Imidazole-Functionalized Imide Interlayers for High Performance Organic Solar Cells

Abstract

Imidazole-functionalized naphthalene diimide and perylene diimide were efficiently synthesized at low cost and used as versatile cathode interlayers in organic solar cells. These imidazole-functionalized small molecules show high electron affinity and conductivity and efficiently reduce the work function of air-stable metal electrodes, removing the energy barriers of electron transport in organic electronic devices. Compared to widely used amine-functionalized small-molecule cathode interlayers, the crystallinities of imidazole-functionalized molecules were moderately suppressed, affording good film-forming properties. The substitution of amine with the imidazole group is a simple and powerful strategy to improve both film morphology and charge transport of imide-based small-molecule interlayer materials. The imidazole-functionalized interlayers are compatible with numerous active layers in solar cells, affording high efficiencies over a wide thickness range from ∼5 nm to ∼33 nm, with a maximum efficiency of 17.98%, showing promising applications in organic electronics.

Boosting the Efficiency of Non-fullerene Organic Solar Cells via a Simple Cathode Modification Method

“…After the development of the milestone small molecule acceptor, Y6, and its derivatives, interfacial engineering, in particular, the research on ETLs with compatible properties has been trending. New ETL materials have been synthesized and adopted, which promoted both the PCE and stability of the Y6-based devices. − Behind the improved device performance was progress of the ETL made from the material design and synthesis that leads to novel material structures. − However, compared to the doping strategy widely used in improving the property of the hole transport layers (HTLs) that also leads to outstanding results, − the chemistry input in material synthesis could be cost inefficient and should be accompanied by exploring methods of utilizing existing ETL materials.…”

Perylene‐diimide‐based cathode interlayer materials for high performance organic solar cells

“…Imidazole‐functionalized perylene diimide, namely, PDI‐M (Figure 6), was developed by Liu et al. in 2021 66 . PDI‐M showed high conductivity and can efficiently reduce the WF of air‐stable metal electrodes.…”

Hole/Electron Transporting Materials for Nonfullerene Organic Solar Cells

“…Note that the excessive aggregation of PDI may lead to adverse effect on film forming properties. To balance the aggregation and film morphology, Liu et al introduced bulky imidazole to the side chains of PDI and developed PDI-M. [54] Compared with the amine end group functionalized PDI-N, the bulky imidazole attached on to the tail of the alkyl chain of PDI-M moderately reduced the crystallinity and aggregation, imparting PDI-M with good filmforming abilities. The efficient self-doping, preferred molecule orientation and packing led to better charge transport characteristics of PDI-M.…”

“…To balance the aggregation and film morphology, Liu et al. introduced bulky imidazole to the side chains of PDI and developed PDI‐M [54] . Compared with the amine end group functionalized PDI‐N, the bulky imidazole attached on to the tail of the alkyl chain of PDI‐M moderately reduced the crystallinity and aggregation, imparting PDI‐M with good film‐forming abilities.…”