The research focuses on enhancing the efficiency of monocrystalline silicon (mono-Si) solar cells through the integration of multi-walled carbon nanotubes (MWCNTs) and encapsulated selenium (Se) within the N-type silicon layer. The goal is to tackle the high CO2 emissions from cities, exacerbated by fossil fuel usage in industrial and transportation sectors. MWCNTs exhibit metallic conductivity with a minimal band gap of 0.1-0.3 V, outperforming single-walled carbon nanotubes (SWCNTs) due to their overlapping electronic states, making them more efficient in conducting electrons. By incorporating MWCNTs into the emitter layer of mono-Si, which collects photogenerated electrons, resistance is reduced, leading to enhanced efficiency. MWCNTs also address surface recombination by minimizing electron-hole recombination losses, acting as bridges for charge carriers, and providing alternative pathways for improved energy collection. Moreover, MWCNTs boost photon utilization, aiding in light absorption and scattering, thus increasing the generation of charge carriers. Typical silicon solar cells suffer from overheating, which degrades their performance; however, the stability of MWCNTs under temperature variations prevents significant degradation, potentially improving efficiency in hot climates. To further enhance performance, Se is encapsulated using atomic layer deposition (ALD) with Al₂O₃ to prevent oxidation, a vital process for modern thin film deposition techniques. Integrating these materials promises to deliver solar cells with enhanced efficiency and stability across diverse environmental conditions, ultimately contributing to mitigation efforts against urban CO2 emissions. This innovative approach highlights the importance of advanced materials in modern photovoltaic technologies.