Enhancing physicochemical durability and photoelectronic performance beyond bendable large-area organic photoelectronic devices through tailored multilayer interface

• Development of novel bilayer ETL for organic photo-electric conversion devices. • Enhanced device performance of flexible organic solar cells and photodetectors. • Large-area flexible organic solar cell modules with enhanced PCE of 12.63 %. • Development of efficient OPDs high responsivity and excellent specific detectivity. Photoelectronic devices, such as organic solar cells (OSCs) and organic photodetector (OPDs), play a crucial role in the development of renewable energy technologies, with an emphasis on achieving high efficiency, photoresponse and mechanical stability. This study presents a novel, annealing-free bilayer electron transport layer (ETL) comprising polyethyleneimine ethoxylated zinc oxide nanoparticles (PE-ZnO) and protonated polyethyleneimine (p-PEIE) for inverted flexible organic photoelectronic conversion devices, with significantly improves overall efficiency and mechanical durability. This novel ETL configuration demonstrated a not only increased the power conversion efficiency (PCE) of flexible OSC devices up to 15.50 %, but also demonstrated outstanding mechanical stability. In addition to bending-flexural stress, where the devices retained 96.95 % efficiency at 0.75 cm radius, sliding-shear stress were also conducted to simulate rollable device conditions. Remarkably, the bilayer ETL maintained approximately 97 % of its initial efficiency after 5000 sliding cycles. Additionally, the large-area flexible OSCs with an active area of 54 cm 2 , reached PCE of 12.63 %, proving to be 81.5 % as efficient as small-area flexible cells, demonstrating scalability and practical viability. The application of bilayer ETL in flexible OPDs also results in significant reduction in dark current, enhanced photoresponse, and excellent mechanical stability indicating a robust solution for both solar energy harvesting and light sensing technologies. These findings provide a universal solution for improving the physicochemical durability and photoelectronic performance of bendable large-area organic photoelectronic devices.