Effects of additional pi-spacers on the photovoltaic properties of organic dyes for efficient dye-sensitized solar cells: a theoretical study

摘要

Novel organic dyes were designed (MAX114-1-MAX114-7) by adding different pi-spacer groups to the reference dye (MAX114) for high efficiency of dye-sensitized solar cells (DSSCs). Their geometries, electronic structures and optical properties and photovoltaic performance were theoretically investigated by density functional theory (DFT) and time-dependent DFT (TD-DFT) methods. Photovoltaic parameters influencing power conversion efficiency (PCE) were calculated and discussed for DSSC applications, such as light-harvesting efficiency (LHE), electron injection driving force ( increment G(inj)), dye regeneration driving force ( increment G(reg)), nonlinear optical properties (NLO) and reorganization energy. The optimized geometries of designed dyes have more coplanarity than the MAX114, which is beneficial for efficient intramolecular charge transfer and the suppression of dye aggregation. The energy gaps of the designed dyes have significantly decreased compared to MAX114, leading to red-shifted absorption spectra and improved light-harvesting ability. It was found that the studied dyes have good electron injection and dye regeneration performance due to a more negative value of increment G(inj) and a lower value of increment G(reg). The results show that the designed dyes have a higher mu(normal), higher LHE, higher NLO properties, lower increment G(reg), reasonable increment G(inj), and a better balance of lambda(h) and lambda(e), resulting in a higher V-OC and J(SC) than MAX114. This indicates that the designed dyes (MAX114-1-MAX114-7) could be used as sensitizers to improve the effectiveness of DSSC devices.