Efficient side-chain engineering of thieno-imidazole salt-based molecule to boost the optoelectronic attributes of organic solar cells: A DFT approach.

This study focused on modeling and density functional theory (DFT) analysis of reference (AI1) and designed structures (AI11-AI15), based on the thieno-imidazole core, in order to create profitable candidates for solar cells. All the optoelectronic properties of the molecular geometries were computed using DFT and time dependent-DFT approaches. The influence of terminal acceptors on the bandgaps, absorption, hole and electron mobilities, charge transfer capabilities, fill factor, dipole moment, etc. Of the recently designed structures (AI11-AI15), as well as reference (AI1), were evaluated. Optoelectronics and chemical parameters of newly architecture geometries were shown to be superior to the cited molecule. The FMOs and DOS graphs also demonstrated that the linked acceptors remarkably improved the dispersion of charge density in the geometries under study, particularly in AI11 and AI14. Calculated values of binding energy and chemical potential confirmed the thermal stability of the molecules. All the derived geometries surpassed the AI1 (Reference) molecule in terms of maximum absorbance ranging from 492 to 532 nm (in chlorobenzene solvent) and a narrower bandgap ranging from 1.76 to 1.99eV. AI15 had the lowest exciton dissociation energy of 0.22eV as well as lowest electrons and hole dissociation energies, while AI11 and AI14 showed highest VOC, fill factor, power conversion efficiency (PCE), IP and EA (owing to presence of strong electron pulling cyano (CN) moieties at their acceptor portions and extended conjugation) than all the examined molecules, implying that they could be used to build elite solar cells with enhanced photovoltaic attributes.

Impact of various heterocyclic π-linkers and their substitution position on the opto-electronic attributes of the A-π-D-π-A type IECIO-4F molecule: a comparative analysis.

To investigate the consequence of different substitution positions of various π-linkers on the photovoltaic properties of an organic solar cell molecule, we have introduced two series of six three-donor molecules, by the substitution of some effective π-linkers on the A-π-D-π-A type reference molecule IECIO-4F (taken as IOR). In series "a" the thienyl or furyl bridge is directly linked between the donor and acceptor moieties, while in series "b" the phenyl ring of the same bridge is working as the direct point of attachment. The frontier molecular orbitals, density of states, transition density matrix, molecular electrostatic potential surfaces, exciton binding energy, excitation energy, wavelength of maximum absorption, open-circuit voltage, fill factor, and some other photovoltaic attributes of the proposed molecules were analyzed through density functional theory (DFT) and its time-dependent (TD) approach; the TD-DFT method. Though both series of newly derived molecules were a step up from the reference molecule in almost all of the studied characteristics, the "a" series (IO1a to IO3a) seemed to be better due to their desirable properties such as the highest maximum absorption wavelength (λ max), open-circuit voltage, and fill factor, along with the lowest excitation and exciton dissociation energy, etc. of its molecules. Also, the studied morphology, optical characteristics, and electronic attributes of this series of proposed molecules signified the fact that the molecules with thienyl or furyl ring working as the direct link between the acceptor and donor molecules showed enhanced charge transfer abilities, and could provide a maximum quantum yield of the solar energy supplied.

DFT study of alkali and alkaline earth metal-doped benzocryptand with remarkable NLO properties.

Strategies for designing remarkable nonlinear optical materials using excess electron compounds are well recognized in literature to enhance the applications of these compounds in nonlinear optics. In this study, density functional theory simulations are performed to study alkali and alkaline earth metal-doped benzocryptand using the B3LYP/6-31G+(d, p) level of theory. Vertical ionization energies (VIEs), reactivity parameters, interaction energies, and binding energies exposed the thermodynamic stability of these complexes. FMO analysis revealed that HOMO is located on alkali metals having polarized electrons, which are easy to excite. The doping strategy enhanced the charge transfer with low bandgap energy in the range of 0.68-2.23 eV, which is lower than that of the surface BC (5.50 eV). Also, the lower transition energies and higher oscillator strength indicate that these complexes exhibit excellent electronic and optical properties. Non-covalent interaction analysis suggested the presence of van der Waals interactions between dopants and surface. IR analysis provided information about the frequencies of stretching vibrations present in the complexes due to different bonds. UV-vis analysis revealed that all the newly designed excess electron complexes are transparent in the UV region and possessed maximum absorption in the visible and NIR region, ranging from 753.6 to 2150 nm, which is higher than the surface (244 nm). Thus, these complexes have a potential for high-performance NLO materials in the applications of optics. Natural bond orbital analysis (NBO), transition density matrix (TDM), electron density difference map (EDDM), and density of state (DOS) analyses were also performed to study the charge transfer properties. Moreover, these complexes possessed remarkable optoelectronic properties due to a significant increase in the isotropic linear polarizability (α iso) in the range of 629.59-1423.23 au. Further, these systems demonstrated an extraordinary large total first hyperpolarizability (ß tl) in the range of 3695.55-910 706.43 au. The rationalization of hyperpolarizability by the two-level model reflected a noteworthy increase in ß tl because of low transition energies (ΔE) and high transition dipole moment (Δµ). Thus, our results showed that alkali and alkaline earth metal-doped BC might be a competitor for efficient nonlinear optical properties with practical applications in the area of optoelectronics.

Association of Acne with Face Mask in Healthcare Workers Amidst the COVID-19 Outbreak in Karachi, Pakistan.

BACKGROUND: In the wake of coronavirus (COVID-19) global alert, people have begun to practice safety measures in order to reduce the exposure to life-threatening disease. The largest at risk population is undoubtedly the frontline healthcare workers (HCWs) who are using personal protective equipment (PPE), essentially face masks, to battle against this deadly virus. This study was conducted with the prime intention to reveal an association between face mask and acne and measure the prevalence of acne amongst HCWs amidst COVID-19 outbreak in Karachi. Furthermore, this study aimed to identify the type of mask generating acne, locate the common sites, assess the severity and establish an association of mask use with the skin type. METHODS: This cross-sectional study was carried out at Medicare Cardiac and General Hospital, Jinnah Medical College Hospital, Jinnah Postgraduate Medical Centre and Jamal Noor Hospital located in Karachi, Pakistan. A total of 348 HCWs were interviewed, of which only 193 met the inclusion criteria. All information was recorded on a predesigned proforma and analyzed using SPSS 25.0. RESULTS: Among 193 participants, acne was prevalent in 103 (53.4%) participants with maximum cases reported in female HCWs, and in doctors (p<0.05). Out of 73 HCWs using N-95 masks, 46 (44.7%) developed acne, with a p-value of 0.036. Skin type and past history of acne also yielded statistically significant results. Among all the skin types, HCWs with oily skin (64, 62.1%) were prone to face resurgence of acne or new-onset acne. The most common sites of eruption of acne were along the cheeks (45.1%) followed by the nose (40.9%). Majority of the population suffered from mild acne. Moderate and severe acne eruption was particularly observed in those wearing N-95 and surgical masks. CONCLUSION: The use of face masks is associated with high rates of acne eruption. Disseminating the guidelines and indications of World Health Organization (WHO) regarding proper use of mask, encouraging awareness among HCWs and following proper doffing and donning protocol as endorsed by Centers for Disease Control and Prevention (CDC) will possibly minimize the adverse reactions.