Shedding light on the optical and nonlinear optical properties of superalkali-doped borophene

Systematic Computational Designing of Efficient Phenalene and Pyrene Based Derivatives to Tune the Optical and Nonlinear Optical Response

Nonlinear optical (NLO) materials are among the smartest materials of the present era and are employed to modulate the phase and frequency of the laser. The present study presents a quantum chemical framework for tailoring nitrogen/boron-doped (N/B) derivatives of phenalene and pyrene through the terminal and central core modifications to check their NLO properties. The derivatives of these compounds have been designed by introducing various π-conjugated connectors and N/B heteroatoms in the phenalene and pyrene rings. Density functional theory (DFT) methods are used to optimize the ground state molecular geometries of designed compounds, represented as Phe-1 to Phe-4 (phenalene derivatives) and Pyr-1 to Pyr-4 (pyrene derivatives) at the M06-2X/6-311G* level of theory. A systematic impact of structural modulations is established by comparing first linear polarizability (α) and second hyperpolarizability (γ). For linear polarizability, Phe-4 has shown the highest value for αiso and αaniso values, which are 114.7 × 10-24 esu and 197.9 × 10-24 esu, respectively. For the second hyperpolarizability (γ), among the designed compounds, Pyr-4 has achieved the highest γ amplitude of 1929.9 × 10-36 esu owing to its unique molecular structural design and the presence of strong donor-acceptor groups. The origin of higher γ amplitudes is attributed to its lower energy electronic transition and higher oscillator strength. Further analysis of electronic parameters, such as electron density difference (EDD) maps, the density of states (DOS), electrostatic potentials, transition density matrix (TDM) analysis, and frontier molecular orbitals (FMOs) analysis, demonstrated the more effective intramolecular charge transfer (ICT), resulting in a good NLO response. The compounds were also analyzed for their potential in photovoltaic applications based on open circuit voltage values between 2.144 eV to 0.395 eV and light harvesting efficiency ranging from 0.486 eV to 0.989 eV. These findings suggest that the designed compounds can be suitable NLO materials and possess significant potential for photovoltaic applications.

Quantum chemical investigation of Z-shaped heptazethrenes derivatives with detailed structural parameters and singlet fission for photovoltaic applications

A variety of organic solar cells has been discovered, but there is a need for efficient optoelectronic material to obtain high power conversion efficiency. In this study, we derived new molecules from Z-shaped heptazethrene. We measured its photovoltaic parameters, including frontier molecular orbitals (where the energy gap decreases to 16% as compared to the reference), molecular electrostatic potential maps (more nucleophilic core), the density of states (partial and total), absorbance in Vis-IR region (in the range of 650-1000 nm), transition density matrix, and hole-electron mobility in terms of reorganization energy that showed 11% higher electron mobility (λ_e) and 52% higher hole mobility (λ_h) as compared to the reference. A comparable power conversion efficiency (∼9%) is obtained from a single photon. Using the concept of singlet fission, we can increase the efficiency twice using a single photon (based on the diradical character of the molecule). The diradical character of the entitled molecules was also calculated. The designed molecules fulfil the criteria of singlet fission that generate two excited triplets from a single photon (E_S1>2E_T1). The designed molecules are more stable than the reference indicated by the singlet-triplet energy gap, which is 37% higher. Hence this work assists the researcher in enhancing the efficiency of the solar cell.