SPONTANEOUS INTERLAYER FORMATION IN OSC WITH SILVER CONTACT FOR ENHANCED DEVICE PERFORMANCE

Understanding the organic/metal interface in organic solar cells (OSC) enabled significant enhancement to performance and ambient stability through incorporation of interlayers – ultrathin organic or inorganic layers positioned between the metal and organic active layer. Recently, suggested a simple interlayer processing methodology that is also compatible with roll-to-roll processing and printing manufacturing. In this approach, small amounts of the interlayer material are mixed as additives int eh active layer. The key step is additive migration towards the organic/metal interface driven by additive-metal interaction during electrode deposition. The migration of the interlayer-forming additives depends on the strength of this interaction versus other factors, such as the size of the additive, the properties of the matrix, interactions with the bottom substrate, additive surface-energy, etc. In this presentation, we will focus on silver contacts and P3HT:PCBM blends as a platform for investigating ambient-stable devices, and report the migration of judiciously selected additives, hexa(ethyleneglycol)-dithiol (HEG-DT) and 1,4-benzenedimethanethiol (BDMT), both thiol-terminated and known to form interlayers on Ag. Silver Step-deposition accompanied by in-situ photoelectron spectroscopy (XPS and UPS) reveals the selective migration of the additive to the organic/silver interface and energy level adjustment of the interfacial electrochemical potential. In OSC, adjusting the energy level alignment properly increases the short circuit current (Jsc), open circuit voltage (Voc) and fill factor (FF). Finally, we will show that the generated interlayer also significantly improves the ambient stability of unencapsulated OPV devices.