Electric field in phthalocyanine/perylene heterojunction solar cells studied by electroabsorption and photocurrent measurements

The electric-field distribution in Au/Zn-phthalocyanine(ZnPc)/3,4,9,10-perylene-tetracarboxylbis-benzimidazole(PTCBI)/In/Al heterojunction solar cells is studied by electroabsorption and photocurrent measurements. In the PTCBI surface region near the PTCBI/In interface, a large anomalous electric field exists which is nearly bias independent and does not contribute to the photocurrent generation. This anomalous electric field exists only for the PTCBI-film thickness ⩾35 nm. The electric fields in the bulk of the PTCBI and ZnPc layers are responsible for the photocurrent generation. The bulk electric field in the PTCBI layer changes its sign at a forward bias, Vbias, of 0.3 V, while that in the ZnPc layer disappears for Vbias⩾0.5 V. The latter may indicate that holes are hardly trapped in the ZnPc layer.