Electronic and chemical properties of cathode structures using 4,7-diphenyl-1,10-phenanthroline doped with rubidium carbonate as electron injection layers

Abstract

Electron mobility of 4,7-diphyenyl-1,10-phenanthroline estimated by using space-charge-limited currentsThe electronic properties and chemical interactions of cathode structures using 4,7-diphenyl-1, 10-phenanthroline ͑Bphen͒ doped with rubidium carbonate ͑Rb 2 CO 3 ͒ as electron injection layers were investigated. Current-voltage characteristics reveal that the devices with Bphen/ Rb 2 CO 3 / Al as cathode structures possess better electron injection efficiency than those with cathode structures of Bphen/LiF/Al. Ultraviolet and x-ray photoemission spectroscopy shows that n-type doping effects resulting from Rb 2 CO 3 and the gap states created by aluminum deposition are both keys to the improved carrier injection efficiency. Moreover, theoretical calculation indicates that the chemical reaction between aluminum and the nitrogen atoms in Bphen is the origin of the gap states.

Blue Phosphorescent Organic Light‐Emitting Diodes Using an Exciplex Forming Co‐host with the External Quantum Efficiency of Theoretical Limit

“…mCP and B3PYMPM were selected as for the HTM and the ETM, respectively and also used as an exciplex forming co‐host in EML because they have higher triplet energy than FIrpic. ReO 3 doped mCP and Rb 2 CO 3 doped B3PYMPM were used as the hole and electron injection layers, respectively . The doping concentrations were experimentally optimized to 4 wt% in charge injection layers.…”

Correlation of energy band alignment and turn-on voltage in organic light emitting diodes

“…The detailed experimental setup of UPS has been described in the previous reports. 9,10 The dependence of the turn-on voltage on thickness was first investigated. Devices were fabricated with N,NЈ-di͑naphthalene-1-yl͒-N,NЈ-diphenylbenzidine ͑NPB͒ of identical thickness as HTLs and tris͑8-hydroxyquinoline͒ aluminum ͑Alq 3 ͒ of various thickness as ETLs.…”

Understanding the Role of Phenanthroline as Interlayer in Bulk Heterojunction Organic Photovoltaic Cells

“…In accordance to results from other authors indicating that thermally evaporated Li can diffuse up to several dozens of nanometers in thermally evaporated layers of BCP or BPhen, we suggest that, in our samples, LiF or its dissociated species (Li + and F − ) diffuse throughout the BPhen layer to raise the conductivity in the bulk rather than only at the interface. N‐type doping of BPhen was also suggested to occur in thermally evaporated BPhen/RbCO 3 structures where a thin layer (1 nm) of RbCO 3 is deposited over a thick (80 nm) BPhen layer on the basis of J ‐ V characteristics of devices and analysis from ultraviolet and X‐ray photoemission spectroscopies (UPS and XPS).…”

“…BCP and BPhen were also used as electron transporting layers (ETL) in organic light‐emitting devices (OLEDs) because they combine transparency in the visible spectrum (energy gaps of about 3.5 eV) with high electron mobilities (∼10 −4 cm 2 V −1 s −1 in BPhen and ∼10 −6 cm 2 V −1 s −1 in BCP). Several BPhen and BCP n‐doped layers (e. g. Rb 2 CO 3 doped BCP) were introduced in OLEDs to form an ohmic interface with the cathode and improve devices efficiency …”