PPACz is a self-assembled monolayer material featuring a dimethoxy-carbazole electron-rich terminal, a phenylethyl linker, and a phosphonic anchor. Carbazole-based self-assembled monolayer materials are known to show higher dipole moments and covalent binding capabilities, suppressing charge recombination and enhancing device stability. The phenylethyl linker extends the conjugation of the carbazole terminal, enabling heightened UV absorption capabilities and inherent UV resistance.
With a higher dipole moment of 2.60 D, PPACz demonstrates superior hole extraction ability while serving as a hole selection layer for high-performance perovskite solar cell devices. A power conversion efficiency of 26.1% is attained for p-i-n perovskite device based on PPACz as the hole transport layer. Over 90% of their initial efficiency after 540 h is retained for the unencapsulated device owing to the stronger anchoring of PPACz to the ITO substrate with improved interfacial stability.
Serving as hole selective contact for organic solar cells and perovskite solar cells, PPACzA is an alternative to PEDOT:PSS with superior performance and the convenience of solution deposition at low concentration, i.e. 1 mM.