“…However, there may be heterojunction effect, where the Fermi levels alignment causes the band bending and the built-in field that hinders or facilitates the injection of the carriers from the active layer to the charge trapping layer. The band bending and the built-in field caused by the energy level alignment has also been proved in organic heterojunctions, such as in Copper (II) 1,2,3,4,8,9,10,11,15,16,17,18,22,23,24,25-hexadecafluoro-29H,31Hphthalocyanine (F 16 CuPc)/ Copper (II) Phthalocyanine (CuPc) heterojunction [20], in Zinc Phthalocyanine (ZnPc)/ fullerene (C 60 ) heterojunction [21]. The band bending due to the Fermi-level alignment causes space charge regions that the charge accumulates at the heterojunction interface to form accumulation-type heterojunction, or charge depletes at the heterojunction interface to form depletion-type heterojunction.…”