| 1. |
- Choi, Hyeon-Seo, et al.
(author)
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Oriented Crystal Growth during Perovskite Surface Reconstruction
- 2022
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In: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 14:45, s. 51149-51156
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Journal article (peer-reviewed)abstract
- Surface passivation has become a key strategy for an improvement in power conversion efficiency (PCE) of perovskite solar cells (PSCs) since PSCs experienced a steep increase in PCE and reached a comparably matured point. Recently, surface passivation using a mixed salt of fluorinated alkyl ammonium iodide and formamidinium bromide demon-strated a remarkable improvement in both performance and stability, which can be tuned by the length of the alkyl chain. Nevertheless, the role of the alkyl chain in manipulating surface-limited crystal growth was not fully understood, preventing a further progress in interface control. In this study, we found that the length of the fluorine-substituted alkyl chain governed the crystal formation dynamics by manipulating surface tensions of different crystal orientations. The overall enhancement of the (001) plane, being the most favored, commonly resulted from the surface reformation of the perovskite film regardless of the chain length, while the highly oriented (001) over (111) was monitored with a particular chain length. The enhanced crystal orientation during surface recrystallization was responsible for the low trap density and thus effectively suppressed charge recombination at the interface, resulting in a considerable increase in open-circuit voltage and fill factor.
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| 2. |
- Clarke, Andrew J., et al.
(author)
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Non-fullerene acceptor photostability and its impact on organic solar cell lifetime
- 2021
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In: Cell Reports Physical Science. - : Elsevier. - 2666-3864. ; 2:7
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Journal article (peer-reviewed)abstract
- The development of non-fullerene acceptors (NFAs) has facilitated the realization of efficient organic solar cells (OSCs) with minimal burn-in losses and excellent long-term stability. However, the role of NFA molecular structures on device stability remains unclear, limiting commercialization of NFA-based OSCs. Herein, the photostability of 10 OSC devices, fabricated with various NFAs (O-IDTBR, EH-IDTBR, ITIC, and ITIC-M) blended with donor polymers (PTB7-Th, PffBT4T-2OD, and PBDB-T), is investigated. O-IDTBR and EH-IDTBR form highly stable devices with all three polymers, whereas ITIC and ITIC-M devices suffer from burn-in losses and long-term degradation. Conformational instability is found to be responsible for the poor photostability of ITIC and ITIC-M, resulting in poor device stability. Twisting and potential breakage of the chemical bond that links the end group to the main backbone of ITIC and ITIC-M molecules causes undesirable conformational changes. Potential strategies to overcome such detrimental photo-induced conformational changes in NFAs are proposed.
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| 3. |
- Hart, Lucy J. F., et al.
(author)
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Understanding the Role of Triplet-Triplet Annihilation in Non-Fullerene Acceptor Organic Solar Cells
- 2023
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In: Advanced Energy Materials. - : WILEY-V C H VERLAG GMBH. - 1614-6832 .- 1614-6840. ; 13:36
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Journal article (peer-reviewed)abstract
- Non-fullerene acceptors (NFAs) have enabled power conversion efficiencies exceeding 19% in organic solar cells (OSCs). However, the open-circuit voltage of OSCs remains low relative to their optical gap due to excessive non-radiative recombination, and this now limits performance. Here, an important aspect of OSC design is considered, namely management of the triplet exciton population formed after non-geminate charge recombination. By comparing the blends PM6:Y11 and PM6:Y6, it is shown that the greater crystallinity of the NFA domains in PM6:Y11 leads to a higher rate of triplet-triplet annihilation (TTA). This is attributed to the four times larger ground state dipole moment of Y11 versus Y6, which improves the long range NFA out-of-plane ordering. Since TTA converts a fraction of the non-emissive triplet states into bright singlet states, it has the potential to reduce non-radiative voltage losses. Through a kinetic analysis of the recombination processes under 1-Sun illumination, a framework is provided for determining the conditions under which TTA may improve OSC performance. If these could be satisfied, TTA has the potential to reduce non-radiative voltage losses by up to several tens of millivolts.
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| 4. |
- Park, Seoyeon, et al.
(author)
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The global burden of sudden infant death syndrome from 1990 to 2019: a systematic analysis from the Global Burden of Disease study 2019
- 2022
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In: QJM Monthly Journal of the Association of Physicians. - : OXFORD UNIV PRESS. - 1460-2725 .- 1460-2393. ; 115:11, s. 735-744
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Journal article (peer-reviewed)abstract
- Background Sudden infant death syndrome (SIDS) still remains one of the leading causes of infant death worldwide, especially in high-income countries. To date, however, there is no detailed information on the global health burden of SIDS. Aims To characterize the global disease burden of SIDS and its trends from 1990 to 2019 and to compare the burden of SIDS according to the socio-demographic index (SDI). Design Systematic analysis based on the Global Burden of Disease (GBD) 2019 data. Methods Epidemiological data of 204 countries from 1990 to 2019 were collected via various methods including civil registration and vital statistics in the original GBD study. Estimates for mortality and disease burden of SIDS were modeled. Crude mortality and mortality rates per 100 000 population were analyzed. Disability-adjusted life years (DALYs) and DALY rates were also assessed. Results In 2019, mortality rate of SIDS accounted for 20.98 [95% Uncertainty Interval, 9.15-46.16] globally, which was a 51% decrease from 1990. SIDS was most prevalent in Western sub-Saharan Africa, High-income North America and Oceania in 2019. The burden of SIDS was higher in males than females consistently from 1990 to 2019. Higher SDI and income level was associated with lower burden of SIDS; furthermore, countries with higher SDI and income had greater decreases in SIDS burden from 1990 to 2019. Conclusions The burden of SIDS has decreased drastically from 1990 to 2019. However, the improvements have occurred disproportionately between regions and SDI levels. Focused preventive efforts in under-resourced populations are needed.
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| 5. |
- Yan, Hao, et al.
(author)
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Enhancing hole carrier injection via low electrochemical doping on circularly polarized polymer light-emitting diodes
- 2022
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In: Journal of Materials Chemistry C. - : ROYAL SOC CHEMISTRY. - 2050-7526 .- 2050-7534. ; 10:25, s. 9512-9520
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Journal article (peer-reviewed)abstract
- Circularly polarized electroluminescence (CP-EL) from a blend system of chiral small-molecule additives and device optimised achiral pi-conjugated polymers (pi-CPs) is of great interest for next-generation display technologies. However, CP polymer light-emitting diodes can suffer from unbalanced charge transport and unfavorable energetics between chiral additives and achiral polymers, which can limit the efficiency of charge injection and device performance. Herein, we demonstrate the use of a small amount of chemcially modified electrochemical doping agent (EDA, 1.5 wt%) to control such limitations. The EDA with a long cationic alkyl chain enables strong hydrophobicity and stable electrochemical doping of achiral pi-CP F8BT in F8BT:aza[6]H blends, which allows for better charge injection and balance. This leads to improved device performance while maintaining highly dissymmetric electroluminescence (g(EL) similar to 0.50@580 nm) and an inverted dissymmetry factor (g(EL) = -0.65@525 nm). These findings indicate that EDAs may provide a simple approach to improve the performance of CP optoelectronic devices.
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