Color tunable metal-cavity organic light-emitting diodes with fullerene layer

Three primary colors, red, green, and blue have been obtained from a single-emission layer organic light-emitting diode (OLED) through optical design using a half-wavelength all-metal-cavity device. Fullerene is used as an electron transport layer to further enhance the electrical performance of the cavity device and the optical tuning of the cavity OLED. This fullerene layer results in a $∼2V$ driving voltage reduction and a $∼20%$ increase in power efficiency, as compared with traditional cavity OLED with Alq as the electron transport layer. The emissive spectra for the cavity OLEDs are well predicted by the Fabry–Perot cavity theory. The spectral narrowing and intensity enhancement at the resonance wavelength have been observed and are explained by the redistribution of optical-mode density inside the microcavity. Schemes to tune the emissive color by varying the cavity length through variations of indium tin oxide thickness, hole transport layer thickness, and electron transport thickness, individually or collectively, have been proposed and demonstrated.