Magneto-conductance (MC) was used as a fingerprint detection tool to contactlessly visualize high-temperature evolution processes of exciplex (EX) states in theTBRb/C_(60) planar-heterojunction (PHJ) organic light-emittingdiodes (OLEDs). Specifically, MC was used to contactlesslyobserve at room temperature around 300 K. The reverse intersystem crossing (RISC) process from triplet to singlet EXstates (EX_(3) → EX_(1)) in the device at 300 K is observed for thefirst time from the TBRb/C_(60) PHJ-OLED. The device shows ahalf-band-gap turn-on photoelectric characteristics. Temperature-dependentMC traces of the device present an interesting conversion from RISC to triplet-charge annihilation(TQA) process between EX_(3) and charge carriers (T_(1) + q → e + h+ q′) after the device temperature increasing from 300 to 425 Kvia in-situ heating. By comprehensively analyzing MC traces,current-voltage characteristic curves, transient electroluminescence spectra, and optical microscopy images of thedevice and atomic force microscopy images of the TBRb film,we find that the increase of temperature destroys the moleculestructures of organic materials, which leads to the generationof many traps inside the organic semiconductor films comprising the TBRb/C_(60) PHJ-OLED. These traps will capturepolaron-pairs, EX, and exciton states and then affect theirinteractions, which finally induces the changes of MC traces.This work not only deepens understandings of high-temperatureevolution processes of polaron-pairs, EX, and excitonstates in the TBRb/C_(60) PHJ devices, but also provides a newmethod to study the microscopic mechanisms in OLED operating in high temperature environment.
