In:
SID Symposium Digest of Technical Papers, Wiley, Vol. 53, No. S1 ( 2022-10), p. 202-207
Abstract:
With the increase of user demand, higher brightness become a trend for the information display products, which makes efficiency roll‐off issue even more concerning in organic light‐emitting diodes (OLED). Here, we fabricated a set of red phosphorescent OLED structure for investigating the origin of roll‐off. By replacing different kinds of red dopant materials (RD‐1 and RD‐2) and red host materials, we found the main reason affecting efficiency roll‐off is dopant materials in emitting layer. Three key factors, including triplet‐triplet annihilation (TTA), triplet‐polaron quenching (TPQ), as well as the width of recombination zone were investigated. Firstly, the transient photoluminescence (PL) and electroluminescence (EL) results illustrated a longer excited state lifetime for RD‐2. Consequently, we demonstrated a relatively serious TPQ phenomenon in the unipolar device with RD‐2, which revealed a higher interaction probability between photon‐induced exciton and polaron. Finally, the OLED with RD‐2 showed apparently higher SCLC (space charge limited current) hole mobility in the hole‐only device. According to the recombination zone profiles and capacitance results, we proposed that a higher hole‐type space charge concentration in the device based on RD‐2 contributed to a higher polaron and triplet concentration in EML. Combined with a longer exciton diffusion length, a higher rate of TPQ was induced and resulted in relatively serious roll‐off phenomenon.
Type of Medium:
Online Resource
ISSN:
0097-966X
,
2168-0159
Language:
English
Publisher:
Wiley
Publication Date:
2022
detail.hit.zdb_id:
2526337-7
