Design and synthesis of low band gap non-fullerene acceptors for organic solar cells with impressively high Jsc over 21 mA cm-2

Three low bandgap non-fullerene acceptors based on thieno[3,2-b] thiophene fused core with different ending groups, named TTIC-M, TTIC, TTIC-F were designed and synthesized. Using a wide bandgap polymer PBDB-T as donor to form a complementary absorption in the range of 300-900 nm, high efficencies of 9.97%, 10.87% and 9.51% were achieved for TTIC-M, TTIC and TTFC-F based photovoltaic devices with impressively high short circuit current over 21 mA cm(-2).