Transfer-Printed N-Type Conductive Polymer as Top Electrode for High-Efficiency Fully Solution-Processed Organic Solar Cells with Multifunctionality

Solution-printable processing represents a significant advantage for organic solar cells (OSCs), and the development of printable top electrodes is critical to achieve fully solution-processed organic photovoltaics. Currently, conventional solution-processed top electrodes often face challenges, such as damage to the underlying structure or poor interfacial contact. For the cathode, it is more appropriate to use n-type conducting materials with a low work function (WF). In this work, the combined n-type conductive polymer poly(3,7-dihydrobenzo[1,2-b:4,5-b']difuran-2,6-dione):poly(2-ethyl-2-oxazoline) (PBFDO:PEOx) is used as a top electrode in OSCs via transfer printing, enabling a robust, nondestructive contact between the printed top electrode and the interfacial layer. Due to its high conductivity, suitable WF, and protective role on the underlying structure, the introduced PBFDO:PEOx electrode promotes charge transfer and extraction while reducing nonradiative charge recombination and energy loss. As a result, OSCs based on PBFDO:PEOx/AgNWs printed top electrodes ultimately achieve a power conversion efficiency (PCE) of 14.2%, which is one of the highest PCE values among fully solution-processed OSCs without mirrors. Furthermore, the devices with PBFDO:PEOx electrodes exhibit an infrared blocking efficiency of over 80%, providing both excellent power generation and thermal insulation properties. This work presents a novel approach to the fabrication of printable top electrodes, providing a promising route for the advancement of fully solution-printed electronic devices.