Dimeric Phenazinothiadiazole Acceptors in Bulk Heterojunction Solar Cells
Two covalently linked triisopropylsilyl-ethynylated phenazinothiadiazoles were prepared through condensation of a spirocyclic and a bicyclic tetraketone with a 5,6-diaminobenzothiadiazole. The spirobisindene- and the ethanoanthracene-based linkers render the electron acceptors amorphous in thin films. The optoelectronic properties of the non-conjugated dimers are indistinguishable from that of the crystalline monomer. Bulk heterojunction solar cells were prepared with power conversion efficiencies peaking at 1.6%. The choice of linker neither influenced optical and electrochemical properties nor device performance.