| 1. |
- Zhang, Ming, et al.
(author)
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Tethered Small-Molecule Acceptor Refines Hierarchical Morphology in Ternary Polymer Solar Cells: Enhanced Stability and 19% Efficiency
- 2023
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In: Advanced Materials. - : WILEY-V C H VERLAG GMBH. - 0935-9648 .- 1521-4095.
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Journal article (peer-reviewed)abstract
- Polymer solar cells (PSCs) are promising for efficient solar energy conversion, but achieving high efficiency and device longevity within a bulk-heterojunction (BHJ) structure remains a challenge. Traditional small-molecule acceptors (SMAs) in the BHJ blend show thermodynamic instability affecting the morphology. In contrast, tethered SMAs exhibit higher glass transition temperatures, mitigating these concerns. Yet, they might not integrate well with polymer donors, causing pronounced phase separation and overpurification of mixed domains. Herein, a novel ternary device is introduced that uses DY-P2EH, a tethered dimeric SMA with conjugated side-chains as host acceptor, and BTP-ec9, a monomeric SMA as secondary acceptor, which respectively possess hypomiscibility and hypermiscibility with the polymer donor PM6. This unique combination affords a parallel-connected ternary BHJ blend, leading to a hierarchical and stable morphology. The ternary device achieves a remarkable fill factor of 80.61% and an impressive power conversion efficiency of 19.09%. Furthermore, the ternary device exhibits exceptional stability, retaining over 85% of its initial efficiency even after enduring 1100 h of thermal stress at 85 degrees C. These findings highlight the potential advantage of tethered SMAs in the design of ternary devices with a refined hierarchical structure for more efficient and durable solar energy conversion technologies. A ternary-device design is proposed that fully utilizes the individual thermodynamic properties of both dimeric acceptor and monomeric acceptor. The high Tg value of dimeric acceptor significantly impedes the molecular movement of monomeric acceptor, while hypermiscible properties of monomeric acceptor promote percolation of the mixed domain for enhancing charge dynamics.image
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| 2. |
- Bai, Yang, et al.
(author)
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Geometry design of tethered small-molecule acceptor enables highly stable and efficient polymer solar cells
- 2023
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In: Nature Communications. - : NATURE PORTFOLIO. - 2041-1723. ; 14:1
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Journal article (peer-reviewed)abstract
- With the power conversion efficiency of binary polymer solar cells dramatically improved, the thermal stability of the small-molecule acceptors raised the main concerns on the device operating stability. Here, to address this issue, thiophene-dicarboxylate spacer tethered small-molecule acceptors are designed, and their molecular geometries are further regulated via the thiophene-core isomerism engineering, affording dimeric TDY-alpha with a 2, 5-substitution and TDY-beta with 3, 4-substitution on the core. It shows that TDY-alpha processes a higher glass transition temperature, better crystallinity relative to its individual small-molecule acceptor segment and isomeric counterpart of TDY-beta, and amore stablemorphology with the polymer donor. As a result, the TDY-alpha based device delivers a higher device efficiency of 18.1%, and most important, achieves an extrapolated lifetime of about 35000 hours that retaining 80% of their initial efficiency. Our result suggests that with proper geometry design, the tethered small-molecule acceptors can achieve both high device efficiency and operating stability.
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| 5. |
- Shang, Xiangjun, et al.
(author)
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Effect of tunable dot charging on photoresponse spectra of GaAs p-i-n diode with InAs quantum dots
- 2015
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In: Journal of Applied Physics. - Melville, NY : American Institute of Physics (AIP). - 0021-8979 .- 1089-7550. ; 118:24
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Journal article (peer-reviewed)abstract
- Quantum dot (QD)-embedded photodiodes have demonstrated great potential for use as detectors. A modulation of QD charging opens intriguing possibilities for adaptive sensing with bias-tunable detector characteristics. Here, we report on a p-i-n GaAs photodiode with InAs QDs whose charging is tunable due to unintentional Be diffusion and trap-assisted tunneling of holes, from bias-and temperature (T)-dependent photocurrent spectroscopy. For the sub-bandgap spectra, the T-dependent relative intensities "QD-s/WL" and "WL/GaAs" (WL: wetting layer) indicate dominant tunneling under -0.9V (trap-assisted tunneling from the top QDs) and dominant thermal escape under -0.2 similar to 0.5V (from the bottom QDs since the top ones are charged and inactive for optical absorption) from the QD s-state, dominant tunneling from WL, and enhanced QD charging at >190K (related to trap level ionization). For the above-bandgap spectra, the degradation of the spectral profile (especially near the GaAs bandedge) as the bias and T tune (especially under -0.2 similar to 0.2V and at >190 K) can be explained well by the enhanced photoelectron capture in QDs with tunable charging. The dominant spectral profile with no degradation under 0.5V is due to a saturated electron capture in charged QDs (i.e., charging neutralization). QD level simulation and schematic bandstructures can help one understand these effects.
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| 6. |
- Wang, Haiqiao
(author)
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Mini-Jet Production in Proton-Antiproton Interactions and Particle Production in Heavy-Ion Collisions
- 1997
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Doctoral thesis (other academic/artistic)abstract
- The thesis is based on the data analysis and detector development of the EMU01/CERN, E863/BNL and UA1/CERN experiments. Particle fluctuations are studied with the scaled factorial moments in the fragmentation region of oxygen-induced emulsion interactions from 3.7 to 200 A GeV. The intermittency indices show an energy independent behaviour in the target and projectile regions of pseudorapidity. In order to study the origin of the fluctuations, jet-like and ring-like substructures of particles produced in the azimuthal plane are investigated for the S-Au, S-Em and O-Em interactions at 200 A GeV. The study shows that the two-particle azimuthal correlations can be well understood if Bose-Einstein correlations and gamma conversion are included. A nuclear rescattering model, which incorperates the FRITIOF model, has been developed. The model can well describe multiplicity distributions of slow recoiling protons, evaporation particles and their correlations with particles produced in high energy heavy-ion collisions. In the autumn of 1994, truly heavy nuclei (Pb) were accelerated to 158 A GeV/c at the CERN/SPS. In order to improve the measurements of Pb-induced collisions, an automatic system based on the CCD technique and image processing was developed. This system has been used to measure densities of the particles produced. Mini-jet production is studied using the UA1 1987 minimum bias data sample for p bar p interaction at 630 GeV of C.M.S energy. The study shows that the transverse energy distribution of mini-jets is in good agreement with the QCD prediction. The angular distributions of two leading jets show the behaviour of elastic scattering of partons with gluon exchange.
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| 7. |
- Wang, Lijuan, et al.
(author)
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Enhanced tunneling in the GaAs p(+)-n(+) junction by embedding InAs quantum dots
- 2012
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In: Semiconductor Science and Technology. - : IOP Publishing. - 0268-1242 .- 1361-6641. ; 27:11, s. 115010-
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Journal article (peer-reviewed)abstract
- GaAs p(+)-n(+) junctions with and without a layer of InAs quantum dots (QDs) embedded at the interface are discussed in this article. The current density versus voltage (I-V) characteristics show that the junctions without QDs are weak degenerate due to the Beryllium(Be) atoms diffusion of nominal p(++)-GaAs; the junctions with QDs generate enhanced tunneling current at forward bias, because the QDs layer reduces the Be diffusion and enables a two-step tunneling process. At room temperature, the current density of the sample with QDs is enhanced to 122 A cm(-2) at a forward bias of +0.32 V, which is about 2 orders of magnitude higher than the reference sample without QDs.
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