Enhancing Adhesion and Reducing Charge Extraction Barrier Achieves 19.32% Efficiency in Inverted Organic Solar Cells with a Laminated Active Layer

Laminated film transfer has emerged as a promising technique for fabricating multilayer stacked structures in organic solar cells. However, challenges such as film transfer failure, loss of film integrity, and restricted charge transfer have limited its broader application. Herein, the focus is on optimizing the interfacial work of adhesion and energy levels to overcome these limitations, aiming to develop highly efficient inverted organic solar cells with laminated active layers. By selecting fullerene derivatives to modulate the work function and surface energy of the zinc oxide (ZnO) layer, film integrity and charge transfer with lamination are significantly enhanced. Specifically, when PC₆₁BM is cast on top of ZnO, it significantly improved the contact between the active layer of D18:L8-BO and the target substrate, leading to the successful and complete transfer of the organic film. Consequently, inverted devices are achieved with an optimal efficiency of 19.32%, attributed to the improved charge extraction, a significant reduction of trap states, and suppressed bimolecular recombination. The laminated devices outperform those fabricated using spin-coating, demonstrating the considerable potential for fabricating multilayer stacked thin-film optoelectronic devices, offering an alternative to traditional solution processing techniques, and paving the way for advanced printing in organic solar cells.