Observation of Electrical Switching, Reverse Rectification and Hysteresis in Nanostructured Organic–Organic Heterojunction

Abstract

Nanostructured organic-organic (O-O) heterojunction was fabricated by using the thin films of a hole transporting material, copper phthalocyanine (CuPc) and an electron transporting material, copper hexadecafluoro-phthalocyanine (F16CuPc). The nanostructured thin films were characterized by optical absorption spectra, FESEM, AFM, X-ray diffraction, etc. Grain size of CuPc and F16CuPc on the substrate surface was different. XRD analysis shows that the crystallinity of the double layer films/heterojunction decreases as compared to the single layer film. The heterojunction sandwich structure ITO/F16CuPc/CuPc/Al, in the present study has shown a good diode like current-voltage (I-V) characteristics with reverse rectifying characteristics. In addition, electrical switching and hysteresis phenomena have also been observed in both sides of the voltage polarities. Interestingly, the single layer sandwich structure of the type ITO/CuPc/Al and ITO/F16CuPc/Al did not show any noticeable electrical switching and hysteresis in I-V characteristics as compared to double layer heterostructure. The reverse rectification has been explained on the basis of band bending due to the accumulation of charge carriers near the junction and the electrical switching has been explained considering the charge carriers trapping and detrapping at the O-O interface.