Nonfullerene Polymer Solar Cell with Large Active Area of 216 cm 2 and High Power Conversion Efficiency of 7.7%

A polymer solar cell involving a nonfullerene acceptor is made by blade coating. In the ternary bulk‐heterojunction layer, the donor is poly[(2,6‐(4,8‐bis(5‐(2‐ethylhexyl)thiophen‐2‐yl)benzo[1,2‐b:4,5‐b’]dithiophene))‐co‐(1,3‐di(5‐thiophene‐2‐yl)‐ 5,7‐bis(2‐ethylhexyl)benzo[1,2‐c:4,5‐c’]dithiophene‐4,8‐dione)] (PBDB‐T) and the acceptor is a mixture of 3,9‐bis(2‐methylene‐(3‐(1,1‐dicyanomethylene)‐indanone))‐5,5,11,11‐tetrakis(4‐hexylphenyl)‐dithieno[2,3‐d:2’,3’‐d’]‐s‐indaceno[1,2‐b:5,6‐b’]dithiophene) (ITIC) and [6,6]‐phenyl C 71 ‐butyric acid methyl ester (PC 71 BM). The device structure is an indium tin oxide (ITO)‐coated glass substrate/PEDOT:PSS/ternary active layer/interfacial layer/Al. For a small active area of 0.04 cm 2 , the best power conversion efficiency is 9.8% with the LiF interfacial layer. For a large active area of 216 cm 2 , the best efficiency is 7.7% with the ZrOx interfacial layer. After annealing at 85 °C for 30 days, the large‐area device keeps 75% of the initial efficiency. The efficiency of 4.9% is achieved for a large‐area semi‐transparent device.