Efficiency enhancement of black dye-sensitized solar cell by newly synthesized D-$\pi$-A coadsorbents: A theoretical study

TL;DR

This theoretical study uses DFT and TDDFT to analyze two coadsorbents, Y1 and Y2, revealing how their electronic and optical properties influence black dye-sensitized solar cell efficiency, especially through charge transfer and recombination effects.

Contribution

It provides a detailed theoretical comparison of Y1 and Y2 coadsorbents, explaining their different efficiencies and guiding future design of high-performance solar cell materials.

Findings

Y1 reduces recombination by decreasing I₂ near TiO₂ surface

Y1 exhibits higher J_sc and V_oc, leading to better efficiency

Solvatochromic shifts correlate with dipole moment changes during excitation

Abstract

In this work, using the DFT and TDDFT, we have theoretically studied the electronic and optical properties of the two recently synthesized coadsorbents Y1 and Y2, which were aimed to enhance the efficiency of the black dye-sensitized solar cells. To determine the solvatochromic shifts, both the implicit and mixed implicit-explicit models have been used. The connection between the solvatochromic shifts and the changes of dipole moments in the excitation process is discussed. The difference in excitation charge transfer is utilized to explain the experimentally observed difference in $J_{sc}$ for Y1 and Y2. Investigating the interactions of I$_2$ molecules in the electrolyte solution with the coadsorbents showed that with Y1 the recombination loss was weakened through decreasing the I$_2$ concentration near the TiO$_2$ surface, whereas with Y2 it was increased. As a result, the higher values of both $J_{sc}$ and $V_{oc}$ with Y1 coadsorbent explains its experimentally observed higher efficiency. The present study sheds light on how to design and engineer newer coadsorbents or organic dyes for higher efficiencies.