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Your search keyword '"Tsang, Sai‐Wing"' showing total 419 results
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419 results on '"Tsang, Sai‐Wing"'

2. Intermolecular CT excitons enable nanosecond excited-state lifetimes in NIR-absorbing non-fullerene acceptors for efficient organic solar cells

Author

Chen, Xian-Kai, Chan, Christopher C. S., Mahadevan, Sudhi, Guo, Yu, Zhang, Guichuan, Yan, He, Wong, Kam Sing, Yip, Hin-Lap, Bredas, Jean-Luc, Tsang, Sai Wing, and Chow, Philip C. Y.

Subjects
Physics - Chemical Physics
Abstract

State-of-the-art Y6-type molecular acceptors exhibit nanosecond excited-state lifetimes despite their low optical gaps (~1.4 eV), thus allowing organic solar cells (OSCs) to achieve highly efficient charge generation with extended near-infrared (NIR) absorption range (up to ~1000 nm). However, the precise molecular-level mechanism that enables low-energy excited states in Y6-type acceptors to achieve nanosecond lifetimes has remained elusive. Here, we demonstrate that the distinct packing of Y6 molecules in film leads to a strong intermolecular charge-transfer (iCT) character of the lowest excited state in Y6 aggregates, which is absent in other low-gap acceptors such as ITIC. Due to strong electronic couplings between the adjacent Y6 molecules, the iCT-exciton energies are greatly reduced by up to ~0.25 eV with respect to excitons formed in separated molecules. Importantly, despite their low energies, the iCT excitons have reduced non-adiabatic electron-vibration couplings with the electronic ground state, thus suppressing non-radiative recombination and allowing Y6 to overcome the well-known energy gap law. Our results reveal the fundamental relationship between molecular packing and nanosecond excited-state lifetimes in NIR-absorbing Y6-type acceptors underlying the outstanding performance of Y6-based OSCs.

Published
2023

15. Temperature-dependent charge transport measurements unveil morphological insights in non-fullerene organic solar cells.

Author

Zhang, Chujun, Feng, Erming, Gao, Yaxin, Wong, Vox Kalai, Li, Hengyue, Liu, Biao, Mahadevan, Sudhi, Tsang, Sai-Wing, Yang, Junliang, and So, Shu Kong

Subjects
ORGANIC thin films, ORDER-disorder transitions, QUANTUM chemistry, SOLAR cells, CHARGE measurement
Abstract

The morphological analysis of bulk heterojunction (BHJ) active layer stands as a critical imperative for advancing the performance of future organic solar cells. Conventional characterization tools employed for morphological investigation often require substantial resources, both in cost and physical space, thereby imposing restraints on research endeavors in this domain. Here, we extend the application of charge carrier transport characterization beyond conventional mobility assessments, utilizing it as a table-top method for preliminary morphological screening in organic thin films. The investigation focuses on several high-performance BHJ systems that utilize typical "Y" non-fullerene acceptors. It involves in-depth transport studies, including temperature- and field-dependent transport characterizations. The resulting transport data are analyzed in detail using the Gaussian disorder model to extract key transport parameters, specifically the high-temperature limited mobility (μ∞) and positional disorder (∑). Integrating these transport parameters with morphological insights obtained through various characterization tools—including x-ray scattering, sensitive spectroscopy, and quantum chemistry simulation—provides a deep understanding of the intricate interplay between charge transport properties and morphological characteristics. The results reveal explicit relationships, associating μ∞ with the degree of molecular stacking in BHJs and ∑ with the structural disorder in molecule skeleton. Our findings point to the promising potential of utilizing a simple transport characterization technique for the early stage evaluation of thin film packing and geometric properties of organic materials. [ABSTRACT FROM AUTHOR]

Published
2024
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27. OLED Optics

Author

Youn, Wooram, Tsang, Sai-Wing, So, Franky, Karlicek, Robert, editor, Sun, Ching-Cherng, editor, Zissis, Georges, editor, and Ma, Ruiqing, editor

Published
2017
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36. Selective Surface Engineering of Perovskite Microwire Arrays

Author

Li, Dengji, primary, Meng, You, additional, Zhang, Yuxuan, additional, Xie, Pengshan, additional, Zeng, Zixin, additional, Wang, Wei, additional, Lai, Zhengxun, additional, Wang, Weijun, additional, Tsang, Sai‐Wing, additional, Wang, Fei, additional, Liu, Chuntai, additional, Lan, Changyong, additional, Yip, SenPo, additional, and Ho, Johnny C., additional

Published
2023
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40. Precursor engineering enables high-performance all-inorganic CsPbIBr2perovskite solar cells with a record efficiency approaching 13%

Author

Chang, Qingyan, An, Yidan, Cao, Huaiman, Pan, Yuzhen, Zhao, Liangyu, Chen, Yulong, We, Yi, Tsang, Sai-Wing, Yip, Hin-Lap, Sun, Licheng, and Yu, Ze

Abstract

A triple-component precursor (TCP) system is developed for the fabrication of highly uniform and compact CsPbIBr2perovskite films with enlarged film thicknesses, and thus enhanced light absorption capability. Perovskite solar cells (PSCs) based on the resultant CsPbIBr2films afford a champion efficiency of 12.8%, which is the record efficiency reported for CsPbIBr2PSCs.

Published
2024
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43. Hydrogen-bond-bridged intermediate for perovskite solar cells with enhanced efficiency and stability

Author

Li, Fengzhu, Deng, Xiang, Shi, Zhangsheng, Wu, Shengfan, Zeng, Zixin, Wang, Deng, Li, Yang, Qi, Feng, Zhang, Zhuomin, Yang, Zhengbao, Jang, Sei-Hum, Lin, Francis R., Tsang, Sai-Wing, Chen, Xian-Kai, Jen, Alex K.-Y., Li, Fengzhu, Deng, Xiang, Shi, Zhangsheng, Wu, Shengfan, Zeng, Zixin, Wang, Deng, Li, Yang, Qi, Feng, Zhang, Zhuomin, Yang, Zhengbao, Jang, Sei-Hum, Lin, Francis R., Tsang, Sai-Wing, Chen, Xian-Kai, and Jen, Alex K.-Y.

Abstract

Improving the intrinsic film quality of metal halide perovskites is very critical to increase the power conversion efficiency and long-term stability of perovskite solar cells. Here we report a multifunctional, non-volatile additive that can be used to modulate the kinetics of perovskite film growth through a hydrogen-bond-bridged intermediate phase. The additive enables the formation of large perovskite grains and coherent grain growth from bottom to the surface of the film. The enhanced film morphology results in significantly reduced non-radiative recombinations, thus boosting the power conversion efficiency of inverted (p–i–n) solar cells to 24.8% (24.5% certified) with a low energy loss of 0.36 eV. The unencapsulated devices exhibit improved thermal stability with a T98 lifetime beyond 1,000 h under continuous heating at 65 ± 5 °C in a nitrogen-filled glovebox. This effective approach can also be applied to wide-bandgap perovskites and large-area devices to show reduced voltage loss and high efficiency. © 2023, The Author(s), under exclusive licence to Springer Nature Limited.

Published
2023

45. On the Ion Coordination and Crystallization of Metal Halide Perovskites by In Situ Dynamic Optical Probing.

Author

Zeng, Zixin, Wang, Yunfan, Xie, Yue‐Min, Zhu, Zhaohua, Yang, Yajie, Ma, Yuhui, Hao, Xia, Lee, Chun‐Sing, Cheng, Yuanhang, and Tsang, Sai‐Wing

Subjects
PEROVSKITE, METAL halides, ANNEALING of metals, CRYSTALLIZATION, CRYSTAL growth, SURFACE passivation, LASER-induced fluorescence
Abstract

Controlling the crystallization to achieve high‐quality homogeneous perovskite film is the key strategy in developing perovskite electronic devices. Here, an in situ dynamic optical probing technique is demonstrated that can monitor the fast crystallization of perovskites and effectively minimize the influence of laser excitation during the measurement. This study finds that the typical static probing technique would damage and induce phase segregation in the perovskite films during the excitation. These issues can be effectively resolved with the dynamic probing approach. It also found that the crystallization between MAPbI3 and MAPbI2Br is strikingly different. In particular, MAPbI2Br suffers from inefficient nucleation during the spin‐coating that strongly affects the uniform crystal growth in the annealing process. The commonly used pre‐heating process is found at a lower temperature not only can further promote the nucleation but also to complete the crystallization of MAPbI2Br. The role of further annealing at a higher temperature is to facilitate ion‐dissociation on the crystal surface to form a passivation layer to stabilize the MAPbI2Br lattices. The device performance is strongly correlated with the film formation mechanism derived from the in situ results. This work demonstrates that the in situ technique can provide deep insight into the crystallization mechanism, and help to understand the growth mechanism of perovskites with different compositions and dimensionalities. [ABSTRACT FROM AUTHOR]

Published
2024
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46. Hydrogen-bond-bridged intermediate for perovskite solar cells with enhanced efficiency and stability

Author

Li, Fengzhu, primary, Deng, Xiang, additional, Shi, Zhangsheng, additional, Wu, Shengfan, additional, Zeng, Zixin, additional, Wang, Deng, additional, Li, Yang, additional, Qi, Feng, additional, Zhang, Zhuomin, additional, Yang, Zhengbao, additional, Jang, Sei-Hum, additional, Lin, Francis R., additional, Tsang, Sai‐Wing, additional, Chen, Xian-Kai, additional, and Jen, Alex K.-Y., additional

Published
2023
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