Performance improvement in inverted organic solar cells by incorporating core-shell SiO ₂ @Au plasmonic structures

Organic solar cells (OSCs) are very attractive as a clean and renewable energy technology owing to their advantages of low cost, abundant material sources, good flexibility, etc. Nevertheless, OSCs are faced with the contradictions between the optical and electrical properties. Their low absorption efficiency requires a thick active layer for efficient light harvesting, while the short carrier transport distance implies a thin active layer is necessary for efficient charge extraction. One way to solve this contradiction is to effectively enhance light absorption in the active layer without increasing the thickness. In this work, a core-shell structured plasmonic nanoparticles in the form of Au nanorod core coated with a SiO ₂ shell (in short of Au NR@SiO ₂ ) were introduced at the interface between the active and the cathode buffer layer of an inverted OSC based on PTB7:PC70BM active layer. By adjusting the concentration of the plasmonic nanoparticles of Au NRs@SiO ₂ , we optimized the optoelectronic performances of OSCs. The results indicated when we spin-coated 1 pM Au NRs@SiO ₂ on top of the buffer layer, the device performances were optimized with the short circuit current increasing significantly while the open circuit voltage bearing negligible change. Overall, the power conversion efficiency of the OSC increases from 6.52% to 7.03%, corresponding to an enhancement of 8% as compared to that of the structurally identical control cell without Au NRs@SiO ₂ . The performance improvement in inverted OSCs is mainly resulted from efficient light trapping effect of the core-shell plasmonic nanoparticles.