Orientation dependent molecular electrostatics drives efficient charge generation in homojunction organic solar cells

Organic solar cells usually utilise a heterojunction between electron-donating (D) and electron-accepting (A) materials to split excitons into charges. However, the use of D-A blends intrinsically limits the photovoltage and introduces morphological instability. Here, we demonstrate that polycrystalline films of chemically identical molecules offer a promising alternative and show that photoexcitation of α-sexithiophene (α-6T) films results in efficient charge generation. This leads to α-6T based homojunction organic solar cells with an external quantum efficiency reaching up to 44% and an open-circuit voltage of 1.61 V. Morphological, photoemission, and modelling studies show that boundaries between α-6T crystalline domains with different orientations generate an electrostatic landscape with an interfacial energy offset of 0.4 eV, which promotes the formation of hybridised exciton/charge-transfer states at the interface, dissociating efficiently into free charges. Our findings open new avenues for organic solar cell design where material energetics are tuned through molecular electrostatic engineering and mesoscale structural control

Estimation of Vitamin D levels Among Female Students at University of Sciences and Technology, Aden, Yemen. A Cross-sectional Analysis

Background: Hypovitaminosis D is considered a major public health problem where it is estimated that more than one billion people are affected around the world. In Yemen, the vitamin D status among young females was not clear. Objective: This study aimed to state the level of vitamin D among female students at the University of Sciences and Technology and to determine the risk factors contributing to vitamin D status among those females. Method: An analytical cross-sectional study was conducted on 150 female students. Results: The total mean ± SD was 21.5 ± 2.7 years. The min-max of the total age was 18 years and 29 years. The overall prevalence of HVD among female students was 89.3% where 82.7% were insufficient and 6.7% were deficient. Symptoms such as muscle pain, bone pain, and hair loss of HVD were statistically associated with vitamin D status (p=0.001) in each. A statistically significant association was found among those who used sunscreen and did not take vitamin D supplements (p=0.001) in each. Conclusion: It can be concluded from this study that the prevalent rate of HVD among female college students in Aden, Yemen, was high and higher than most reported among females globally. The majority of female college students had VDI, while a few had VDD.  Using sunscreen and not taking vitamin D supplements increase the risk of HVD

Growth of organic crystal thin film by a new method: Rectangular heater heated pedestal growth method

In the present investigation, to make a phase matched crystal for any wavelength, we report the growth of thin film of 2-adamantylamino-5-nitropyridine (AANP) from molten state by a new and simple technique namely rectangular heater heated pedestal growth method. Using this method crystal thin film has been grown along a, b, c-directions and along the phase matching direction at 1.55 µm wavelength (60° from c-axis towards b-axis). Temperature profile of the growth cell has been studied to confirm its stability. X-ray diffraction studies confirmed the direction in which the film has been grown. Second harmonic light from 1.55 µm laser was clearly detected just in plane of the crystal grown towards the phase matched angle of the wavelength