TY - JOUR
T1 - Performance and lifetime of vacuum deposited organic light-emitting diodes
T2 - Influence of residual gases present during device fabrication
AU - Wölzl, F.
AU - Rabelo De Moraes, I.
AU - Lüssem, B.
AU - Hofmann, S.
AU - Leo, K.
AU - Gather, M.C.
PY - 2014/11/1
Y1 - 2014/11/1
N2 - Understanding the influence of residual gases present during vacuum deposition of organic light-emitting diodes (OLEDs) and their effect on the device lifetime and the electrical characteristics of OLEDs is crucial for advancing industrial fabrication. In order to gain a more in-depth understanding, the influence of residual nitrogen, oxygen, and water vapor on lifetime and electrical characteristics is investigated. This is achieved by introducing the residual gases into the evaporation chamber through a needle valve while monitoring the partial pressures with the help of a mass spectrometer. We find that water vapor introduces a series resistance to the OLED while the other gases do not influence the electric characteristics. The presence of oxygen or nitrogen impacts the lifetime of the OLEDs by the same amount. Water vapor introduces an additional, even faster degradation process within the first hours of OLED operation. The electrically stressed OLEDs are analyzed by laser desorption/ionization time-of-flight mass spectroscopy. We identify the dimerisation of BPhen as well as the complexation reaction of α-NPD with an Ir(piq) fragment as sources of device degradation.
AB - Understanding the influence of residual gases present during vacuum deposition of organic light-emitting diodes (OLEDs) and their effect on the device lifetime and the electrical characteristics of OLEDs is crucial for advancing industrial fabrication. In order to gain a more in-depth understanding, the influence of residual nitrogen, oxygen, and water vapor on lifetime and electrical characteristics is investigated. This is achieved by introducing the residual gases into the evaporation chamber through a needle valve while monitoring the partial pressures with the help of a mass spectrometer. We find that water vapor introduces a series resistance to the OLED while the other gases do not influence the electric characteristics. The presence of oxygen or nitrogen impacts the lifetime of the OLEDs by the same amount. Water vapor introduces an additional, even faster degradation process within the first hours of OLED operation. The electrically stressed OLEDs are analyzed by laser desorption/ionization time-of-flight mass spectroscopy. We identify the dimerisation of BPhen as well as the complexation reaction of α-NPD with an Ir(piq) fragment as sources of device degradation.
U2 - 10.1016/j.orgel.2014.07.014
DO - 10.1016/j.orgel.2014.07.014
M3 - Article
AN - SCOPUS:84908029354
SN - 1566-1199
VL - 15
SP - 3251
EP - 3258
JO - Organic Electronics
JF - Organic Electronics
IS - 11
ER -