Integrated colloidal quantum dot devices for on-chip light sources

The rapid advancement of photonic integrated circuits (PICs) has presented a promising solution to meet future demands for faster data transmission, broader bandwidth, and lower power consumption. However, the indirect bandgap of silicon presents challenges in achieving optical gain, necessitating the integration of III-V materials through complex and costly bonding or epitaxial techniques. In this context, colloidal quantum dots (CQDs) have emerged as a viable alternative for on-chip light sources due to their unique properties, including cost-effective synthesis, high photoluminescence quantum yield, precisely tunable emission wavelengths across visible to near-infrared, and excellent solution processability. These distinct advantages position CQDs as promising components for next-generation optoelectronic devices, fueling advancements in fields such as telecommunications, sensing, and display technologies. In this review, we systematically examine the structural evolution of CQDs aiming at luminescent property enhancement and explore their integration with various photonic platforms. Key applications are discussed, focusing on waveguide-coupled CQD light-emitting diodes and lasers, metasurface-integrated CQD lasers, and cavity-coupled CQD single-photon sources. Additionally, this review presents recent efforts in promoting electrically pumped CQD lasers, highlighting the potential of CQD light sources to revolutionize on-chip photonic systems. Finally, we present prospects for further development of CQD-based on-chip light sources, emphasizing their role in the future of integrated photonics.