Intermolecular CT excitons enable nanosecond excited-state lifetimes in NIR-absorbing non-fullerene acceptors for efficient organic solar cells

State-of-the-art Y6-type molecular acceptors exhibit nanosecond excited-state lifetimes despite their low optical gaps (~1.4 eV), thus allowing organic solar cells (OSCs) to achieve highly efficient charge generation with extended near-infrared (NIR) absorption range (up to ~1000 nm). However, the precise molecular-level mechanism that enables low-energy excited states in Y6-type acceptors to achieve nanosecond lifetimes has remained elusive. Here, we demonstrate that the distinct packing of Y6 molecules in film leads to a strong intermolecular charge-transfer (iCT) character of the lowest excited state in Y6 aggregates, which is absent in other low-gap acceptors such as ITIC. Due to strong electronic couplings between the adjacent Y6 molecules, the iCT-exciton energies are greatly reduced by up to ~0.25 eV with respect to excitons formed in separated molecules. Importantly, despite their low energies, the iCT excitons have reduced non-adiabatic electron-vibration couplings with the electronic ground state, thus suppressing non-radiative recombination and allowing Y6 to overcome the well-known energy gap law. Our results reveal the fundamental relationship between molecular packing and nanosecond excited-state lifetimes in NIR-absorbing Y6-type acceptors underlying the outstanding performance of Y6-based OSCs

Sodium-glucose Cotransporter 2 (SGLT2) Inhibitors vs. Dipeptidyl Peptidase-4 (DPP4) inhibitors for new-onset dementia: A propensity score-matched population-based study with competing risk analysis

The effects of sodium-glucose cotransporter 2 inhibitors (SGLT2I) and dipeptidyl peptidase-4 inhibitors (DPP4I) on new-onset cognitive dysfunction in type 2 diabetes mellitus remain unknown. This study aimed to evaluate the effects of the two novel antidiabetic agents on cognitive dysfunction by comparing the rates of dementia between SGLT2I and DPP4I users. This was a population-based cohort study of type 2 diabetes mellitus patients treated with SGLT2I and DPP4I between January 1, 2015 and December 31, 2019 in Hong Kong. Exclusion criteria were <1-month exposure or exposure to both medication classes, or prior diagnosis of dementia or major neurological/psychiatric diseases. Primary outcomes were new-onset dementia, Alzheimer's, and Parkinson's. Secondary outcomes were all-cause, cardiovascular, and cerebrovascular mortality. A total of 13,276 SGLT2I and 36,544 DPP4I users (total = 51,460; median age: 66.3 years old [interquartile range (IQR): 58-76], 55.65% men) were studied (follow-up: 472 [120-792] days). After 1:2 matching (SGLT2I: = 13,283; DPP4I: = 26,545), SGLT2I users had lower incidences of dementia (0.19 vs. 0.78%, < 0.0001), Alzheimer's (0.01 vs. 0.1%, = 0.0047), Parkinson's disease (0.02 vs. 0.14%, = 0.0006), all-cause (5.48 vs. 12.69%, < 0.0001), cerebrovascular (0.88 vs. 3.88%, < 0.0001), and cardiovascular mortality (0.49 vs. 3.75%, < 0.0001). Cox regression showed that SGLT2I use was associated with lower risks of dementia (hazard ratio [HR]: 0.41, 95% confidence interval [CI]: [0.27-0.61], < 0.0001), Parkinson's (HR:0.28, 95% CI: [0.09-0.91], = 0.0349), all-cause (HR:0.84, 95% CI: [0.77-0.91], < 0.0001), cardiovascular (HR:0.64, 95% CI: [0.49-0.85], = 0.0017), and cerebrovascular (HR:0.36, 95% CI: [0.3-0.43], < 0.0001) mortality. The use of SGLT2I is associated with lower risks of dementia, Parkinson's disease, and cerebrovascular mortality compared with DPP4I use after 1:2 ratio propensity score matching. [Abstract copyright: Copyright © 2021 Mui, Zhou, Lee, Leung, Lee, Chou, Tsang, Wai, Liu, Wong, Chang, Tse and Zhang.

Latent membrane protein 1 and macrophage-derived TNFα synergistically activate and mobilize invadopodia to drive invasion of nasopharyngeal carcinoma

Invadopodia are actin-rich membrane protrusions that digest the matrix barrier during cancer metastasis. Since the discovery of invadopodia, they have been visualized as localized and dot-like structures in different types of cancer cells on top of a 2D matrix. In this investigation of Epstein–Barr virus (EBV)-associated nasopharyngeal carcinoma (NPC), a highly invasive cancer frequently accompanied by neck lymph node and distal organ metastases, we revealed a new form of invadopodium with mobilizing features. Integration of live-cell imaging and molecular assays revealed the interaction of macrophage-released TNFα and EBV-encoded latent membrane protein 1 (LMP1) in co-activating the EGFR/Src/ERK/cortactin and Cdc42/N-WASP signaling axes for mobilizing the invadopodia with lateral movements. This phenomenon endows the invadopodia with massive degradative power, visualized as a shift of focal dot-like digestion patterns on a 2D gelatin to a dendrite-like digestion pattern. Notably, single stimulation of either LMP1 or TNFα could only enhance the number of ordinary dot-like invadopodia, suggesting that the EBV infection sensitizes the NPC cells to form mobilizing invadopodia when encountering a TNFα-rich tumor microenvironment. This study unveils the interplay of EBV and stromal components in driving the invasive potential of NPC via unleashing the propulsion of invadopodia in overcoming matrix hurdles.</p

Sodium-glucose cotransporter 2 (SGLT2) inhibitors vs. dipeptidyl peptidase-4 (DPP4) inhibitors for new-onset dementia: A propensity score-matched population-based study with competing risk analysis

Introduction: The effects of sodium-glucose cotransporter 2 inhibitors (SGLT2I) and dipeptidyl peptidase-4 inhibitors (DPP4I) on new-onset cognitive dysfunction in type 2 diabetes mellitus remain unknown. This study aimed to evaluate the effects of the two novel antidiabetic agents on cognitive dysfunction by comparing the rates of dementia between SGLT2I and DPP4I users. Methods: This was a population-based cohort study of type 2 diabetes mellitus patients treated with SGLT2I and DPP4I between January 1, 2015 and December 31, 2019 in Hong Kong. Exclusion criteria were <1-month exposure or exposure to both medication classes, or prior diagnosis of dementia or major neurological/psychiatric diseases. Primary outcomes were new-onset dementia, Alzheimer's, and Parkinson's. Secondary outcomes were all-cause, cardiovascular, and cerebrovascular mortality. Results: A total of 13,276 SGLT2I and 36,544 DPP4I users (total n = 51,460; median age: 66.3 years old [interquartile range (IQR): 58–76], 55.65% men) were studied (follow-up: 472 [120–792] days). After 1:2 matching (SGLT2I: n = 13,283; DPP4I: n = 26,545), SGLT2I users had lower incidences of dementia (0.19 vs. 0.78%, p < 0.0001), Alzheimer's (0.01 vs. 0.1%, p = 0.0047), Parkinson's disease (0.02 vs. 0.14%, p = 0.0006), all-cause (5.48 vs. 12.69%, p < 0.0001), cerebrovascular (0.88 vs. 3.88%, p < 0.0001), and cardiovascular mortality (0.49 vs. 3.75%, p < 0.0001). Cox regression showed that SGLT2I use was associated with lower risks of dementia (hazard ratio [HR]: 0.41, 95% confidence interval [CI]: [0.27–0.61], P < 0.0001), Parkinson's (HR:0.28, 95% CI: [0.09–0.91], P = 0.0349), all-cause (HR:0.84, 95% CI: [0.77–0.91], P < 0.0001), cardiovascular (HR:0.64, 95% CI: [0.49–0.85], P = 0.0017), and cerebrovascular (HR:0.36, 95% CI: [0.3–0.43], P < 0.0001) mortality. Conclusions: The use of SGLT2I is associated with lower risks of dementia, Parkinson's disease, and cerebrovascular mortality compared with DPP4I use after 1:2 ratio propensity score matching

Charge Carrier Transport and Injection Across Organic Heterojunctions

The discovery of highly efficient organic light-emitting diodes (OLEDs) in the 1980s has stimulated extensive research on organic semiconductors and devices. Underlying this breakthrough is the realization of the organic heterojunction (OH). Besides OLEDs, the implementation of the OH also significantly improves the power conversion efficiency in organic photovoltaic cells (OPVs). The continued technological advancements in organic electronic devices depend on the accumulation of knowledge of the intrinsic properties of organic materials and related interfaces. Among them, charge-carrier transport and carrier injection are two key factors that govern the performance of a device. This thesis mainly focuses on the charge carrier injection and transport at organic heterojunctions. The carrier transport properties of different organic materials used in this study are characterized by time-of-flight (TOF) and admittance spectroscopy (AS). An injection model is formulated by considering the carrier distribution at both sides of the interface. Using a steady-state simulation approach, the effect of accumulated charges on energy level alignment at OH is revealed. Instead of a constant injection barrier, it is found that the barrier varies with applied voltage. Moreover, an escape probability function in the injection model is modified by taking into account the total hopping rate and available hopping sites at the interface. The model predicts that the injection current at low temperature can be dramatically modified by an extremely small density of deep trap states. More importantly, the temperature dependence of the injection current is found to decrease with increasing barrier height. This suggests that extracting the barrier height from the J vs 1/T plot, as commonly employed in the literature, is problematic. These theoretical predictions are confirmed by a series of experiments on heterojunction devices with various barrier heights. In addition, the presence of deep trap states is also consistent with carrier mobility measurements at low temperature. From the point of view of application, an interface chemical doping method is proposed to engineer the carrier injection at an organic heterojunction. It is found that the the injection current can be effectively increased or suppressed by introducing a thin (2 nm) doped organic layer at the interface. This technique is further extended to study the impact of an injection barrier at the OH. in OLEDs, on device performance. It is shown that a 0.3 eV injection barrier at the OH, that is normally negligible at metal/organic interface, can reduce the device efficiency by 25 %. This is explained by the carrier distribution in the density-of-states at the OH. Furthermore, the carrier transport properties in a bulk heterojunction system are investigated. The bulk heterojunction consists of an interpenetrating network of a polymeric electron donor and a molecular electron acceptor. This material system has been studied in the last few years as an attractive power conversion efficiency (5% under AM 1.5) of OPV cells has been demonstrated. It is found that the electron mobility is greatly dependent on the thermal treatment of the film. Interfacial dipole effect at the heterojunction between the donor and the acceptor is proposed to be the determining factor that alters the carrier mobility in different nano-scale structures.Ph

Charge Carrier Transport and Injection Across Organic Heterojunctions

The discovery of highly efficient organic light-emitting diodes (OLEDs) in the 1980s has stimulated extensive research on organic semiconductors and devices. Underlying this breakthrough is the realization of the organic heterojunction (OH). Besides OLEDs, the implementation of the OH also significantly improves the power conversion efficiency in organic photovoltaic cells (OPVs). The continued technological advancements in organic electronic devices depend on the accumulation of knowledge of the intrinsic properties of organic materials and related interfaces. Among them, charge-carrier transport and carrier injection are two key factors that govern the performance of a device. This thesis mainly focuses on the charge carrier injection and transport at organic heterojunctions. The carrier transport properties of different organic materials used in this study are characterized by time-of-flight (TOF) and admittance spectroscopy (AS). An injection model is formulated by considering the carrier distribution at both sides of the interface. Using a steady-state simulation approach, the effect of accumulated charges on energy level alignment at OH is revealed. Instead of a constant injection barrier, it is found that the barrier varies with applied voltage. Moreover, an escape probability function in the injection model is modified by taking into account the total hopping rate and available hopping sites at the interface. The model predicts that the injection current at low temperature can be dramatically modified by an extremely small density of deep trap states. More importantly, the temperature dependence of the injection current is found to decrease with increasing barrier height. This suggests that extracting the barrier height from the J vs 1/T plot, as commonly employed in the literature, is problematic. These theoretical predictions are confirmed by a series of experiments on heterojunction devices with various barrier heights. In addition, the presence of deep trap states is also consistent with carrier mobility measurements at low temperature. From the point of view of application, an interface chemical doping method is proposed to engineer the carrier injection at an organic heterojunction. It is found that the the injection current can be effectively increased or suppressed by introducing a thin (2 nm) doped organic layer at the interface. This technique is further extended to study the impact of an injection barrier at the OH. in OLEDs, on device performance. It is shown that a 0.3 eV injection barrier at the OH, that is normally negligible at metal/organic interface, can reduce the device efficiency by 25 %. This is explained by the carrier distribution in the density-of-states at the OH. Furthermore, the carrier transport properties in a bulk heterojunction system are investigated. The bulk heterojunction consists of an interpenetrating network of a polymeric electron donor and a molecular electron acceptor. This material system has been studied in the last few years as an attractive power conversion efficiency (5% under AM 1.5) of OPV cells has been demonstrated. It is found that the electron mobility is greatly dependent on the thermal treatment of the film. Interfacial dipole effect at the heterojunction between the donor and the acceptor is proposed to be the determining factor that alters the carrier mobility in different nano-scale structures.Ph

An evaluation on the implementation of environmental protection policies in Hong Kong

published_or_final_versionPublic AdministrationMasterMaster of Public Administratio