Sterically Engineered Polymeric HTM with Suppressed Torsion for High-Efficiency and Long-Lifetime Solution-Processed OLEDs

Abstract

Achieving both high efficiency and operational stability in solution-processed organic light-emitting diodes (OLEDs) remains a significant challenge due to charge imbalance and the limited structural robustness of polymeric hole transport layers (HTLs). Herein, we report a sterically engineered polymer HTM, TFPHS, designed by incorporating a bulky 1-methyl-4-phenylnaphthalene side group into a TFB-derived conjugated backbone. This structural modification enhances backbone rigidity, suppresses dihedral torsion, and enables balanced hole and electron transport. Devices employing TFPHS exhibit a peak external quantum efficiency of 24% and an extended LT₉₅ lifetime of over 215 h at 1000 cd m^–2, substantially outperforming TFB-based counterparts. In-situ Raman spectroscopy, supported by density functional theory (DFT) calculations, reveals that improved photochemical stability stems from the inhibited reorganization of triphenylamine segments. Additionally, TFPHS films display improved morphology and wettability, facilitating a uniform emissive layer formation. This work establishes a clear structure–property–performance relationship and offers a rational design strategy for high-performance polymer semiconductors in solution-processed OLEDs and other optoelectronic applications.