Impact of Area Scaling on the Performance and Stability of Spin-Coated Organic Solar Cells

Abstract

Organic solar cells (OSCs) suffer from severe upscaling losses that are predominantly governed by resistive limitations, which hinder efficient lateral charge transport and extraction when reaching the centimeter scale with the current fabrication techniques. In this work, we analyze the impact of the area scaling (from 0.09 up to 4 cm²) on the performance and stability of spin-coated OSCs using PM6:Y7 and PM6:L8-BO in bulk heterojunctions architectures. Small-area devices (0.09 cm²) exhibit PCEs of ~17%, fill factors (FF) around 70%, and low series resistances (~1.3 Ω cm²). When scaling up to 4 cm², the open-circuit voltage remains nearly constant, whereas short-circuit current density and fill factor decrease, resulting in PCEs of 10.7% and 11.1% for PM6:Y7 and PM6:L8-BO, respectively. Atomic force microscopy (AFM) and spatially resolved EQE measurements show that efficiency losses arise mainly from increased series resistance (up to ~10 Ω cm²) and minor morphological non-uniformities rather than intrinsic limitations of spin coating process. The stability was also investigated showing PCE losses mainly governed by Jsc and FF reductions. PM6:Y7-based devices consistently display superior stability compared to PM6:L8-BO, particularly at larger active areas. These results demonstrate that while efficiency losses upon upscaling are primarily dictated by resistive constraints, the stability of spin-coated OSCs is not compromised at the centimeter scale. Moreover, PM6:Y7-based devices exhibit enhanced stability with increasing area.