Organic optoelectronics has experienced tremendous growth in recent decades. Many new materials exhibiting unique electronic and optical properties were developed and studied. The deep understanding of the fundamental properties of these materials was combined with the device engineering methods to create a wide variety of optoelectronic devices, where light is used to affect electronic processes or vice versa, thus providing useful functionality. In this dissertation, the devices exhibiting light-harvesting and light-emitting properties are discussed. Devices of the first type are light-absorbing and convert optical energy into electrical form. These devices may be used for energy sourcing purposes, as it is realized in photovoltaics, or for light sensing, as in photodetectors. In this part of the dissertation, I discuss new DA4-type electron acceptors and their applications in binary and ternary blend bulk heterojunction solar cells. Power conversion efficiencies of more than 10% were demonstrated and rationalized in the best-performing ternary devices. In addition, an approach of using ternary bulk heterojunction blends to reduce the dark current in organic photodetectors is discussed in Chapter 4. In the part where I discuss light-emitting devices, the main focus is on light-emitting field-effect transistors (OLET) – an emerging class of devices that has great potential and numerous benefits compared to traditional OLEDs. I discuss new fluorescent semi-ladder foldamer polymers, their structural and optical properties, as well as, their applications as emissive materials in OLET devices.