NiO x Nanoparticles Hole-Transporting Layer Regulated by Ionic Radius-Controlled Doping and Reductive Agent for Organic Solar Cells with Efficiency of 19.18.

Nickel oxide (NiO x ) has garnered considerable attention as a prospective hole-transporting layer (HTL) in organic solar cells (OSCs), offering a potential solution to the stability challenges posed by traditional HTL, PEDOT:PSS, arising from acidity and hygroscopicity. Nevertheless, lower work function (WF) of NiO x relative to donor polymers reduces charge injection efficiency in OSCs. Herein, we tailor NiO x nanoparticles through rare earth doping to optimize WF and explore the impact of ionic radius on their electronic properties. Lanthanum (La 3+ ) and yttrium (Y 3+ ) ions, with larger ionic radii, are effectively doped at 1% and 3%, respectively, while scandium (Sc 3+ ), with a smaller ion radius, allows enhanced 5% doping. Higher doping ratios significantly enhance WF of NiO x . A 5% Sc 3+ doping raises WF to 4.99 eV from 4.77 eV for neat NiO x while maintaining high conductivity. Consequently, using 5% Sc-doped NiO x as HTL improves power conversion efficiency (PCE) of OSCs to 17.13%, surpassing the 15.64% with the neat NiO x . Further enhancement to 18.42% has been achieved by introducing the reductant catechol, outperforming the PEDOT:PSS-based devices. Additionally, when employed in a ternary blend system (D18: N3: F-BTA3), an impressive PCE of 19.18 % has been realized, top-performing among reported OSCs utilizing solution-processed inorganic nanoparticles. This article is protected by copyright. All rights reserved.