Theoretical study on the efficiency of new organic dyes based on (E)-2-(2-(thiophen-3-yl)vinyl)-1,1′-bipyrrole as dye-sensitized solar cell sensitizers

Dye-sensitized solar cells (DSSCs) have gained critical importance as a leading emerging photovoltaic technology for low-cost power generation due to their simple production, light weight, applicability to the development of flexible photovoltaic devices, and use of abundant and inexpensive materials, including advantageous metal-free organic dyes. In this context, as a continuation of our work on DSSCs, a theoretical examination using density functional theory (DFT) and time-dependent density functional theory (TD-DFT) was conducted to evaluate the photovoltaic performance of eight new organic dyes. Each dye contains an electron donor group ((E)-2-(2-(thiophen-3-yl)vinyl)-1,1′-bipyrrole), an electron acceptor group (cyanoacrylic acid (CCA)), and four auxiliary donor/acceptor groups, i.e., 3,4-ethylenedioxythiophene (EDOT), furan/benzothiadiazole (BTZ), diketopyrrolopyrrole (DPP) linked to π-conjugated bridges such as styrene or thiophene. We calculated several parameters for each dye, including E_HOMO, E_LUMO, E_gap, λ_max, E_ex, pen-circuit photovoltage (V_OC), light harvesting efficiency (LHE), regeneration driving force (ΔG_reg), electron injection driving force (ΔG_inject), and excitation lifetime (τ) to determine the photovoltaic efficiency of each dye. The results showed that the new dyes exhibited good performance and remarkable energy-conversion efficiencies. Additionally, all investigated dyes posed as promising candidates for the generation of effective DSSC sensitizers, particularly M₆, which contained a styrene-linked EDOT auxiliary donor group.