Exploration of Photophysical and Nonlinear Properties of Salicylaldehyde-Based Functionalized Materials: A Facile Synthetic and DFT Approach

In Silico Designing of Thieno[2,3-b]thiophene Core-Based Highly Conjugated, Fused-Ring, Near-Infrared Sensitive Non-fullerene Acceptors for Organic Solar Cells

The performance of organic solar cells (OSCs) has been improving steadily over the last few years, owing to the optimization of device fabrication, fine-tuning of morphology, and thin-film processing. Thiophene core containing fused ring-type non-fullerene acceptors (NFAs) achieved significant proficiency for highly efficient OSCs. Quantum chemical computations are utilized herein with the motive of suggesting new NIR sensitive, highly efficient low-band gap materials for OSCs. A series of extended conjugated A-π-D-π-A architectured novel fused-ring NFAs (FUIC-1-FUIC-6) containing thieno[2,3-b]thiophene-based donor core are proposed by substituting the end-capped units of synthesized molecule F10IC. Different properties including frontier molecular orbital analysis, density of states analysis, transition density matrix analysis, excitation energy, reorganizational energies of both holes (λ_h) and electrons (λ_e), and open-circuit voltage (V _oc) were performed employing the density functional theory approach. Charge transfer analysis of the best-designed molecule with the donor complex was analyzed to comprehend the efficiency of novel constructed molecules (FUIC-1-FUIC-6) and compared with the reference. End-caped acceptor alteration induces the reduction of the energy gap between HOMO-LUMO (1.88 eV), tunes the energy levels, longer absorption in the visible and near-infrared regions, larger V _oc, smaller reorganizational energies, and binding energy values in designed structures (FUIC-1-FUIC-6) in comparison to reference (FUIC). The designed molecules show the best agreement with the PTBT-T donor polymer blend and cause the highest charge from the HOMO to the LUMO orbital. Our findings predicted that thieno[2,3-b] thiophene-based newly designed molecules would be efficient NFAs with outstanding photovoltaic characteristics and can be used in future applications of OSCs.

First theoretical probe for efficient enhancement of optical nonlinearity via structural modifications into phenylene based D-π-A configured molecules

The design of nonlinear optical (NLO) materials using conjugated molecules via different techniques is reported in the literature to boost the use of these systems in NLO. Therefore, in the current study, designed phenylene based non-fullerene organic compounds with a D-π-A framework were selected for NLO investigation. The initial compound (PMD-1) was taken as a reference and its seven derivatives (PMDC2-PMDC8) were made by introducing different acceptor moieties into the chemical structure of PMD-1. To explain the NLO findings, frontier molecular orbital (FMO), transition density matrix (TDM), density of states (DOS), natural bond orbital (NBO) and UV-Vis study of the title compounds was executed by applying the PBE1PBE functional with the 6-311G(d,p) basis set. The descending order of band gaps (E gap) was reported as PMDC7 (2.656) > PMDC8 (2.485) > PMD-1 (2.131) > PMDC3 (2.103) > PMDC2 (2.079) > PMDC4 (2.065) > PMDC5 (2.059) > PMDC6 (2.004), in eV. Global reactivity parameters (GRPs) were associated with E gap values as PMDC6 with the lowest band gap showed less hardness (0.0368 E h) and high softness (13.5785 E h). The UV-Vis investigation revealed that the maximum λ max (739.542 nm) was exhibited by PMDC6 in dichloromethane (DCM) as compared to other derivatives. Additionally, natural bond orbital (NBO) based findings revealed that PMDC6 exhibited the highest stability value (34.98 kcal mol-1) because of prolonged hyper-conjugation. The dipole moment (μ), average linear polarizability 〈α〉, first hyperpolarizability (β tot) and second hyperpolarizability (γ tot) were evaluated for the reference and its derivatives. Consequently, among the designed compounds, the highest β tot (4.469 × 10-27 esu) and γ tot (5.600 × 10-32 esu) values were shown by PMDC6. Hence, it's concluded from said results that these structural modifications proved PMDC6 as the best second and third order NLO candidate for various applications like fiber optics, signal processing and data storage.