TY - JOUR
T1 - Mechanistic description of the efficiency loss in organic phosphorescent host–guest systems due to triplet-polaron quenching
AU - Ligthart, Arnout
AU - Nevels, Teun D.G.
AU - Weijtens, Christ H.L.
AU - Bobbert, Peter A.
AU - Coehoorn, Reinder
PY - 2021/4
Y1 - 2021/4
N2 - In this study we demonstrate how a mechanistic description can be obtained of the interplay of all processes that give rise to the efficiency loss due to triplet polaron quenching (TPQ) in phosphorescent host-guest systems such as used in organic light-emitting diodes (OLEDs). We study unipolar devices with an emissive layer consisting of m-MTDATA:Ir(ppy)2(acac), in which excitons on the phosphorescent Ir(ppy)2(acac) molecules are quenched by holes on the m-MTDATA host. The final TPQ-process is disentangled from all other relevant processes, such as polaron and exciton diffusion and field-induced exciton dissociation, by carrying out a combination of electrical, photoluminescence (PL) and field-induced dissociation experiments. The analysis is supported by carrying out kinetic Monte Carlo simulations. We find that a conventional approach, within which the loss is phenomenologically quantified using a rate coefficient, cannot consistently describe all experimental results. For a wide temperature range a fair mechanistic description of all results is obtained when using a TPQ Förster radius of 3.8 nm and a triplet exciton binding energy of 0.9 eV.
AB - In this study we demonstrate how a mechanistic description can be obtained of the interplay of all processes that give rise to the efficiency loss due to triplet polaron quenching (TPQ) in phosphorescent host-guest systems such as used in organic light-emitting diodes (OLEDs). We study unipolar devices with an emissive layer consisting of m-MTDATA:Ir(ppy)2(acac), in which excitons on the phosphorescent Ir(ppy)2(acac) molecules are quenched by holes on the m-MTDATA host. The final TPQ-process is disentangled from all other relevant processes, such as polaron and exciton diffusion and field-induced exciton dissociation, by carrying out a combination of electrical, photoluminescence (PL) and field-induced dissociation experiments. The analysis is supported by carrying out kinetic Monte Carlo simulations. We find that a conventional approach, within which the loss is phenomenologically quantified using a rate coefficient, cannot consistently describe all experimental results. For a wide temperature range a fair mechanistic description of all results is obtained when using a TPQ Förster radius of 3.8 nm and a triplet exciton binding energy of 0.9 eV.
KW - Field-induced dissociation
KW - Kinetic Monte Carlo simulations
KW - Organic light-emitting diodes
KW - Organic semiconductors
KW - Roll-off
KW - Triplet-polaron quenching
UR - http://www.scopus.com/inward/record.url?scp=85100414676&partnerID=8YFLogxK
U2 - 10.1016/j.orgel.2020.106058
DO - 10.1016/j.orgel.2020.106058
M3 - Article
AN - SCOPUS:85100414676
VL - 91
JO - Organic Electronics
JF - Organic Electronics
SN - 1566-1199
M1 - 106058
ER -