Calibrated Optoelectronic TCAD Optimization of All-Organic and Hybrid Organic/Crystalline Silicon Two-Terminal Tandem Solar Cells

Abstract

The increasing demand for high-efficiency photovoltaic technologies has intensified research into tandem solar cells (TSCs) as a promising strategy to surpass the performance limits of single-junction devices. In this study, a comprehensive optoelectronic simulation using a Silvaco ATLAS TCAD simulator is employed to design, optimize, and compare two tandem architectures: all-organic and hybrid organic/silicon TSCs. The all-organic configuration consists of polymer donors comprising a PBDB-T:F-M top sub-cell stacked with a PTB7-Th:COi8DFIC:PC71BM bottom sub-cell, while the hybrid configuration integrates a PBDB-T:F-M organic top cell with a crystalline Si bottom cell. Calibrated device models, validated against experimental data of the individual sub-cells, are used to evaluate tandem performance and guide systematic optimization. The two tandem architectures employ the same PBDB-T:F-M wide-bandgap organic top absorber (Eg~1.60 eV), while the rear sub-cell consists of either the PTB7-Th:COi8DFIC:PC71BM organic absorber (Eg~1.20 eV) or crystalline silicon (Eg~1.12 eV). The initial organic/organic tandem device accomplishes a power conversion efficiency (PCE) of 15.70% and JSC of 10.96 mA/cm2, whereas the organic/silicon tandem structure exhibits a higher initial PCE of 16.85% and JSC of 12.26 mA/cm2. Following absorber-thickness optimization, the all-organic and hybrid OSC/Si tandems achieve PCEs of 19.44% and 21.13%, respectively. Rather than constituting a simple efficiency ranking, the comparison reveals distinct optical, electrical, and technological trade-offs. The hybrid architecture benefits from the broader spectral utilization and efficient carrier collection of thin crystalline Si, whereas the all-organic configuration offers advantages associated with low-temperature solution processing, reduced material consumption, and potentially fully solution-processed photovoltaic fabrication. The calibrated comparative framework therefore provides design guidance for selecting and optimizing TSCs according to both performance and application requirements.