MOCA as a dual-function organic semiconductor: Theoretical insights into photoresponsive bandgap engineering and nonlinear optics

This research presents the first theoretical investigation of ۵-methyl-۲-oxo-۱,۳-oxazolidine-۴-carboxylic acid (MOCA) using Density Functional Theory (DFT) at the B۳LYP/۶-۳۱۱G(d,p) level. The primary objective is to explore MOCA’s structural, electronic, and nonlinear optical (NLO) properties, with emphasis on its response to UV illumination. Geometry optimization reveals a stable molecular framework, while Frontier Molecular Orbital (FMO) analysis demonstrates a significant reduction in the HOMO-LUMO energy gap upon UV exposure—from ۴.۶۶ eV in the ground state to ۲.۰۹–۲.۲۲ eV in the excited triplet state—indicating enhanced charge transport characteristics suitable for use as a window layer in photovoltaic devices. Furthermore, computed polarizability and first-order hyperpolarizability (βtot) values show strong NLO activity; βtot decreases from ۴.۴۱ × ۱۰⁻³⁰ esu before UV to ۳.۶۶ × ۱۰⁻³⁰ esu after irradiation, yet remains substantially higher than urea (۰.۳۷۲۸ × ۱۰⁻³⁰ esu), highlighting MOCA’s potential for applications in frequency doubling, optical switching, and electro-optic modulation. The observed photoresponsiveness suggests avenues for developing smart, tunable photonic materials. This work provides foundational computational data for MOCA, filling a critical gap in the literature and paving the way for future experimental validation.

کلیدواژه ها:

MOCA ، Density functional theory ، Electronic structure ، Optical properties ، Energy gap