Low-cost copper complexes as p-dopants in solution processable hole transport layers

Abstract

We demonstrate the usage of the Lewis-acidic copper(II)hexafluoroacetylacetonate (Cu(hfac)2) and copper(II)trifluoroacetylacetonate (Cu(tfac)2) as low-cost p-dopants for conductivity enhancement of solution processable hole transport layers based on small molecules in organic light emitting diodes (OLEDs). The materials were clearly soluble in mixtures of environmentally friendly anisole and xylene and spin-coated under ambient atmosphere. Enhancements of two and four orders of magnitude, reaching 4.0 × 10−11 S/cm with a dopant concentration of only 2 mol% Cu(hfac)2 and 1.5 × 10−9 S/cm with 5 mol% Cu(tfac)2 in 2,2′,7,7′-tetra(N,N-ditolyl)amino-9,9-spiro-bifluorene (spiro-TTB), respectively, were achieved. Red light emitting diodes were fabricated with reduced driving voltages and enhanced current and power efficiencies (8.6 lm/W with Cu(hfac)2 and 5.6 lm/W with Cu(tfac)2) compared to the OLED with undoped spiro-TTB (3.9 lm/W). The OLED with Cu(hfac)2 doped spiro-TTB showed an over 8 times improved LT50 lifetime of 70 h at a starting luminance of 5000 cd/m2. The LT50 lifetime of the reference OLED with PEDOT:PSS was only 8 h. Both non-optimized OLEDs were operated at similar driving voltage and power efficiency.

Lewis acids and bases as molecular dopants for organic semiconductors

“…44,47 BCF and copper(II)hexafluoroacetylacetonate were used as soluble p-dopants in solution processable hole transporting layers, effectively increasing their p-type conductivity. This directly gave rise to an enhanced current, power output, and long-term stability in the OLEDs, 53 and improved the power conversion efficiency of solar cells from 6.25 % to 13.93 %. 54 Lewis-acid interactions have also been shown to suppress phase separation in blended materials, thus allowing for better mixing of the electron donors and electron acceptors in solar cells.…”

Solvent Effects on the UV-Visible Absorption and Emission of Tris[4-Diethylamino)Phenyl]amine

“…The increased interest of researchers in field of OLED and OFET due to their wide application in optoelectronic devices [1,2]. Devices based on these materials are low weight and flexible cost effective devices which enhance their use in foldable devices as they provide large surface [3,4].…”

Compatibility of a Gaseous Dielectric with Al, Ag, and Cu and Gas‐Phase Synthesis of a New N‐Acylamidine Copper Complex

“…While many substituents (R 1 and R 2 in Figure ) have been introduced to N ‐acylamidines, none of them had strong electron withdrawing properties. Electron poor copper complexes have attracted our attention recently due to their excellent properties as conductivity dopants in organic electronic devices , . The most common way to obtain electron accepting properties in a complex is the introduction of one or more fluorine atoms on the ligand backbone.…”