Polaritons, hybrid light–matter quasiparticles formed under strong coupling, have emerged as a promising platform to reshape molecular energy landscapes and enable room-temperature control of photophysical processes. Yet despite substantial progress, polariton-based devices still trail state-of-the-art optoelectronics. This gap in polaritronics motivates this dissertation to translate polaritonic design principles into high-performance organic optoelectronic devices.
First, time-resolved electroluminescence in polaritonic organic light-emitting diodes is used to identify the origin of delayed emission under electrical drive. Despite large Rabi splittings and systematic tuning of the lower polariton relative to the triplet manifold, the delayed component is dominated by trap-assisted emission, with no resolvable polariton-enabled triplet harvesting under the measured conditions. This highlights the collective, delocalized nature of polaritons as a key limitation for modifying intramolecular kinetics in these devices.
Building on these insights, the thesis pivots to device-scale polaritonic engineering. For organic photodiodes, non-fullerene acceptors are embedded in a microcavity to form polaritons, delivering narrowband, angle-stable responsivity by operating the lower polariton on the low-absorption tail, where its excitonic fraction suppresses angular dispersion while maintaining useful responsivity. The result is a tunable, intrinsically selective passband with markedly reduced angular shift compared with conventional cavity organic photodiodes.
For near-infrared organic light-emitting diodes, a broadband deep-red emitter is combined with a strong-coupling layer in a frst-order microcavity. The resulting devices exhibit lower polariton-dominated electroluminescence with competitive effciencies. Furthermore, emission bandwidths are substantially narrower than typical near-infrared organic devices, concentrating emission in the near-infrared.
Also, strong coupling and lower-polariton emission have been realised in hybrid and fully solution-processed DBR microcavities.
Overall, the work clarifes when polaritons do not alter microscopic relaxation pathways in organic light-emitting diodes, and shows how polaritonic engineering nevertheless delivers practical gains, namely, narrowband, angle-independent organic photodiodes and record-class near-infrared organic light-emitting diodes effciencies, thereby bridging fundamental polariton science and device performance.