Small Molecules for Vacuum-Processed Organic Photovoltaics: Past, Current Status, and Prospect

Organic photovoltaics (OPVs), a potential green technology that evolves to satisfy global energy demands, have shown great improvements recently. The success of OPVs relies on various endeavors, including new materials, protocols for morphology control, and device architectures. Vacuum deposition can produce OPVs that have precisely controlled multilayers and high stability suitable for commercialization. Molecular design plays a crucial role to fine tune the absorption, energy levels, and intermolecular interactions of organic materials for modulating the device performance. Researchers have extensively studied various combinations of judiciously selected or tailor-made donors (D) and acceptors (A) leading to small molecules with desired properties. In this review, vacuum-processable donor materials are collected and categorized into several sub-groups based on the connecting manner of D and A units. Molecular donors configured as D-A-A and A-D-A show better performance due to their long absorption and well-ordered molecular packing, which allow better light harvesting and charge transporting activities to obtain high short-circuit current density (JSC) and fill factor (FF). The progress of non-fullerene acceptors suitable for vacuum-deposited OPVs is also highlighted. Challenges and important prospects for future inventions of small molecules are discussed for better performance and commercialization of vacuum-processed OPVs.

Automated summary

Organic photovoltaics have shown significant improvements recently, with success relying on new materials, morphology control protocols, and device architectures. Vacuum deposition is highlighted as a method for producing OPVs with controlled multilayers and stability suitable for commercialization. Molecular design plays a crucial role in fine-tuning the absorption, energy levels, and interactions of organic materials for optimizing device performance.