TECHNOLOGY FOCUS - POLYMERS - Preferred Materials: (B) contains direct Si-Si or Ge-Ge bonds and/or one or more partial structures of formula (I) A-Y.A = Si, Ge, Sn or Pb;Y = 2-40C aromatic or hetero-aromatic groups substituted with one or more Groups R4, vinyl groups -CR4=CR4- or -CR4=C(R4)2, acetylene group -Ctriple bondC- or -Ctriple bondCR4 or a combination of 2-5 groups and Y is a mono or divalent group;R4 = H, F, Cl, Br, I, CN, OH, NO2, branched, straight chain or cyclic alkyl, alkoxy or thioalkoxy of 1-22C (and one or non-neighbouring C atoms can be replaced by -R5C=CR5-, -Ctriple bondC-, Si(R5)2, Ge(R5)2, Sn(R5)2, -NR5-, -O-, -S-, -COO-, -OCOO- and where one or more H atoms can be replaced by F, Cl, Br, I, CN, OH or NO2) or aryl, heteroaryl or aryloxy group of 1-40C substituted with one or more groups R5 or OH, N(R5), B(R5)2 or Si(R5)3;R5 = H or 1-20C aliphatic or aromatic group.Preferably, (B) are of formulae (II)-(V)R1-R3 = H, F, CN, N(R4)2, branched, straight chain or cyclic alkyl, alkoxy or thioalkoxy of 1-40C optionally substituted with group R4 (and where one or more non-neighbouring CH2 groups can be replaced by -R5C=CR5-, -Ctriple bondC-, Si(R5)2, Ge(R5)2, Sn(R5)2, -NR5-, -O-, -S-, C=O, C=S, C=Se, C=NR5 or CONR5) or aryloxy or hetroaryloxy with 2-40C aromatic C atoms and where one or more H atoms can be replaced with F, Cl, Br, I, CN, OH or NO2 or substituted with one or more groups R4 or a combination of 2-5 such groups and where 2 or more groups R1-R3 form other mono or polycyclic aliphatic or aromatic rings; andn = 1-4.The mixtures comprise: (1) (a) 5-99.9 weight% of a polymer containing 1-100 mol% of one or more units of formulae (I) or (II)-(IV); and (b) 0.1-95 weight % of one or more triplet emitters; (2) (a) 0.5-99 weight% of a polyer containig 0.1-100 mole% of one or more covalently bonded triplet emitters; and (b) 1-99.5 weight% of compounds of formula (I) or (V) forming glassy layers at room temperature; and (3) (a) 0.5-98.5 weight% of a polymer, (b) 1-99 weight% of compounds of formula (I) or (V) forming glassy layers at room temperature and (c) 0.1-95 weight5 of one or more triplet emitters.