## 3 Material Systems
The incorporation of poly(methyl methacrylate) (PMMA) into conjugated polymer systems has proven effective in reducing aggregation-induced quenching and improving film formation properties, as demonstrated in blends with polyfluorene derivatives, as illustrated in Figure 2[62; 63]. However, the development of effective polymer blends faces several challenges. The primary limitation stems from the thermodynamic immiscibility of many polymer pairs, leading to phase separation at various length scales. For example, while PFO and F8 BT can form relatively stable blends at certain compositions, phase separation often occurs during thermal annealing, affecting device stability [64; 65; 66]. While controlled phase separation can sometimes be beneficial, creating specific morphologies for optimal device performance, uncontrolled segregation often leads to poor device performance and stability. The compatibility of polymer blends depends strongly on their molecular structure, molecular weight, and processing conditions. Even small changes in processing parameters can significantly affect blend morphology. Solutions to these challenges include the use of compatibilizers, such as block copolymers that can stabilize the interface between immiscible components, careful selection of common solvent systems that enable uniform mixing during processing, and the development of processing protocols that kinetically trap desired morphologies. For instance, the addition of small amounts of rod-coil block copolymers has been shown to stabilize blends of conjugated polymers with insulating matrices [67; 68; 69]. Additionally, the optical properties of blends can be affected by energy transfer between components, requiring careful consideration of energy level alignment and spatial distribution of the constituents. Forster resonance energy transfer (FRET) between donor and acceptor polymers can be either beneficial or detrimental depending on the application, necessitating precise control over blend composition and morphology to achieve desired optical properties [70; 71; 72]. Besides blends of organic materials, the hybrid organic-inorganic systems offer another alternative approach. The integration of organic polymers with inorganic nanostructures has emerged as a promising approach to creating materials with enhanced or complementary functionalities. Semiconductor quantum dots (QDs) can be incorporated into polymer matrices to achieve spectrally tunable emission through quantum confinement effects. For example, CdSe/ZnS core-shell quantum dots embedded in MEH-PPV matrices have demonstrated efficient energy transfer from the polymer to QDs, resulting in enhanced red emission useful for display applications [73; 74]. Similarly, PbS quantum dots integrated with polyfluorene derivatives have enabled near-infrared emission and detection capabilities, extending the spectral range of polymer-based devices [75]. Another successful implementation includes hybrid systems of P3 HT with zinc oxide nanoparticles, where the inorganic component enhances charge transport while maintaining the solution processability of the polymer matrix [76]. Metal nanoparticles introduce localized surface plasmon resonance (LSPR) effects, which can enhance light absorption and emission through near-field coupling. Gold and silver nanoparticles are particularly useful due to their strong plasmonic responses in the visible region [77]. For instance, silver nanoparticles embedded in F8 BT have shown significant enhancement of photoluminescence through plasmonic coupling [78]. The enhancement of local electromagnetic fields near metal nanoparticles can increase the efficiency of nonlinear optical processes and modify emission rates through the Purcell effect [79; 80]. However, successful implementation of these hybrid systems requires care  
Figure 2: Laser confocal microscopy images of 5 wt% polyfluorene derivative/PMMA blend ES nanofibers with (**a**) PFO; (**b**) PFO; (**c**) PFBT; (**d**) PFTP [62]. Reprinted (adapted) with permission from [62].