“Solid state charge trapping”: Examples of polymer systems showing memory effect

The paper reports on a characteristic property of electroactive materials bearing an electron-rich and an electron-poor moiety, known as charge trapping. As examples of materials that exhibit this phenomenon, films of poly(4,4″-dipentoxy-4′-(2,2′-dicyano)ethenyl-2,2′:5′,2″-terthiophene), poly(2,3-dihexylthieno[3,4-b]pyrazine) and a blend between a fulleropyrrolidine derivative and poly(3-hexylthiophene) were investigated by cyclic voltammetry, spectroelectrochemistry and electrochemical quartz crystal microbalance. In the cyclic voltammetry, the reduction processes show the reverse oxidation potential about 1 V higher than the expected value, indicating a strong stabilization of the corresponding anion species. The mechanism leading to the stabilisation of the anions is discussed and the results indicate that the investigated materials exhibit a remarkable and quite stable memory effect.