Semiconductor properties of polyacetylene p-(CH)x : n-CdS heterojunctions

Abstract

Trans:(CH)_x:n‐CdS heterojunctions have been fabricated and used to study the properties of undoped trans‐polyacetylene. The I‐V data show rectifying behavior characteristic of a p‐n junction diode, thus confirming that as‐grown polyacetylene is p type. From C‐V characteristics we infer a residual acceptor concentration in as‐grown films of p‐(CH)_x of N_A?2×10¹⁸ cm⁻³. Depletion has been studied in the polymer by using CdS of different doping concentrations. Detailed studies of the photovoltaic response at energies below E_g for (CH)_x imply the existence of a meta‐stable deep trap in the polymer with energy near the center of the gap. The threshold energy for pumping into this level provides an independent measurement of the energy gap, E_g=1.45 eV.