstractThis study investigates the efficiencies of the exchange markets for four major currencies—the euro (EUR), the pound (GBP), the Canadian dollar (CAD) and the Japanese yen (JPY)—from 2005 to 2019 by using multifractal detrended fluctuation analysis (MF-DFA). This study also investigates the causes of these efficiencies. Significant multifractal properties are demonstrated by the four markets, and long-range correlation and fat-tail distribution properties are the main causes. We calculate and compare the multifractal degrees in three subsamples, which are classified based on their temporal relation to two economic events: the 2008 financial crisis and the announcement by the Federal Reserve of its withdrawal from the quantitative easing policy in 2014. Empirical results suggest that multifractal properties exist at different levels in the subsamples, thus showing that these events affect foreign exchange market efficiencies in terms of statistics and the fractal market. The JPY exchange market has the fewest multifractal properties, thus indicating that this exchange market has the highest market efficiency among these four exchange markets. The empirical results have implications for the nonlinear mechanism and efficiency in foreign exchange markets, which may help investors effectively manage market risks and benefit a stable global economy.

To clearly show how important the impact of side chains on organic solar cells (OSCs) is, we designed three acceptors IDIC-CxPh (x = 4, 5, or 6) via subtle side-chain regulation. Despite this small change, significant distinctions were detected. IDIC-C4Ph devices achieve an optimal efficiency of 13.94% under thermal annealing, but thermal-assistant solvent-vapor annealing hugely suppresses the efficiencies to 10%. However, the C6Ph side chain endows extremely disordered stacking orientations, generating moderate efficiencies of ∼12.50%. Excitingly, the IDIC-C5Ph affords an unexpected two-channel π-π charge transport (TCCT) property, boosting the fill factor (FF) by up to 80.02% and efficiency to 14.56%, ranking the best among five-ring fused-ladder-type acceptors. Impressively, the special TCCT behavior of IDIC-C5Ph enables 470 nm thick-film OSC with a high FF of up to 70.12% and efficiency of 13.01%, demonstrating the great promise in fabricating large-scale OSCs.