Tailoring photovoltaic and mechanical properties of organic solar cells using self-assembled monolayers

Self-assembled monolayers (SAMs) have emerged as promising hole transport layers (HTLs) in organic solar cells (OSCs). The compound 2PACz has demonstrated superior performance compared to the conventional PEDOT: PSS. The latter is known to have poor stability and can also suffer from weak interfacial adhesion energies, leading to delamination failures within the device stack. Our investigation is focused on the impact of SAMS on OSC performance, operational stability, and mechanical stability. We hypothesize that halogenation of 2PACz will enhance adhesion strength through electrostatic bonding. We have conducted a comparative analysis of a number of SAMs including Cl-2PACz, Br-2PACz, and MeO-2PACz. We explore their impact on adhesion through peel tests and DCB tests. We show that the use of 2PACz results in a threefold increase in peeling strength relative to PEDOT: PSS. Additionally, our OSCs exhibited nearly a 1% increase in PCE with Br-2PACz.