A versatile solution-processed MoO₃/Au nanoparticles/MoO₃ hole contact for high performing PEDOT:PSS-free organic solar cells

Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) hole contact is widely used in organic solar cells (OSCs). In this work, we report the effort to develop a versatile solution-processed molybdenum trioxide (s-MoO₃)/Au nanoparticles (NPs)/s-MoO₃ (MAM) hole contact for application in PEDOT:PSS-free OSCs. The use of Au NPs is to improve the adhesion between the two s-MoO₃ layers in the MAM hole contact. It shows that MAM hole contact enables to enhance the charge extraction through suppression of bimolecular recombination, and reduce the leakage current by improvement of contact property. Power conversion efficiency of 7.68% was obtained for MAM-based OSCs, with a blend system of poly[[4,8-bis[(2-ethylhexyl) oxy]benzo[1,2-b: 4,5-b’] dithiophene-2,6-diyl] [3-fluoro-2-[(2-ethylhexyl) carbonyl] thieno[3,4-b]-thiophenediyl]]: [6,6]- phenyl-C70-butyric-acid-methyl-ester, which is comparable to that of the PEDOT:PSS-based cells (7.48%). It demonstrates clearly that solution-processed MAM hole contact can be readily adopted to replace the widely used acidic PEDOT:PSS hole contact for application in PEDOT:PSS-free OSCs.