Organic additive engineering toward efficient perovskite light‐emitting diodes

Perovskite materials with excellent optical and electrical properties are promising for light‐emitting diodes. In the field of perovskite light‐emitting diodes (PeLEDs), organic materials additive engineering has been proved to be an effective scheme for enhancing efficiency and stability in PeLEDs. Most impressively, the reported external quantum efficiency of PeLEDs based on perovskite‐organic composite has reached over 20%. Herein, we will review the important progress of the organic materials\u27 additive‐modified PeLEDs and discuss the remaining problems and challenges and the key research direction in the near future

Posttraumatic stress on Chinese adolescents’ posttraumatic growth: The role of trauma centrality and emotion regulation

The current 6-month follow-up study investigated 1) the relationship between posttraumatic stress disorder (PTSD) at baseline (T1), trauma centrality and two types of cognitive emotion regulation (CER) at 3-month follow-up (T2), and psychiatric co-morbidity and posttraumatic growth (PTG) at 6-month follow-up (T3), 2) whether trauma centrality at T2 would mediate the impact of initial PTSD on psychiatric co-morbidity and PTG at T3, and 3) whether the two types of CER at T2 (i.e., adaptive CER and maladaptive CER) would respectively mediate the effect of initial PTSD on psychiatric co-morbidity and PTG at T3. Seven hundred and fifty-seven traumatized Chinese adolescents (Male = 400, Female = 357) from two secondary schools participated in the study and completed a demographic page, the Posttraumatic Stress Disorder Checklist for DSM-5, the Centrality of Events Scale, the Posttraumatic Growth Inventory, the General Health Questionnaire-28, the Cognitive Emotion Regulation Questionnaire, and the Educational Stress Scale for Adolescents. After controlling for demographic variables and academic stress, PTSD at baseline was positively associated with trauma centrality at T2, two types of CER at T2, and PTG at T3, but negatively related to psychiatric co-morbidity at T3. Trauma centrality at T2 did not mediate the impact of initial PTSD on psychiatric co-morbidity and PTG at T3. Both types of cognitive emotion regulation at T2 (i.e., adaptive CER and maladaptive CER) respectively mediated the effect of initial PTSD on PTG at T3 and but not that on psychiatric co-morbidity at T3. Following past trauma, Chinese adolescents might experience psychological distress as well as positive changes over time. These traumatic outcomes could be affected by adolescents’ thinking patterns about trauma, as opposed to by their concept of self. Adaptive thinking patterns promoted the positive effect of trauma onto personal growth, whereas the maladaptive patterns impaired the development of growth

Understanding and Specifying Social Access Control Lists

Online social network (OSN) users upload millions of pieces of contenttoshare with otherseveryday. While asignificant portionofthiscontentis benign(andistypicallysharedwith all friends or all OSN users), there are certain pieces of content that are highly privacy sensitive. Sharing such sensitive content raises significant privacy concerns for users, and it becomes important for the user to protect this content from being exposed to the wrong audience. Today, most OSN services provide fine-grained mechanisms for specifying social access control lists (social ACLs, or SACLs), allowing users to restrict their sensitive content to a select subset of their friends. However, it remains unclear how these SACL mechanisms are used today. To design better privacy management tools for users, we need to first understand the usage and complexity of SACLs specified by users. In this paper, we present the first large-scale study of finegrained privacy preferences of over 1,000 users on Facebook, providing us with the first ground-truth information on how users specify SACLs on a social networking service. Overall, we find that a surprisingly large fraction (17.6%) of content is shared with SACLs. However, we also find that the SACL membership shows little correlation with either profile information or social network links; as a result, it is difficult to predict the subset of a user’s friends likely to appear in a SACL. On the flip side, we find that SACLs are often reused, suggesting that simply making recent SACLs available to users is likely tosignificantly reduce the burdenof privacy management on users. 1

Additives in metal halide perovskite films and their applications in solar cells

The booming growth of organic-inorganic hybrid lead halide perovskite solar cells have made this promising photovoltaic technology to leap towards commercialization. One of the most important issues for the evolution from research to practical application of this technology is to achieve high-throughput manufacturing of large-scale perovskite solar modules. In particular, realization of scalable fabrication of large-area perovskite films is one of the essential steps. During the past ten years, a great number of approaches have been developed to deposit high quality perovskite films, to which additives are introduced during the fabrication process of perovskite layers in terms of the perovskite grain growth control, defect reduction, stability enhancement, etc. Herein, we first review the recent progress on additives during the fabrication of large area perovskite films for large scale perovskite solar cells and modules. We then focus on a comprehensive and in-depth understanding of the roles of additives for perovskite grain growth control, defects reduction, and stability enhancement. Further advancement of the scalable fabrication of high-quality perovskite films and solar cells using additives to further develop large area, stable perovskite solar cells are discussed

Highly Efficient Perovskite Solar Cells Enabled by Multiple Ligand Passivation

In the past decade, the efficiency of perovskite solar cells quickly increased from 3.8% to 25.2%. The quality of perovskite films plays vital role in device performance. The films fabricated by solution-process are usually polycrystalline, with significantly higher defect density than that of single crystal. One kind of defect in the films is uncoordinated Pb2+, which is usually generated during thermal annealing process due to the volatile organic component. Another detrimental kind of defect is Pb-0, which is often observed during the film fabrication process or solar cell operation. Because the open circuit voltage has a close relation with the defect density, it is thus desirable to passivate these two kinds of defects. Here, a molecule with multiple ligands is introduced, which not only passivates the uncoordinated Pb2+ defects, but also suppresses the formation of Pb-0 defects. Meanwhile, such a treatment improves the energy level alignment between the valence band of perovskite and the highest occupied molecular orbital of spiro-OMeTAD. As a result, the performance of perovskite solar cells significantly increases from 19.0% to 21.4%

Incremental Construction of Generalized Voronoi Diagrams on Pointerless Quadtrees

In robotics, Generalized Voronoi Diagrams (GVDs) are widely used by mobile robots to represent the spatial topologies of their surrounding area. In this paper we consider the problem of constructing GVDs on discrete environments. Several algorithms that solve this problem exist in the literature, notably the Brushfire algorithm and its improved versions which possess local repair mechanism. However, when the area to be processed is very large or is of high resolution, the size of the metric matrices used by these algorithms to compute GVDs can be prohibitive. To address this issue, we propose an improvement on the current algorithms, using pointerless quadtrees in place of metric matrices to compute and maintain GVDs. Beyond the construction and reconstruction of a GVD, our algorithm further provides a method to approximate roadmaps in multiple granularities from the quadtree based GVD. Simulation tests in representative scenarios demonstrate that, compared with the current algorithms, our algorithm generally makes an order of magnitude improvement regarding memory cost when the area is larger than 210×210. We also demonstrate the usefulness of the approximated roadmaps for coarse-to-fine pathfinding tasks

Comparison between emerging adults and adults in terms of contamination fear, post-COVID-19 PTSD and psychiatric comorbidity

The present study compared Chinese emerging adults and adults regarding the association between contamination fear, posttraumatic stress disorder post-COVID-19 and psychiatric comorbidity after controlling for demographic and trauma exposure variables. 1089 Chinese civilians (M = 382; F = 707) with a mean age of 26 years (M = 26.36, SD = 8.58) were recruited from different provinces in China via an online survey posted on mainstream Chinese social networking platforms. They completed a demographic page with questions on trauma exposure, the Vancouver Obsessional Compulsive Inventory, the Posttraumatic Stress Disorder Checklist for DSM-5 and the General Health Questionnaire-28. Results showed that 12.7%, 68.7% and 18.6% met criteria for full, partial and no PTSD, respectively. Emerging adults reported significantly lower levels of symptoms of re-experiencing, avoidance, somatic problems, anxiety and fear of contamination than adults. In both emerging adults and adults, contamination fear was correlated with PTSD and psychiatric comorbidity. High educational attainment was significantly correlated with psychiatric comorbidity in emerging adults, but with PTSD in adults. Length of quarantine was correlated with psychiatric comorbidity only in adults. In conclusion, both emerging adults and adults developed varying levels of contamination fear, posttraumatic stress and general psychological symptoms following the outbreak of COVID-19. Emerging adults were more resilient than adults in coping with distress

Scalable Fabrication of Stable High Efficiency Perovskite Solar Cells and Modules Utilizing Room Temperature Sputtered SnO2 Electron Transport Layer

Stability and scalability have become the two main challenges for perovskite solar cells (PSCs) with the research focus in the field advancing toward commercialization. One of the prerequisites to solve these challenges is to develop a cost-effective, uniform, and high quality electron transport layer that is compatible with stable PSCs. Sputtering deposition is widely employed for large area deposition of high quality thin films in the industry. Here the composition, structure, and electronic properties of room temperature sputtered SnO2 are systematically studied. Ar and O-2 are used as the sputtering and reactive gas, respectively, and it is found that a highly oxidizing environment is essential for the formation of high quality SnO2 films. With the optimized structure, SnO2 films with high quality have been prepared. It is demonstrated that PSCs based on the sputtered SnO2 electron transport layer show an efficiency up to 20.2% (stabilized power output of 19.8%) and a T-80 operational lifetime of 625 h. Furthermore, the uniform and thin sputtered SnO2 film with high conductivity is promising for large area solar modules, which show efficiencies over 12% with an aperture area of 22.8 cm(2) fabricated on 5 x 5 cm(2) substrates (geometry fill factor = 91%), and a T-80 operational lifetime of 515 h