Hybrid Phototransistors Based on Bulk Heterojunction Films of Poly(3-hexylthiophene) and Zinc Oxide Nanoparticle

Abstract

Hybrid phototransistors (HPTRs) were fabricated on glass substrates using organic/inorganic hybrid bulk heterojunction films of p-type poly­(3-hexylthiophene) (P3HT) and n-type zinc oxide nanoparticles (ZnO_<i>NP</i>). The content of ZnO_<i>NP</i> was varied up to 50 wt % in order to understand the composition effect of ZnO_<i>NP</i> on the performance of HPTRs. The morphology and nanostructure of the P3HT:ZnO_<i>NP</i> films was examined by employing high resolution electron microscopes and synchrotron radiation grazing angle X-ray diffraction system. The incident light intensity (<i>P</i>_IN) was varied up to 43.6 μW/cm², whereas three major wavelengths (525 nm, 555 nm, 605 nm) corresponded to the optical absorption of P3HT were applied. Results showed that the present HPTRs showed typical p-type transistor performance even though the n-type ZnO_<i>NP</i> content increased up to 50 wt %. The highest transistor performance was obtained at 50 wt %, whereas the lowest performance was measured at 23 wt % because of the immature bulk heterojunction morphology. The drain current (<i>I</i>_D) was proportionally increased with <i>P</i>_IN due to the photocurrent generation in addition to the field-effect current. The highest apparent and corrected responsivities (<i>R</i>_A = 4.7 A/W and <i>R</i>_C = 2.07 A/W) were achieved for the HPTR with the P3HT:ZnO_<i>NP</i> film (50 wt % ZnO_<i>NP</i>) at <i>P</i>_IN = 0.27 μW/cm² (555 nm)