Properties of 2,6-di-tert.-butyl-4-(2,5-diphenyl-3,4-dihydro-2H-pyrazol-3-yl)-phenol as hole-transport material for life extension of organic light emitting diodes

We studied structural and optical properties of 5′ replaced pyrazoline by hindered phenol 2,6-di-tert.-butyl-4-(2,5-diphenyl-3,4-dihydro-2H-pyrazol-3-yl)-phenol (HPhP) films for application in organic light-emitting diode (OLED) as a hole transport layer (HTL). Analysis of impedance and current–voltage characteristics of ITO/HPhP/Al structure has shown that the current is limited by a space charged region with exponential distribution of traps near Fermi level. Characteristics of electroluminescence structure ITO/HPhP/Alq3/poly(ethylene glycol) dimethyl ether/Al was studied and analyzed. We performed the comparative analysis of luminescence time decay in two types of electroluminescent devices with HTL from pyrazolines derivative with hindered phenol and without it. We showed that hindered phenol in HTL slows down the degradation processes in OLED.

► 5′ replaced pyrazoline by hindered phenol films for application in OLED were studied. ► We showed that hindered phenol in HTL slows down the degradation processes in OLEDs. ► OLED device has turn-on voltages 6.4 V, and exhibit high current efficiency values (9.75 cd/A).