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"Tan, Shaun"
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Three stories explore how we lose and find what matters most to us, as a girl finds a bright spot in a dark world, a boy leads a strange, lost being home, and a group of peaceful creatures loses its home to cruel invaders.
Book
Oriented nucleation in formamidinium perovskite for photovoltaics
The black phase of formamidinium lead iodide (FAPbI
3
) perovskite shows huge promise as an efficient photovoltaic, but it is not favoured energetically at room temperature, meaning that the undesirable yellow phases are always present alongside it during crystallization
1
–
4
. This problem has made it difficult to formulate the fast crystallization process of perovskite and develop guidelines governing the formation of black-phase FAPbI
3
(refs.
5
,
6
). Here we use in situ monitoring of the perovskite crystallization process to report an oriented nucleation mechanism that can help to avoid the presence of undesirable phases and improve the performance of photovoltaic devices in different film-processing scenarios. The resulting device has a demonstrated power-conversion efficiency of 25.4% (certified 25.0%) and the module, which has an area of 27.83 cm
2
, has achieved an impressive certified aperture efficiency of 21.4%.
The black phase of formamidinium lead iodide perovskite is used to make highly efficient solar cells, and a technique to improve its purity and stability by controlling crystal nucleation could make them even better.
Journal Article
قوانين الصيف
يعد هذا الكتاب قوانين الصيف وهي قصة مخصصة للأطفال تستهدف الطفولة المبكرة وتعمل على اسثمار الطفل في بناء المهارات المختلفة المرتبطة بالخيال والابتكار وقوة الشخصية والبحث عن حلول إبداعية وتستمد الطفل الكثير من العلم والمعرفة والمعلومات يعد هذا الكتاب من المنهج السلوكي التربوي رائع يعلم الطفل كيف يستخلص من مشكلاته وكيف يبني شخصيته بشكل مميز ويعطي المربي حلولا لحل مشكلات ابنه تعنيه عن تجاوز الأزمة وإنهائها.
Book
Constructive molecular configurations for surface-defect passivation of perovskite photovoltaics
Surface trap–mediated nonradiative charge recombination is a major limit to achieving high-efficiency metal-halide perovskite photovoltaics. The ionic character of perovskite lattice has enabled molecular defect passivation approaches through interaction between functional groups and defects. However, a lack of in-depth understanding of how the molecular configuration influences the passivation effectiveness is a challenge to rational molecule design. Here, the chemical environment of a functional group that is activated for defect passivation was systematically investigated with theophylline, caffeine, and theobromine. When N-H and C=O were in an optimal configuration in the molecule, hydrogen-bond formation between N-H and I (iodine) assisted the primary C=O binding with the antisite Pb (lead) defect to maximize surface-defect binding. A stabilized power conversion efficiency of 22.6% of photovoltaic device was demonstrated with theophylline treatment.
Journal Article
سيكادا
من الحالم شون تان، قصة ملهمة لقراء الكتب المصورة الأكبر سنا وغيرهم يروي السيكادا قصة زيز صغير مجتهد لا يحظى بالتقدير على الإطلاق لما يفعله، لكن في النهاية، فقط عندما تعتقد أنه استسلم، يقوم بالتحول إلى شيء جميل بشكل لا يوصف، استعارة للنمو ؟ القليل من الإلهام للجاهد غير المقدر فينا جميعا ؟ ربما كل ذلك وأكثر من ذلك.
Book
Perovskite-polymer composite cross-linker approach for highly-stable and efficient perovskite solar cells
Manipulation of grain boundaries in polycrystalline perovskite is an essential consideration for both the optoelectronic properties and environmental stability of solar cells as the solution-processing of perovskite films inevitably introduces many defects at grain boundaries. Though small molecule-based additives have proven to be effective defect passivating agents, their high volatility and diffusivity cannot render perovskite films robust enough against harsh environments. Here we suggest design rules for effective molecules by considering their molecular structure. From these, we introduce a strategy to form macromolecular intermediate phases using long chain polymers, which leads to the formation of a polymer-perovskite composite cross-linker. The cross-linker functions to bridge the perovskite grains, minimizing grain-to-grain electrical decoupling and yielding excellent environmental stability against moisture, light, and heat, which has not been attainable with small molecule defect passivating agents. Consequently, all photovoltaic parameters are significantly enhanced in the solar cells and the devices also show excellent stability.
Defective grain boundaries of polycrystalline perovskite films are one of the major causes of the instability of the solar cell devices. Here Han et al. choose a polymer with proper molecular structure to crosslink the perovskite grains to greatly improve the device stability.
Journal Article
Cicada
Cicada work in tall building. Data entry clerk. Seventeen year. No sick day. No mistake. Tok Tok Tok! Cicada works in an office, dutifully working day after day for unappreciative bosses and being bullied by his co-workers. But one day, something truly extraordinary happens.
Book
Cross-reactivity of SARS-CoV-2 with HIV chemiluminescent assay leading to false-positive results
Correspondence to Dr Shaun S Tan, National University Hospital, Singapore 119074, Singapore; shaun_sy_tan@nuhs.edu.sg HIV may be considered as a differential diagnosis for patients who present with prolonged fever and respiratory symptoms. Liu and colleagues had previously demonstrated the susceptibility of fourth-generation p24 HIV antigen/antibody tests to false positivity from an array of pathogens, including that of Epstein-Barr virus and metastatic cancer.2 Other centres have also reported interfering substances such as rheumatoid factor, anti-hepatitis C virus, liver cirrhosis and autoimmune disease.3 Further, although literature has reported specificity of HIV chemiluminescent immunoassays to be 99% or better, clinicians should be cognizant to the fact that discordant COVID-19 and HIV results necessitate professional laboratory consult in view of potential analytical error, where patient safety may be compromised if treatment is initiated prematurely.4 The limitation of our report is that the patients’ attending physicians had not sent a sample for HIV nucleic acid testing, which would be definitive. Multicenter evaluation of a new automated fourth-generation human immunodeficiency virus screening assay with a sensitive antigen detection module and high specificity.
Journal Article
Tales from the inner city
A collection of illustrated short stories, each one about the relationship of humans and the animals, both wild and domestic, that share the urban environment of the inner city.
Book
Practical laboratory considerations amidst the COVID-19 outbreak: early experience from Singapore
The coronavirus disease 2019 (COVID-19) is a zoonotic viral infection originating from Wuhan, China in December 2019. The World Health Organization has classified this pandemic as a global health emergency due to its virulent nature of transmission, which may lead to acute respiratory distress syndrome. Singapore’s health ministry has responded with enhanced surveillance of COVID-19 for all suspected pneumonia cases, further increasing the volume of testing via real-time reverse transcription PCR, as well as samples necessitating stringent infectious control. Collectively, this has implications on the total testing process, laboratory operations and its personnel due to biosafety concerns. Turnaround time for routine testing may also be affected. The aim of this article is to present our tertiary institution’s early experience with managing this emerging crisis and offer practical considerations for the preanalytical, analytical and postanalytical phases of laboratory testing in this cohort of patients.
Journal Article