With the depletion of fossil energy resources and their associated environmental challenges, vigorous development of the solar energy industry holds significant importance in alleviating the strain on fossil fuel utilization, achieving the “dual carbon” goals, and constructing novel power systems. Solar cells, which harness the photovoltaic effect to directly convert solar energy into electricity, represent a critical technology in this endeavor. Among these, solid-state dye-sensitized solar cells (ss-DSSCs) stand out as an attractive third-generation photovoltaic technology. They overcome the risks of volatility and leakage inherent in traditional liquid electrolytes, offering enhanced stability, lower production costs, simplified encapsulation processes, superior temperature adaptability, minimal visible light absorption, and compatibility with 3D printing technologies. The selection of dye layer materials profoundly influences device performance. This study focuses on organic dyes as the research subject, which exhibit distinct advantages over conventional metal-based dyes, including simplified synthesis processes, reduced costs, and environmental friendliness. By establishing a computational model for organic dyes to investigate performance variations and optimize device architectures, this work aims to provide theoretical insights and methodological guidance for experimental research in advancing high-efficiency, eco-friendly ss-DSSCs.

Based on the SCAPS-1D software platform, an initial computational model, namely FTO/TiO₂/S5/Spiro-OMeTAD/Ag, was established and validated through fitting with experimental data to ensure accuracy. Subsequently, systematic investigations were conducted to evaluate the effects of multiple parameters on the four key performance parameters (i.e., open-circuit voltage V_oc, short-circuit current density J_sc, fill factor FF, and photoelectric conversion efficiency PCE) and current density-voltage (J-V) characteristics. Multiple parameters include the thickness and defect density of the dye layer, doping type and concentration in the charging transport layers, back-contact work function, and operating temperature. Through comprehensive parametric optimization, the optimal values and device architecture were determined. By analyzing the performance variation trends under different parameters, the underlying mechanisms were elucidated through the following aspects: band alignment relationships, carrier recombination and transport dynamics, bulk and interfacial defects, and heterojunction contact types. This comprehensive analysis provides insights into the fundamental factors affecting device performance, offering a mechanistic framework for optimizing the design and operation of solid-state dye-sensitized solar cells.

The dye S5 selected in this study exhibits a large absorption coefficient. As the thickness of the dye layer increases, the J_sc shows an upward trend, and the PCE reaches its maximum value at a thickness of 1 μm (Fig. 7). However, due to the increased probability of recombination, higher defect density, and elevated internal resistance, the FF and the V_oc are lower compared to their initial values. The acceptor doping density in the hole transports layer (HTL) has a more significant impact on device performance than the donor doping density in electron transports layer (ETL), primarily due to the energy level alignment between the layers. Increasing the HTL doping concentration significantly improves V_oc, with optimal performance achieved at a doping concentration of 1×10¹⁷ cm^-3 (Fig. 8). Conversely, excessive doping in the ETL introduces new defect states, leading to a decline in device performance. The optimal ETL doping concentration is 1×10¹⁸ cm^-3 (Fig. 9). The increase in defect density adversely affects all performance metrics. Considering the limitations of fabrication processes, the optimal defect density is determined to be 1×10¹³ cm^-3 (Fig. 10). For the back-contact metal, identifying a cost-effective alternative to precious metals is crucial for reducing device costs. Studies reveal that as the work function of the metal approaches 5 eV, the device performance initially improves and then gradually saturates (Fig. 11). Therefore, nickel (Ni) with a work function of 5.15 eV can be considered as promising candidate material. Temperature rise enhances J_sc but negatively impacts PCE and V_oc (Fig. 13). Additionally, elevated temperatures accelerate device aging and shorten operational lifetime.

In this simulation study, we employed a novel organic dye, S5, as the research subject and established an FTO/TiO?/S5/Spiro-OMeTAD/Ag model (Fig. 4) using the SCAPS-1D software, which was subsequently validated by fitting with experimental data. We systematically investigated the effects of defect density and thickness of the dye layer, doping concentrations of HTL and ETL, and the work function of the back-contact metal on the four key performance parameters of the device. The underlying mechanisms were analyzed, and the optimal parameter values for maximizing device performance were identified, realizing the optimization of the initial model into an optimal configuration. The optimized device achieved the PCE of 15.72%, the V_oc of 1.167 V, the J_sc of 17.99 mA/cm2, and the FFof 74.87%. Moreover, the absorption coefficient exhibited a significant enhancement within the wavelength range of 400?670 nm (Fig. 14). Furthermore, it is important to note that organic dyes exhibit a wide variety of types, with significant differences in key parameters such as bandgap, electron affinity, absorption coefficient, spectral absorption range, and HOMO and LUMO energy levels. However, when investigating the influence of material parameters on cell performance and optimizing device structure accordingly, the research approach and methodology adopted in this study possess universal reference value. This work highlights the immense potential of organic dyes in DSSC applications, providing a theoretical foundation and optimization framework for the further development and application of organic dyes, as well as offering valuable insights for future research on novel dye materials.