The wide use of organic light-emitting diodes (OLEDs) is materializing as devices exhibit enhanced performance. Attention has been placed on finding quality solution-processable organic semiconducting materials amenable to low cost processing via solution-based fabrication methods. The high solubility and good film formability intrinsic to polymers have led to their use in the majority of solution-processed devices. Recently, attention has shifted to the incorporation of small molecules into solution-processed devices. With this focus, we gain the high efficiency of small molecules as well as the ease of fabrication by solution-processing. Research has also been aimed at developing materials with efficient and stable red, green, and blue emission necessary for full color displays. OLEDs in the ultraviolet are attractive for analytical applications, including compact sensors and on-chip spectrometers. Particularly of interest for analytical applications are narrow-band multi-color microcavity OLED arrays, which can be used in on-chip spectrometers or in multianalyte chemical or biological sensing. In this dissertation, novel solution-processed device structures are demonstrated, including the hitherto unexplored structure of polymer guest:small molecule host OLEDs and a UV-to-blue multi-color microcavity OLED array based on a mixed emitting layer. Also included are investigations into new materials and discussions on the origins of improvements.