Enhancing the performance of organic solar cells and polymer light emitting diodes via a novel giant polyoxomolybdate bifunctional interlayer material

The giant polyoxomolybdate [(NH4)42[ $${\text{Mo}}_{72}^{{\rm{VI}}}{\text{Mo}}_{60}^{{\rm{V}}}$$ O372(CH3COO)30(H2O)72] {Mo132} has been little used for optoelectronic device applications. In this paper we demonstrate that thin films of {Mo132} and surfactant-encapsulated {Mo132}, namely {Mo132}-tetraoctyl ammonium (TOA) can, respectively, upshift and downshift the work functions of a variety of electrode materials, including Al, Ag and ITO, by forming suitable interface dipoles. {Mo132}-TOA used as a cathode interlayer (CIL) yields a power conversion efficiency of 18% for poly[(2,6-(4,8-bis(5-(2-ethylhexyl)-4-fluorothiophen-2-yl)-benzo[1,2-b:4,5-b’]dithiophene))-alt-(5,5-(1’,3’-di-2-thienyl-5’,7’-bis(2-ethylhexyl)benzo[1’,2’-c:4’,5’-c’]dithiophene-4,8-dione))] : 2,2’-((2Z,2’Z)-((12,13-bis(2-ethylhexyl)-3,9-(2-butyloctyl)-12,13-dihydro-[1,2,5]thiadiazolo[3,4-e]thieno[2”,3’‘:4’,5’]thieno[2’,3’:4,5]pyrrolo[3,2-g]thieno[2’,3’:4,5]thieno[3,2-b]indole-2,10-diyl)bis(methanylylidene))bis(5,6-difluoro-3-oxo-2,3-dihydro-1H-indene-2,1-diylidene)) dimalononitrile (PM6 : L8-BO) based organic solar cells (OSCs) and a current efficiency of 15.24 cd/A in Super Yellow based polymer light-emitting diodes. In addition, OSCs using both {Mo132} as anode interlayer (AIL) and {Mo132}-TOA as CIL provide improved stability relative to reference devices with traditional PEDOT:PSS as AIL and poly(9,9-bis(3’-(N,N-dimethyl)-N-ethylammoinium-propyl-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene))dibromide (PFN-Br) as CIL. {Mo132} thereby serves as an effective bifunctional interlayer material to optimize organic optoelectronic device performance, enhancing power conversion and light emission efficiencies and increasing lifetime.