Optical tweezers are a powerful technique that uses a highly focused laser beam to trap and manipulate microscopic particles without physical contact. This presentation discusses the fundamental principles of optical trapping, including photon momentum, gradient and scattering forces, tight focusing, and the Rayleigh and geometrical-optics regimes. The concepts of optical potential and trap stiffness are also introduced to explain how optical forces are used for microscopic manipulation and force measurements. The pioneering work of Arthur Ashkin and its connection to the 2018 Nobel Prize in Physics are highlighted. The presentation also discusses biological applications, including cell manipulation and single-molecule studies.

Perovskite solar cells have emerged as a promising next-generation photovoltaic technology, attracting significant research interest due to their remarkable efficiency, strong light absorption, tunable bandgap, and potential for low-cost fabrication. This seminar will explore the fundamental principles of perovskite solar cells, including their crystal structure, device architecture, fabrication methods, and optoelectronic properties. Attention will be given to recent efficiency advancements and major challenges, including environmental instability, lead toxicity, and manufacturing scalability. The seminar will also highlight emerging stability improvement strategies and perovskite–silicon tandem technology, offering insights into the prospects of efficient, durable, and commercially viable solar cells.