A chlorinated low-bandgap small-molecule acceptor for organic solar cells with 14.1% efficiency and low energy loss

Kan, B (Kan, Bin)^[ 1,2 ] ; Feng, HR (Feng, Huanran)^[ 1,2 ] ; Yao, HF (Yao, Huifeng)^[ 3 ] ; Chang, MJ (Chang, Meijia)^[ 1,2 ] ; Wan, XJ (Wan, Xiangjian)^[ 1,2 ] ; Li, CX(Li, Chenxi)^[ 1,2 ] ; Hou, JH (Hou, Jianhui)^[ 3 ] ; Chen, YS (Chen, Yongsheng)^[ 1,2 ]

SCIENCE CHINA-CHEMISTRY, 2018, 61(10): 1307-1313

DOI: 10.1007/s11426-018-9334-9

 WOS:000446627600015

Abstract

A new acceptor-donor-acceptor (A-D-A) type small-molecule acceptor NCBDT-4Cl using chlorinated end groups is reported. This new-designed molecule demonstrates wide and efficient absorption ability in the range of 600-900 nm with a narrow optical bandgap of 1.40 eV. The device based on PBDB-T-SF:NCBDT-4Cl shows a power conversion efficiency (PCE) of 13.1% without any post-treatment, which represents the best result for all as-cast organic solar cells (OSCs) to date. After device optimizations, the PCE was further enhanced to over 14% with a high short-circuit current density (J (sc)) of 22.35 mA cm(-2) and a fill-factor (FF) of 74.3%. The improved performance was attributed to the more efficient photo-electron conversion process in the optimal device. To our knowledge, this outstanding efficiency of 14.1% with an energy loss as low as 0.55 eV is among the best results for all single-junction OSCs.