This paper introduces a novel tandem configuration, utilizing an all-thin film all-polymer solar cell
(all-PSC) with a wide bandgap of 1.76 eV for the front cell and Sb2Se3 with a narrow bandgap of 1.2 eV
for the bottom cell. The design of this tandem is performed by comprehensive optoelectronic TCAD
tools, essential for optimizing parameters across multiple layers to reach maximum power conversion
efficiency (PCE). Experimental validation of models is conducted through calibration and validation
against fabricated reference all-polymer and Sb2Se3 solar cells, yielding calibrated PCEs of
approximately 10.1% and 10.5%, respectively. Subsequently, validated simulation models for both
top and rear cells are utilized to design a 2-T all-polymer/Sb2Se3 tandem cell, which initially achieves a
PCE of 10.91%. Through systematic optimization steps, including interface engineering and
homojunction structure design, a remarkable PCE of 24.24% is achieved at the current matching
point, showcasing the potential of our proposed tandem solar cell design. This study represents a
significant advancement in the field of thin-film tandem solar cells, offering promising avenues for
efficient and cost-effective photovoltaic technologies, particularly in applications requiring flexibility.