Identifying the Optimal Thickness Range of IT-2Cl, Y6, and BTR-Cl for Ternary Layer-by-Layer Organic Solar Cells

Recently, researchers have been interested in ternary organic solar cells (OSCs), which improve light absorption, charge separation, and transport efficiency. Small molecule donors such as BTR-Cl and acceptors such as IT-2Cl and Y6 are recognized for their exceptional optical characteristics and well-matched energy levels, making them suitable for ternary OSC. This study aims to identify the optimal thickness range of IT-2Cl, Y6, and BTR-Cl for a ternary layer-by-layer (LbL) OSC configuration by integrating theoretical analysis, optical modeling, and electron generation rate simulations. Transmittance, absorbance, and reflectance (TAR) calculations were used to determine three distinct thickness regions, and representative thicknesses were chosen from each material region for generate rate characterization. Optical transfer matrix-based generate rate simulations using OghmaNano software provided depth-dependent electron generation data, which were analyzed for key characteristics such as maximum and average generation rates, total generation rate, and the first derivative of generate rate trends. The results identified the optimal thickness ranges as 28.4–90.2 nm for IT-2Cl, 33.4–106.2 nm for Y6, and 26.2–83.4 nm for BTR-Cl, balancing photon absorption efficiency and electron generation uniformity by correlating TAR parameters and generating rate characteristics. The findings of this work contribute to identifying optimal thickness ranges for IT-2Cl, Y6, and BTR-Cl based on their respective roles in the active layer of ternary LbL OSC, which can reduce their complexity in optimization.