Cartoon schematic illustrating how a pure self-assembled monolayer (SAM) tends to form micelles, leading to a loosely packed hole-selective layer (HSL), whereas the introduction of dispersants alongside the host SAM facilitates the formation of interspersed assembled monolayers (IAMs), resulting in a more compact and efficient HSL.
Since 2019, self-assembled monolayers (SAMs) composed of carbazole-based backbones with phosphonic acid anchoring groups have been widely applied in both organic solar cells (OSCs) and perovskite solar cells (PSCs).
However, to date, no study has reported a unified SAM strategy applicable to both OSCs and PSCs. This is mainly due to the distinct mechanisms governing the photovoltaic effects in these two systems, which lead to different interfacial requirements for SAMs.
In this study, we present—for the first time—a universal approach using interspersed assembled monolayers (IAMs) to address critical interface challenges in both emerging solar cell technologies, achieving a "kill two birds with one stone" solution.
The concept of IAMs is based on introducing a secondary molecule structurally similar to the host SAM backbone but possessing a stronger intramolecular push–pull effect and a higher dipole moment. This design not only suppresses undesirable micelle formation of the host SAM but also enhances hole extraction efficiency.
Moreover, we systematically investigated the impact of side chains on the performance of IAMs and discovered that the steric hindrance of the side chains also plays a crucial role in suppressing micelle formation.
Finally, by implementing IAMs, we improved the power conversion efficiency (PCE) of OSCs from 18.12% to 19.23%, and PSCs from 23.84% to 25.01%, while simultaneously enhancing device stability.
“The greatest value of this work lies in providing a universal chemical solution, sparing scientists and engineers from struggling with dispersant design, and significantly reducing R&D costs—ultimately accelerating the realization of net-zero carbon emissions,” says corresponding author Dr. Pi-Tai Chou, professor of chemistry at the College of Science at National Taiwan University.
Prof. Pi-Tai Chou’s email address: [email protected]
