| 1. |
- Fu, Huiting, et al.
(författare)
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High Efficiency (15.8%) All-Polymer Solar Cells Enabled by a Regioregular Narrow Bandgap Polymer Acceptor
- 2021
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Ingår i: Journal of the American Chemical Society. - : AMER CHEMICAL SOC. - 0002-7863 .- 1520-5126. ; 143:7, s. 2665-2670
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Tidskriftsartikel (refereegranskat)abstract
- Y Despite the significant progresses made in all-polymer solar cells (all-PSCs) recently, the relatively low short-circuit current density (J(sc)) and large energy loss are still quite difficult to overcome for further development. To address these challenges, we developed a new class of narrow-bandgap polymer acceptors incorporating a benzotriazole (BTz)-core fused-ring segment, named the PZT series. Compared to the commonly used benzothiadiazole (BT)-containing polymer PYT, the less electron-deficient BTz renders PZT derivatives with significantly red-shifted optical absorption and up-shifted energy levels, leading to simultaneously improved J(sc) and open-circuit voltage in the resultant all-PSCs. More importantly, a regioregular PZT (PZT-gamma) has been developed to achieve higher regiospecificity for avoiding the formation of isomers during polymerization. Benefiting from the more extended absorption, better backbone ordering, and more optimal blend morphology with donor component, PZT-gamma-based all-PSCs exhibit a record-high power conversion efficiency of 15.8% with a greatly enhanced J(sc) of 24.7 mA/cm(2) and a low energy loss of 0.51 eV.
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| 2. |
- He, Zonglong, 1994, et al.
(författare)
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12.2 bit/s/Hz C-band Transmission with High-Gain Low-Complexity 24-Dimensional Geometric Shaping
- 2024
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Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; In Press
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Tidskriftsartikel (refereegranskat)abstract
- Multidimensional (MD) modulation formats enable a larger minimum Euclidean distance than conventional two-dimensional formats. As a structured geometric shaping method, MD Voronoi constellations (VCs) avoid the use of look-up tables and can be implemented with low-complexity encoding and decoding algorithms, outperforming quadrature amplitude modulation (QAM) formats in terms of mutual information. However, it is challenging to maintain the shaping gain in a practical system requiring bit-mapping and forward error correction (FEC) coding. By using a hybrid labeling and multilevel coding scheme integrated with soft-decision FEC coding, MD VCs can achieve high shaping gain compared to QAM formats after soft-decision (SD) decoding. In practical systems, transceiver impairments significantly degrade the system performance, especially for high-cardinality constellations. To investigate of performance of high spectral-efficiency (SE) MD VCs, we employ a 24-dimensional (24D) VC with uncoded SE of 8 bit/symbol/dimension-pair to a spectral superchannel spanning the full C-band. Specifically, the 24D VC with a record constellation size of 7.9×10 28 is applied to dual-polarization coherent transmission over six time slots. The superchannel is composed of 5.0 Gbaud channels spaced at 5.2 GHz, resulting in an overall spectral efficiency of 12.2 bit/s/Hz and a net throughput of 54.2 Tb/s over the entire C-band after 40 km single-mode fiber. It is the first experimental demonstration of a high-SE MD format providing a significant shaping gain after SD decoding.
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| 3. |
- Mirani, Ali, 1992, et al.
(författare)
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Comparison of Physical Realizations of Multidimensional Voronoi Constellations in Single Mode Fibers
- 2022
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Ingår i: European Conference on Optical Communication, ECOC.
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Konferensbidrag (refereegranskat)abstract
- We investigate experimentally and numerically the impact of using different fiber dimensions to spread out the 32-dimensional Voronoi constellations. We find similar performance in experiments and less than 5.4% reach improvements in long-haul transmission simulations by spreading the constellation dimensions over time slots compared to wavelengths
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| 4. |
- Mirani, Ali, 1992, et al.
(författare)
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Experimental Demonstration of 8-Dimensional Voronoi Constellations with 65,536 and 16,777,216 Symbols
- 2021
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Ingår i: 2021 European Conference on Optical Communication, ECOC 2021. - 9781665438681
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Konferensbidrag (refereegranskat)abstract
- We experimentally demonstrate high-cardinality, low-complexity Voronoi constellations based on the E8 lattice over multiple time slots with OSNR and launch power gains of up to 1.7 and 2.4 dB for back-to-back and 80 km fiber transmission, respectively, compared to QAM formats.
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| 5. |
- Mirani, Ali, 1992, et al.
(författare)
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Physical Realizations of Multidimensional Voronoi Constellations in Optical Communication Systems
- 2023
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Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 41:17, s. 5557-5563
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Tidskriftsartikel (refereegranskat)abstract
- Abstract:Multidimensional geometric shaping has been shown to outperform uniform quadrature amplitude modulation (QAM) in optical communication systems but the complexity of symbol decision and bit mapping can often be significant as dimensionality increases. In this paper, a low-complexity geometric shaping method based on multidimensional lattices is investigated both in experiments and simulations. The modulation formats designed based on this method are called Voronoi constellations (VCs) and we study them in 8, 16, and 32 dimensions. We obtain transmission reach improvements of up to 22 and 70% for VCs compared to 4QAM and 16QAM, respectively, in nonlinear long-haul fiber transmission. Moreover, we compare different physical realizations of multidimensional VCs over wavelengths, polarizations, and time slots in both the Gaussian and nonlinear fiber channels. We demonstrate that different physical realizations perform similarly in the fiber-optic back-to-back channel. However, in long-haul transmission systems, spreading the dimensions over time slots can increase the transmission reach up to 4% compared to wavelengths and polarizations. Furthermore, the mutual information and generalized mutual information are estimated and compared to QAM formats at the same spectral efficiencies.
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| 6. |
- Pan, Qinying, et al.
(författare)
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Ultrafast charge transfer dynamics in 2D covalent organic frameworks/Re-complex hybrid photocatalyst
- 2022
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 13:1
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Tidskriftsartikel (refereegranskat)abstract
- Rhenium(I)-carbonyl-diimine complexes have emerged as promising photocatalysts for carbon dioxide reduction with covalent organic frameworks recognized as perfect sensitizers and scaffold support. Such Re complexes/covalent organic frameworks hybrid catalysts have demonstrated high carbon dioxide reduction activities but with strong excitation energy-dependence. In this paper, we rationalize this behavior by the excitation energy-dependent pathways of internal photo-induced charge transfer studied via transient optical spectroscopies and time-dependent density-functional theory calculation. Under band-edge excitation, the excited electrons are quickly injected from covalent organic frameworks moiety into catalytic RheniumI center within picosecond but followed by fast backward geminate recombination. While under excitation with high-energy photon, the injected electrons are located at high-energy levels in RheniumI centers with longer lifetime. Besides those injected electrons to RheniumI center, there still remain some long-lived electrons in covalent organic frameworks moiety which is transferred back from RheniumI. This facilitates the two-electron reaction of carbon dioxide conversion to carbon monoxide.
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| 7. |
- Xu, Bo, et al.
(författare)
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4-Tert-butylpyridine Free Organic Hole Transporting Materials for Stable and Efficient Planar Perovskite Solar Cells
- 2017
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Ingår i: Advanced Energy Materials. - : Wiley. - 1614-6832 .- 1614-6840. ; 7:19
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Tidskriftsartikel (refereegranskat)abstract
- 4-Tert-butylpyridine (tBP) is an important additive in triarylamine-based organic hole-transporting materials (HTMs) for improving the efficiency and steady-state performance of perovskite solar cells (PVSCs). However, the low boiling point of tBP (196 degrees C) significantly affects the long-term stability and device performance of PVSCs. Herein, the design and synthesis of a series of covalently linked Spiro[fluorene-9,9'-xanthene] (SFX)-based organic HTMs and pyridine derivatives to realize efficient and stable planar PVSCs are reported. One of the tailored HTMs, N2, N2, N7, N7-tetrakis(4-methoxyphenyl)-3', 6'bis( pyridin-4-ylmethoxy) spiro[fluorene-9,9'-xanthene]-2,7-diamine (XPP) with two para-position substituted pyridines that immobilized on the SFX core unit shows a high power conversion efficiency (PCE) of 17.2% in planar CH3NH3PbI3-based PVSCs under 100 mW cm(-2) AM 1.5G solar illumination, which is much higher than the efficiency of 5.5% that using the well-known 2,2', 7,7'-tetrakis-(N, N-di-p-methoxy-phenyl-amine) 9,9'-spirobifluorene (SpiroOMeTAD) as HTM (without tBP) under the same condition. Most importantly, the pyridine-functionalized HTM-based PVSCs without tBP as additive show much better long-term stability than that of the state-of-the-art HTM SpiroOMeTAD- based solar cells that containing tBP as additive. This is the first case that the tBP-free HTMs are demonstrated in PVSCs with high PCEs and good stability. It paves the way to develop highly efficient and stable tBP-free HTMs for PVSCs toward commercial applications.
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