Contact formation at the C60/alkali-metal fluoride/Al interface

Abstract

Efficient contact formation is critical in organic electroluminescence and photovoltaic devices that utilize fullerene (C60). Unlike traditional electron transport molecules, such as tris-(8-hydroxy-quinolinato)aluminum (Alq3), C60 is found to be highly selective of injection layers. Charge injection properties of alkali-metal fluoride injection layers at the C60∕Al cathode interface of organic light emitting diodes were studied. LiF is found to be unique amongst the alkali-metal fluorides in producing an Ohmic contact. The device performance is strongly linked to the size of the vapor phase fluoride molecules. The observed phenomena are explained by an intercalation region at the metal/organic interface.

Effects of cathode buffer layers on the efficiency of bulk-heterojunction solar cells

“…It had been reported that the dissociation of LiF would improve the charge-transfer process at organic/metal interface and the mechanisms were demonstrated to be band bending within the organic layer or interface dipoles. 15,16 On the other hand, bathocuproine ͑BCP͒ is also extensively used well as a buffer layer in light-emitting diodes ͑LEDs͒ and small molecule organic solar cells because of its holeblocking and electron-transporting functions. 17,18 Generally speaking, the thickness of BCP as the buffer layer is usually larger than 10 nm.…”

C60:LiF Blocking Layer for Environmentally Stable Bulk Heterojunction Solar Cells

“…Theory and experiment have confi rmed that LiF is critical to forming an ohmic contact between C 60 and Al. [36][37][38] To balance the need for a percolative path of C 60 molecules through the composite, with the need for suffi cient LiF at the cathode interface to for an ohmic contact, the concentration of LiF should therefore be kept around 80%.…”

Efficient bilayer phosphorescent organic light-emitting diodes: Direct hole injection into triplet dopants

“…12 Substrates were ultrasonically cleaned with a standard regiment of Alconox®, acetone, and methanol followed by ultraviolet ozone treatment. The cathode for all devices was LiF ͑1 nm͒/Al ͑100 nm͒.…”