## 3 Organic Light Emitting Field Effect Transistors (OLEFETs)
Moreover, such an arrangement of TDMs serves to mitigate the light transmission effect, thereby amplifying the device's performance. This study marks the inaugural practical application of these concepts in an OLEFET. Utilizing a thiophene-phenylene co-oligomer, specifically 1,4-bis[5-[4-(trimethylsilyl)phenyl]]thiophen-2-yl]benzene (4) (Figure 8), featuring trimethylsilyl (TMS) terminal substituents, facilitated the promotion of in-plane TDM orientation during the growth of highly emissive semiconductor single crystals. OLEFETs constructed from derivative 4 exhibited ambipolar charge transport coupled with efficient electroluminescence, while the single-crystal devices showcased linearly polarized electroluminescence with a polarization degree of 0.78 \(\pm\) 0.06 [49]. The observed polarization characteristics of both electro- and photoluminescence align seamlessly with the resolved crystal structure and corresponding calculations. These findings underscore the potential of strategically controlling in-plane ordered TDMs via molecular packing as a promising avenue for crafting materials tailored for highly efficient light-emitting electronic devices. As demonstrated by the final example in this brief review, [PERSON] and colleagues presented an intriguing white OLEFET in 2024 with full emission properties [50]. In their study,  
Figure 8: Chemical structure of 1,4-bis[5-[4-(trimethylsilyl)phenyl]]thiophen-2-yl]benzene (4) employed as OLEFET by [PERSON] and col [49]. Figure 7: (**a**) Chemical structure of 2,7-diphenyl-9H-fluorene (**3**) for the construction of the OLEFET described by [PERSON] and col. (**b**) Transfer plots of the OLEFET from (**3**) with its electroluminescence image by CCD camera. (**c**) Output plot of nanowire single crystal of (**3**)-based OLEFET. Image taken from reference [48]. they introduced a high-performance white OLEFET that reached an external quantum efficiency (EQE) close to 13.9%. This impressive result was achieved through a unique planar-integrated device structure, featuring an active layer composed of mCP:Flrpic:rubrene (Figure 9). The exceptional efficiency of these OLEFETs is largely due to efficient exciton management, improved light extraction, and minimized quenching by positioning the exciton recombination zone away from the source electrode within the lateral-integrated configuration. It is expected that further advancements in OLEFET performance will be realized through a deeper understanding of the device's operating mechanisms, along with optimization of the fabrication process by incorporating better emissive materials, ensuring balanced electron-hole injection and transport, and enhancing both exciton management and light extraction. Additionally, the successful development of white OLEFET arrays for full-color displays represents a significant step forward in their application for advanced display technologies. This progress also opens the door to novel research directions, such as stretchable OLEFETs, spin-OLEFETs, on-chip optoelectronic integration circuits, and potentially high-density stretchable visual sensors. However, there are several challenges that OLEFETs must address in the coming years to advance their development. These challenges require careful consideration and resolution. One major difficulty is the development of high-efficiency systems, which is hindered by the limited availability of organic small molecules with high electron and hole mobility, leading to a scarcity of OLEDs. Additionally, achieving low-bias, high-performance OLEFET devices is crucial for the technology's progress. OLEFETs generally exhibit lower EQE compared to OLEDs, and improving this parameter is essential. The electroluminescence process in ambipolar OLEFETs remains ambiguous and not well understood. Furthermore, research on n-type OLEFETs is limited. There has been insufficient specialized investigation into n-type OLEFETs, with existing studies mainly focusing on light emission from the semiconductor layer.