Self-Assembled Interlayer Enables High-performance Organic Photovoltaics with Power Conversion Efficiency Exceeding 20.

Interfacial layers (ILs) are prerequisites to form the selective charge transport for high-performance organic photovoltaics (OPVs), but mostly result in considerable parasitic absorption loss. Trimming the ILs down to a mono-molecular level via the self-assembled monolayer (SAM) is an effective strategy to mitigate parasitic absorption loss. However, such strategy suffers from inferior electrical contact with low surface coverage on rough surface and the poor producibility. To address these issues, here we develop the self-assembled interlayer (SAI) strategy, which involves a thin layer of 2-6 nm to form a full coverage on substrate via both covalent and Van de Waals bonds by using a self-assembled molecule of 2-(9H-carbazol-9-yl) (2PACz). Via the facile spin coating without further rinsing and annealing process, it not only optimizes the electrical and optical properties of OPVs, which enables a world-record efficiency of 20.17% (19.79% certified), but also simplified the tedious processing procedure. Moreover, the SAI strategy is especially useful to improve the absorbing selectivity for semi-transparent OPVs, which enables a record light utilization efficiency of 5.34%. Our work provides an effective strategy of SAI to optimize the optical and electrical properties of OPVs for high performance and solar window applications. This article is protected by copyright. All rights reserved.