Combinatorial study of exciplex formation at the interface between two wide band gap organic semiconductors

Combinatorial screening of exciplex formation in blends of 4,4′,4″-tris[2-naphthyl (phenyl)-amino] triphenylamine (2-TNATA), and 2,2′,7,7′-tetrakis(2,2′-diphenylvinyl) spiro-9,9′-bifluorene (spiro-DPVBi) is described. The blended layer was incorporated in ITO/ [2-TNATA]/[1:1 2-TNATA:spiro-DPVBi]/[N, N′ - diphenyl - N, N′ - bis (1-naphthylphenyl) - 1,1′ - bi-phenyl - 4,4′-diamine (NPB)]/[spiro-DPVBi]/[tris(8-hydroxy quinoline) Al]/CsF/Al organic light-emitting devices; the thickness of the blend and NPB layers were varied systematically. The electroluminescence quantum yield decreased as the blended layer thickness increased. The NPB spacer layer reduced the exciplex formation; an 8-nm-thick layer completely suppressed it.