Controlling Doping Concentration of Metal Nanoparticles for Enhanced Performance in NFA-Based Organic Solar Cell

Nanostructured metals have been employed as an important ingredient to enhance performance in photonic devices. It has attracted special interest in thin-film organic solar cells (TFOSCs) as a mechanism to improve photon capture using thin solar absorber. Potassium sulphide doped with silver (K₂S/Ag) was synthesized with the view to have core shell like structures nanoparticle (NP). The particles were then incorporated into solar absorber layer of TFOSCs at different concentrations. Nonfullerene acceptor (NFA)-based solar cells were fabricated, in an inverted device structure, using an active layer composed of donor polymer poly-(4,8-bis(5-(2-ethylhexyl) thiophene-2-yl)benzo[1,2-b; 4,5-b′]-dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluoro-thieno [3,4,b]-thiophene-)-2-carboxylate-2-6-diyl) (PTB7-Th), and nonfullerene (NFA), 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(5-hexyl-thienyl)-dithieno[2,3-d:2′,3′-d′]-s-indaceno[1,2-b:5,6-b′]dithiophene (ITIC-Th). This study reveals the importance of the optimal percolation threshold for efficient charge transport in NFA-based TFOSC. The highest performance was achieved at 1% concentration with a PCE as high as 10.51%, $J_{\mathrm{sc}}$ of 23.74 mA/cm², and FF of 58.86% compared to the reference cell. Such results indicate that the measured electrical and optical properties of the K₂S/Ag metal NPs doped polymer films demonstrated augmented characteristics for photon energy harvesting. The study highlights the importance controlling concentrations as it is evident from device performances.