Browsing by Author "Wang, Pei-Chun"

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Highly efficient flexible organic light-emitting diodes based on a high-temperature durable mica substrate
(2019-12-01)
Lai, Yi-Ning
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Chang, Chih-Hao
;
Wang, Pei-Chun
;
Chu, Ying-Hao
;
交大名義發表
Muscovite mica is expected to show great potential in flexible optoelectronics due to its superb temperature tolerance, high transmittance, chemical stability, and mechanical durability. This flexible substrate produces sputtered transparent conducing electrodes (TCEs) with excellent film quality with high transmittance and conductivity. In this study, a designed composite TCE consisting of aluminum-doped zinc oxide (AZO) and indium fin oxide (ITO) is proposed to simultaneously maximize flexibility and conductivity. Blue-, green-, and red-emitting flexible organic light-emitting diodes (FOLEDs) using composite TCEs on mica exhibited satisfactory performance with maximum respective electroluminescence efficiencies of 18.1% (38.7 cd/A), 18.7% (66.2 cd/A), and 13.3% (22.2 cd/A). Furthermore, the green-emitting FOLEDs were modified to construct tandem FOLEDs, giving a higher peak efficiency of 27.9% (93.3 cd/A) and saturated green emission. These results can serve as a useful reference for future work on composite TCEs on mica for FOLEDs in display and lighting applications.
Highly flexible, robust, stable and high efficiency perovskite solar cells enabled by van der Waals epitaxy on mica substrate
(2019-06-01)
Jia, Chunmei
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Zhao, Xingyu
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Lai, Yu-Hong
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Zhao, Jinjin
;
Wang, Pei-Chun
Flexible and lightweight solar cells are promising for numerous emerging applications, and organometallic halide perovskites are particularly suitable for flexible solar cell applications. Transferring state of art high efficiency perovskite solar cells (PSCs) processing onto a flexible substrate, however, is challenging, requiring substantial redevelopment of materials compositions, device architectures, and processing conditions. In this work, highly flexible, robust, stable, and high efficiency PSCs based on mica substrate have been successfully developed, exhibiting a champion photovoltaic conversion efficiency (PCE) of 18.0%, retaining more than 91.7% of the original PCE after 5000 cycles of large deformation bending, and being relatively stable against humidity under elevated temperature. Key to such excellent performance is the inorganic and transparent mica substrate that is chemically inert and stable under high temperature, so that processing developed for glass-based high efficiency perovskite solar cells (PSCs) can be readily applied without modification. Furthermore, the layered mica substrate is highly flexible, and van der Waals epitaxial growth of transparent conducing ITO relaxes the mechanical constraint on the PSCs substantially, reducing the strain in the device even under large bending deformation. We believe inorganic flexible mica substrate can be used as a platform for high efficiency PSCs compatible to glass substrate, speeding up the development of flexible PSCs substantially.
Tunable disorder and localization in the rare-earth nickelates
(2019-05-02)
Wang, Changan
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Chang, Ching-Hao
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Huang, Angus
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Wang, Pei-Chun
;
Wu, Ping-Chun
We demonstrate that transport in metallic rare-earth nickelates can be engineered by directly tuning the electronic mean free path. Using irradiation as a tool to induce disorder, we drive this system from a metallic phase into an Anderson insulator. This proceeds via an intermediate regime which shows a thermal crossover from insulating to metallic behavior. We argue that this phase falls within the paradigm of weak localization in three dimensions. We develop a theoretical model for the temperature dependence of resistivity which shows good agreement with our data. The three-dimensional weak localization picture is supported by magnetoconductivity, which scales as similar to B-2 up to several tesla. Interestingly, our data indicate that this phase lies in the Mott-Ioffe-Regel regime with the mean free path approaching the lattice constant. Upon further increasing disorder, the charge carriers are localized, leading to insulating behavior at all temperatures. Our results show that irradiation provides a "clean" tuning knob for the mean free path, without altering other system parameters. This suggests promising directions for studies of Anderson localization.