Understanding the Electronic Structures and Absorption Properties of Porphyrin Sensitizers YD2 and YD2-o-C8 for Dye-Sensitized Solar Cells

Abstract

The electronic structures and excitation properties of dye sensitizers determine the photon-to-current conversion efficiency of dye sensitized solar cells (DSSCs). In order to understand the different performance of porphyrin dye sensitizers YD2 and YD2-o-C8 in DSSC, their geometries and electronic structures have been studied using density functional theory (DFT), and the electronic absorption properties have been investigated via time-dependent DFT (TDDFT) with polarizable continuum model for solvent effects. The geometrical parameters indicate that YD2 and YD2-o-C8 have similar conjugate length and charge transfer (CT) distance. According to the experimental spectra, the HSE06 functional in TDDFT is the most suitable functional for describing the Q and B absorption bands of porphyrins. The transition configurations and molecular orbital analysis suggest that the diarylamino groups are major chromophores for effective CT excitations (ECTE), and therefore act as electron donor in photon-induced electron injection in DSSCs. The analysis of excited states properties and the free energy changes for electron injection support that the better performance of YD2-o-C8 in DSSCs result from the more excited states with ECTE character and the larger absolute value of free energy change for electron injection.

Molecular design of porphyrin dyes for dye sensitized solar cells: A quantitative structure property relationship study

“…Hence it can be concluded that, the broad absorption in the visible and NIR region with intense and red‐shifted Q bands having a significant molar absorption coefficient features these 8 molecules as promising sensitizers to harvest maximum solar energy. These sensitizers can be further asserted as promising candidates for DSC by dominance of one of the first order hyperpolarizability tensors ( β XXX ) component because the dominance of one tensor component would yield to unidirectional charge transfer transition from donor to acceptor group, evident in YD2‐O‐C8 dye . Evident from the Supporting Information Table S9 that the tensor ( β XXX ) for most of promising sensitizers is dominant and is located parallel to axis involving charge‐transfer process and as a consequence yields unidirectional charge transfer transition from donor to acceptor group effectively.…”

Interaction of LD14 and TiO2 in dye-sensitized solar-cells (DSSC): A density functional theory study

“…The photo-induced electron injection in DSSCs can be viewed as a charge transfer (CT) process [41,42,54]. Using the Marcus theory for electron transfer [55], the CT can be associated with the free energy change for electron injection (ΔG inject ) [56].…”

Methodologies in Spectral Tuning of DSSC Chromophores through Rational Design and Chemical-Structure Engineering

“…Yet, there is a lack of significant absorption in the spectral region between these two bands, i.e., the Q-bands and Soret bands. It has been reported that the porphyrin macrocycle forms superior organic dyes using a co-sensitization method (YD2-o-C8) [130] in DSSCs, in which a cobalt-based electrolyte is able to achieve a comparable photoelectric conversion efficiency of 11% PCE compared to the conventional ruthenium-based N719 dye [41]. As a result, metalloporphyrin compounds, such as molecularly engineered metalloporphyrin, a Zn-porphyrin-based dye (coded as SM315), have previously been reported with impressive properties for DSSCs applications [125].…”