Current Conduction in Poly(3-Hexylthiophene) and in Poly(3- Hexylthiophene) doped [6,6]-Phenyl C61-Butyric Acid Methylester Composite Thin Film Devices

Abstract

Transport properties of poly(3-hexylthiophene) (P3HT), and of its blend with [6,6]-phenyl C61-butyric acid methylester (PCBM), were studied by analysing temperature dependent current-voltage characteristics of spin cast thin films sandwiched between aluminium electrodes in a metal-insulatormetal (MIM) configuration. It was found that in Al/P3HT/Al devices, the current is limited by space charge that accumulates near the hole injecting electrode due to the poor bulk transport properties of P3HT. At low temperatures and high applied electric fields the current density obeys a power law of the form J ∼ V m , characteristic of space charge limited current (SCLC) in the presence of exponentially distributed traps within the band gap. These traps are filled by charge that is injected by quantum mechanical tunnelling, which is adequately described by the Fowler-Nordheim (FN) theory. By calculating the majority charge carrier mobility in Al/P3HT/Al and Al/P3HT:PCBM/Al devices from the Ohmic, SCLC, and FN tunnelling fits at different temperatures, we have obtained that the charge carrier mobility in P3HT is two orders smaller than the electron mobility in the P3HT:PCBM blend at room temperature, but comparable at low temperatures. This information is important in determining the origin of open circuit voltage and short circuit current limit in solar cells that employ this blend as the active layer.

A Purely Electronic Analog Memristive Device Based on a Squaraine Nanowire Mesh

“…This TE current may be represented as the sum of Ohmic current and trap-free SCLC, i.e., I TE = I Ohm + I TF‑SCLC . Further, under these circumstances, both TE and FN carrier injection/extraction mechanisms are expected so the total current response can be expressed as I = I TE + I FN . Also, the TE current is expected to manifest as a curve of positive slope in a FN plot, and consistent with this, such a behavior was apparent in the low and intermediate bias regions in the FN plot (see Figure i).…”

On the Donor: Acceptor Features for Poly(3-hexylthiophene): TiO2 Quantum Dots Hybrid Materials Obtained via Water Vapor Flow Assisted Sol-Gel Growth

“…The larger resistance process related to the dependence of the interface-depleted region resistance (R d ) on the applied DC voltage can be shown by the slope (− m ) in the log(R d ) vs. log(V DC ) plots. The m values showed m ~1.2, 1.1 and 0.8 values for ×30, ×50 and ×70, respectively, indicating that the charge carriers exhibit a near ohmic behavior typical of semiconductor material where carriers are generated thermally by the promotion of electrons from the valence band to the conduction band [ 54 ]. In our case, the promotion of carriers can be also favored by the presence of donor–acceptor interactions in P3HT:TiO 2 nanocomposites, as we will discuss later in the manuscript.…”

Analysis of perovskite based Schottky photodiode

“…This process removes the charges from the space charge region, which enable the further injection of carriers from the electrode, leading to the increase in the carrier density, which results in the rapid change in current with applied voltage. Thus, the current is directed by the trap controlled space charge limited conduction (TCLC) process [12].…”