Naphtho[1,2-c:5,6-c′]bis([1,2,3]thiadiazole) enables the design of efficient halogen-free polymer donors and fabrication of organic solar cells with >19% efficiency

Fusion and isomerization strategies are used to develop an electron-withdrawing motif naphtho[1,2- d :5,6- d ′]bis([1,2,3]thiadiazole) (iNT) and a halogen-free polymer donor achieving an efficiency of 19.1%.