Annealed silver-islands for enhanced optical absorption in organic solar cell

• RF Sputtering can be used to produce Ag NPs at low power.
• Annealing enhances size, shape reconstruction as well as inter-particle separation.
• Annealing in Argon ambient is more suitable than in air.
• Ag NPs annealed at 250 °C enhances device absorption and PCE by up to 24%.

Silver nano-islands are explored for enhancing optical absorption and photo-conversion efficiency in organic solar cells (OSCs) based on the surface plasmon resonance effect under diverse annealing conditions. Ag nano-islands have been deposited by RF magnetron sputtering at 15 W for 10 s and subsequently annealed between 100 °C–250 °C in air and Argon ambient. The optical properties of the reconstructed Ag islands demonstrate an increase and a blue shift in the absorption bands with increasing annealing temperature. This is the localized surface plasmon effect due to the Ag islands of diverse sizes, shapes and coverages. The increase in optical absorption with temperature is attributed to changes in island shape and density as collaborated by atomic force microscopy and TEM.As a proof of concept, an organic solar cell was characterized for current–voltage (I–V) measurements under dark and under solar simulated white light. Incorporation of annealed Ag islands has yielded an efficiency increment of between 4–24%.