Solution processed CuSCN/perylene hole extraction layer for highly efficient and stable organic solar cells

In this work, we report a solution processed hole extraction layer (HEL) for highly efficient organic solar cells (OSCs), which is formed by CuSCN and perylene . It shows that the introduction of perylene helps to polish the interface between HEL and active layers, leading to efficient charge transport and collection, diminished recombination loss , and thereby improving the photovoltaic performance . In poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2- b ; 4,5- b ′]dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4- b ]thiophene-)-2-carboxylate-2-6-diyl)]:[6,6]-phenyl C 71 -butyric acid methyl ester (PTB7-Th:PC 71 BM) based OSCs, over 9% enhancement of power conversion efficiency (PCE) is obtained in the cells using bilayer CuSCN/perylene as HEL compared with that of the reference cell using pure CuSCN as HEL. The advantage of bilayer CuSCN/perylene HEL is also confirmed in nonfullerene system. An improved PCE is also obtained after application of perylene in nonfullerene system based cell. Furthermore, superior air stability has been observed in CuSCN and CuSCN/perylene HEL based cells. The use of a bilayer CuSCN/perylene HEL proves a potential approach to obtain efficient and stable OSCs.