# DFT-Based Design and Characterization of Organic Chromophores Based on Symmetric Thio-Bridge Quinoxaline Push–Pull (STQ-PP) for Solar Cells

## TL;DR

This paper computationally designs and evaluates new organic chromophores for solar cells, focusing on their electronic and optical properties to improve photon harvesting.

## Contribution

The study introduces and characterizes symmetric thio-bridge quinoxaline push–pull chromophores using DFT and TD-DFT methods for photovoltaic applications.

## Key findings

- DTTQ-DPP-1 has an energy gap of 0.82–0.86 eV and absorption extended beyond 800 nm, favoring low-energy photon harvesting.
- DTTQ-DPP has a larger energy gap (2.70 eV) and UV-localized absorption, suggesting lower photovoltaic performance.
- DTTQ-DPP-1 shows structural stability and rigidity, supporting its viability for solar cell applications.

## Abstract

Organic solar cells require molecular materials with broad absorption and proper energy-level alignment to maximize photon harvesting and charge transport; in this context, this work focuses on the computational design and characterization of π-conjugated push–pull chromophores, providing an integrated evaluation of their electronic, thermodynamic, and optoelectronic properties for photovoltaic applications. The chromophores were optimized using DFT/ b3lyp/6-31g+(d,p) in Gaussian16, incorporating solvation effects through the CPCM model. Electronic, thermodynamic, and optical properties were investigated using DFT and TD-DFT/CAM-B3LYP/6-311+G(d,p), including the calculation of absorption and emission spectra, first hyperpolarizability, and two-photon absorption. The STQ-PP chromophores exhibit differentiated optoelectronic responses, with DTTQ-DPP-1 showing an energy gap of 0.82–0.86 eV, stabilized LUMO levels between −2.50 and −2.61 eV, high electronic polarizability, and optical absorption extended beyond 800 nm, favoring the harvesting of low-energy photons, whereas DTTQ-DPP displays a gap close to 2.70 eV and absorption predominantly localized in the UV region, associated with potentially inferior photovoltaic performance. Compared with commercial donor materials, DTTQ-DPP-1 exhibits a red-shifted absorption into the NIR and a smaller gap, indicating enhanced low-energy photon capture; its structural stability and increased rigidity further support its photovoltaic viability.