Efficient roll-to-roll intense pulsed light treatment of ZnO layer for scalable flexible organic photovoltaics

In a roll-to-roll (R2R) printing process, a high-quality coating of nanoparticle-based materials is essential to preserving the efficiency and stability of solar cells throughout the coating length. This study proposes an efficient R2R-compatible post-treatment method employing intense pulsed light (IPL) to anneal a zinc oxide (ZnO) layer in organic solar cells (OSCs) and organic photovoltaic modules (OPMs). This approach stabilizes the chemical structure and optimizes the ZnO film morphology via rapid IPL annealing to remove residual solvent and promote complete oxidation. The optimal IPL treatment condition—an energy density of 0.15 J cm⁻²—results in a smooth and fully oxidized ZnO film. Flexible OSCs with different coating widths of 2 and 4 cm achieve power conversion efficiencies (PCEs) of 14.24% and 13.33%, respectively, following IPL treatment. Similarly, IPL-treated flexible OPMs demonstrate a PCE of 9.27%. Compared with devices incorporating pristine ZnO layers, the IPL-treated devices exhibit enhanced efficiency and long-term stability across all sizes. These results underscore the practical viability of IPL treatment for scalable fabrication of flexible OSCs and OPMs immediately following ZnO coating. Furthermore, as coating and annealing processes are expected to be integrated within an R2R system, IPL has emerged as a promising alternative to conventional thermal annealing, effectively mitigating substrate heat damage.