High Color Rendering Index Solution-Processed White OLEDs Based on Novel Exciplexes

Organic light-emitting diodes (OLEDs) are increasingly vital in display and lighting technology due to their self-emission, high contrast, rapid response, and solution processability. Conventional white OLEDs, reliant on combining complementary colors, often involve complex structures and material losses during evaporation. Alternatively, the exciplex, formed by donor–acceptor molecular interactions, offers simplified designs and tunable emission. However, the emission mechanisms of exciplex remain underexplored. Additionally, the achievement of high-quality white exciplex emission is a significant challenge. Here, this study investigates binary donor-acceptor systems, pairing donors (small molecules CBP, TCTA; polymers PVK, PTAA) with the acceptor TpPyPb, to fabricate solution-processed OLEDs with simplified architectures. Exciplex formation is validated by using a modified Rehm–Weller equation to assess Gibbs free energy, complemented by spectroscopic analysis to elucidate formation mechanisms. Remarkably, a novel bulk exciplex system, PTAA: TpPyPb, yields a high-quality white emission with a color rendering index (CRI) of 84, which is among the highest for solution-processed exciplex-based OLEDs. Polymeric donors demonstrate more discrete charge-transfer state energies, which facilitate broader spectral emission, making them ideal for white exciplex and host materials. This work provides critical insights into exciplex emission mechanisms and advances the development of high-performance, solution-processed white OLEDs, offering a pathway to simplified, efficient, and high-quality lighting and display technologies.