###### Abstract  
This review examines the distinct advantages of organic semiconductors over conventional insulating polymers as optically active materials in photonic applications. We analyze the fundamental principles governing their unique optical and electronic properties, from basic conjugated polymer systems to advanced molecular architectures. The review systematically explores key material classes, including polyfluorenes, polyphenylene vinylenes, and polythiophenes, highlighting their dual electrical-optical functionality unavailable in passive polymer systems. Particular attention is given to polymer blends, composites, and hybrid organic-inorganic systems, demonstrating how semiconductor properties enable enhanced performance through materials engineering. We contrast passive components with active photonic devices, illustrating how the semiconductor nature of these polymers facilitates novel functionalities beyond simple light guiding. The review explores emerging applications in neuromorphic photonics, quantum systems, and bio-integrated devices, where the combined electronic-optical properties of organic semiconductors create unique capabilities impossible with insulating polymers. Finally, we discuss design strategies for optimizing these distinctive properties and present perspectives on future developments. This review establishes organic semiconductors as transformative materials for advancing photonic technologies through their combined electronic-optical functionality.  
organic semiconductors; photonic devices; conjugated polymers 27 January  
for chemical modification and tuning of optical properties, make polymers increasingly relevant for next-generation photonic devices.  
Within the broader class of polymeric materials, organic semiconductors represent a particularly interesting subset due to their unique combination of optical and electronic properties. These materials, characterized by their conjugated molecular structure, exhibit strong light-matter interactions and can be engineered to display specific optical characteristics. Their semiconductor nature, arising from delocalized \(\pi\)-electron systems, enables both electronic and optical functionality, making them suitable for active photonic components [6, 7]. Furthermore, organic semiconductors often exhibit significant nonlinear optical properties, which are essential for applications in optical switching, frequency conversion, and signal processing.  
The integration of organic semiconductors as optically active polymer materials in photonic applications represents a convergence of several advantageous properties: solution processability, which enables low-cost manufacturing; structural flexibility, allowing for diverse device architectures; and tunable optoelectronic properties, providing versatility in application design. These materials have demonstrated potential in various photonic applications, ranging from conventional devices such as light-emitting diodes and photodetectors to more advanced applications including optical amplifiers, modulators, and nonlinear optical devices [2, 8, 9].  
Recent advances in molecular design and synthesis techniques have further expanded the possibilities for organic semiconductor-based photonic materials [10, 11]. The ability to precisely control molecular structure and organization has led to enhanced optical properties and improved device performance. Additionally, the development of new processing methods and device architectures has facilitated better integration of these materials into practical photonic systems.  
This review aims to provide an overview of the current state of the art in organic semiconductors as optically active polymer materials for photonic applications. We will examine the fundamental principles governing their optical properties, discuss various material systems and their characteristics, and explore emerging applications and future prospects in this rapidly evolving field.