Journal Article n-type polymer semiconductors all-polymer solar cells organic electrochemical transistors electron mobility morphology optimization narrow bandgap nonfullerene polymer solar cells organic thermoelectrics 1,3,4-oxadiazole acceptor-acceptor polymers buried interface conductivity conjugated polymer copper(I) coordination strategy cyano functionalization cyano-functionalization defect passivation dicyanobenzothiadiazole diluted organic semiconductors glucose sensors halogen functionalization high absorption coefficient high electron mobility mixed ionic-electronic conductors morphology control n-type polymers organic bioelectronics organic electrochemical transistor organic mixed ionic-electronic conductors