Nonfullerene Polymer Solar Cell with Large Active Area of 216 cm² 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 C₇₁-butyric acid methyl ester (PC₇₁BM). 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 cm², the best power conversion efficiency is 9.8% with the LiF interfacial layer. For a large active area of 216 cm², 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.