Abstract
AbstractBimolecular exciton‐quenching processes such as triplet–triplet annihilation (TTA) and triplet–polaron quenching play a central role in phosphorescent organic light‐emitting diode (PhOLED) device performance and are, therefore, an essential component in computational models. However, the experiments necessary to determine microscopic parameters underlying such processes are complex and the interpretation of their results is not straightforward. Here, a multiscale simulation protocol to treat TTA is presented, in which microscopic parameters are computed with ab initio electronic structure methods. With this protocol, virtual photoluminescence experiments are performed on a prototypical PhOLED emission material consisting of 93 wt% of 4,4ʹ,4ʺ‐tris(N‐carbazolyl)triphenylamine and 7 wt% of the green phosphorescent dye fac‐tris(2‐phenylpyridine)iridium. A phenomenological TTA quenching rate of 8.5 × 10−12 cm3 s−1, independent of illumination intensity, is obtained. This value is comparable to experimental results in the low‐intensity limit but differs from experimental rates at higher intensities. This discrepancy is attributed to the difficulties in accounting for fast bimolecular quenching during exciton generation in the interpretation of experimental data. This protocol may aid in the experimental determination of TTA rates, as well as provide an order‐of‐magnitude estimate for device models containing materials for which no experimental data are available.
Highlights
Low-cost organic materials with technological relevance are key constituents of a wide range of devices such as organic light emitting diodes (OLEDs),[1] organic necessary to determine microscopic parameters underlying such processes photovoltaics,[2] and organic field effect are complex and the interpretation of their results is not straightforward.transistors.[3]
We model photoluminescence quenching in comparison to photoluminescence measurements in a prototypical OLED emission material consisting of 93 wt% of TCTA and 7 wt% of the green phosphorescent dye Ir(ppy)3.[17]. Microscopic rates for triplet annihilation (TTA) and exciton transport were computed from first principles, based on an atomistic morphology generated with Deposit, as described in the Experimental Section
We analyzed TTA in an OLED emission layer comprising TCTA doped with the phosphorescent emitter Ir(ppy
Summary
Low-cost organic materials with technological relevance are key constituents of a wide range of devices such as organic light emitting diodes (OLEDs),[1] organic necessary to determine microscopic parameters underlying such processes photovoltaics,[2] and organic field effect are complex and the interpretation of their results is not straightforward. Since kTT is a material-specific constant, this variation indicates that the lack of direct experimental access to [nex](0) limits accuracy of the determination of TTA rates These problems are absent in theoretical approaches, where the triplet density can be initialized instantaneously, but the accuracy of theoretical methods to compute the rates must be validated. We validate such a methodology for the analysis of exciton quenching: using a KMC simulation of exciton dynamics, where the exciton density [nex](t) is directly accessible at all times, we perform virtual photoluminescence experiments on a digital twin of a guest–host material comprising the phosphorescent dye Ir(ppy) in a matrix of host molecules of 4,4′,4′′-tris(N-carbazolyl)triphenylamine (TCTA) starting from first principles
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
