Researchers use a common plastic additive to boost both the efficiency and stretchability of polymer OLED emitters

Researchers from the University of Chicago, Argonne National Laboratory and the University of Southern Mississippi have shown that a common, inexpensive plastic additive can simultaneously improve both the efficiency and the stretchability of polymer OLED emitter materials - two properties that have traditionally been at odds in stretchable display development.

The team, led by an undergraduate student, Sihong Wang, added small-molecule plasticizers - the same class of additives widely used to make commodity plastics soft and flexible - into polymer TADF OLED emitters. The plasticizer acts as a "molecular spacer" that increases the distance between the polymer chains. This spacing does two things at once: it suppresses triplet-exciton concentration quenching (which raises efficiency) and it improves chain mobility (which raises stretchability).

The researchers used dioctyl phthalate (DOP), a very common phthalate plasticizer, as their model additive. Applied to a representative TADF polymer (PDKCE), DOP raised the photoluminescence quantum yield (PLQY) from around 60% to approaching-unity levels of about 97%, while the external quantum efficiency (EQE) of rigid OLED devices increased from 9.3% to 12.6%. Importantly, the additive had little effect on charge transport and did not alter the emission spectrum.