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Imaging Dye Aggregation in MK-2, N3, N749, and SQ-2 dye?·?·?·TiO <sub/>2</sub> Interfaces That Represent Dye-Sensitized Solar Cell Working Electrodes
摘要： Dye-sensitized solar cells (DSSCs) are a strong contender for next-generation photovoltaic technology with niche applications as solar-powered windows. The performance of a DSSC is particularly susceptible to the dye sensitizer, which is adsorbed onto the surface of a wide-band-gap semiconductor such as TiO2, to form the working electrode. The nature by which such surfaces are sensitized stands to influence the resulting dye···TiO2 interfacial structure and thence the operational performance of the DSSC working electrode. In particular, a nanoscopic understanding of the sensitization process would ultimately help to improve DSSC device function. In this study, atomic force microscopy (AFM) is used to image the nanoscopic formation of dye···TiO2 interfacial structures. This employs, as case studies, four well-known DSSC dyes adsorbed onto amorphous TiO2 substrates: two ruthenium-based dyes, N3 and the Black Dye (N749); and two organic dyes, the thiophenylcarbazole, MK-2, and the zwitterionic squaraine, SQ-2. We discover that all four dyes present some form of aggregation upon sensitization of TiO2, whose spatial distributions show distinct nanoaggregate particle characteristics. These particle clusters of N749, N3, and MK-2 are found to assemble in lines of nanoaggregates, while clusters of SQ-2 dye chromophores distribute themselves randomly on the amorphous TiO2 substrates. This nanoparticle structural assembly persists even when these dye···TiO2 interfaces are fabricated using hundred-fold diluted dye sensitization concentrations. The formation of dye aggregates in N749 is further studied as a function of dye sensitization time. This tracks the pattern formation of aggregates of N749 and reveals that dye aggregation begins within the first hour and has completed within a 5 h period. The large expanse of dye nanoaggregates observed shows that dye···dye interactions are much more important than previously envisaged, while the nature of their spatial distribution can be related to different aggregation modes of the dye molecules. These nanostructural features will undoubtedly impact the performance of DSSCs.
关键词： aggregation,N749,dye-sensitized solar cell,atomic force microscopy,N3,SQ-2,MK-2
更新于2025-09-23 15:21:01
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Performance enhancement of dye-sensitized solar cells via co-sensitization of ruthenium (II) based N749 dye and organic sensitizer RK1
摘要： The aim of the reported study is to enhance the photovoltaic performance of a dye-sensitized solar cells (DSSCs) using co-sensitization approach and investigate how the concentration of an organic co-sensitizer influence the overall efficiency of the fabricated DSSCs. The overall efficiency of the fabricated DSSC with co-sensitization approach using a ruthenium (II) based dye, N749, and an organic sensitizer, RK1, is 8.15%. The solar cells were evaluated using UV–Vis spectroscopy, electrochemical impedance spectroscopy (EIS), incident photon to electron conversion efficiency (IPCE), and current-voltage (I-V) characteristics. The concentration of the organic co-sensitizer has a strong effect on the performance of the DSSC. An optimized solar cell fabricated with a dye solution of 0.2 mM RK1 and 0.3 mM N749 yielded a Jsc (mA/cm2) = 19.45, Voc (mV) = 688, FF (%) = 61 and power conversion efficiency (PCE) of η (%) = 8.15 under standard (AM1.5 G) 1 sun illumination (100 mW/cm2). The efficiency of co-sensitized DSSCs is far better than the efficiency of fabricated solar cells sensitized with individual dyes [N749 (η = 4.94%) and RK1 (η = 5.76%)]. The efficiency enhancement is due to the lower rate of recombination of electrons and holes, decreased I?/I3? competitive absorption, and lower aggregation of the dyes resulting from the synergistic action in the co-sensitized photovoltaic cells.
关键词： Co-sensitization,Efficiency,Ruthenium (II) based dye (N749),Photovoltaic,Organic Sensitizer (RK1),DSSC
更新于2025-09-23 15:19:57