Electron-transporting third component modifying cathode for simplified inverted ternary blend solar cells

Bathophenanthroline (Bphen), an electron transporting material widely used in organic light-emitting diodes, was added as a third component into a mixed solution of poly(thieno[3,4- b ]-thiophene/benzodithiophene) (PTB7) and [6,6]-phenyl C 71 -butyric acid methyl ester (PC 71 BM) to fabricate simplified inverted polymer solar cells (PSCs). Bphen spontaneously migrated onto the ITO cathode during spin coating, and thereby formed a thin modifying interlayer between the cathode and the active layer. PSCs based on the ternary blend PTB7:PC 71 BM:Bphen showed a power conversion efficiency of 5.35%, higher than that of the binary blend PTB7:PC 71 BM in an inverted structure of ITO/photoactive layer/MoO 3 /Ag without an additional cathode-modifying interlayer (3.43%). The other electron transporting materials, 1,3,5-tris(2- N -phenylbenzimidazolyl)benzene (TPBI) and bathocuproine (BCP), were also confirmed to function as Bphen. This strategy simplifies the structure of inverted PSCs without significant loss in efficiency. Electron transporting materials widely used in organic light-emitting diodes, such as Bphen, BCP and TPBI, are used as a third component to serve as a cathode buffer layer for fabricating simplified inverted ternary blend polymer solar cells without an additional cathode-modifying interlayer.