Hole transport mechanism in organic/inorganic hybrid system based on in-situ grown cadmium telluride nanocrystals in poly(3-hexylthiophene)

Abstract

The present manuscript demonstrates the hole transport mechanism in an organic/inorganic hybrid system based on in-situ grown cadmium telluride (CdTe) nanocrystals in a poly(3-hexylthiophene) (P3HT) matrix. The increase of hole current in the hybrid system is correlated with the formation of a host-guest (P3HT-CdTe) charge transfer complex duly supported by photoluminescence quenching. The hole transport mechanism in P3HT is governed by a space charge limited current with temperature, carrier density, and field dependent mobility. Incorporation of CdTe nanocrystals in a polymer matrix results in enhancement in the value of trap density H b from 2.8 Â 10 18 to 5.0 Â 10 18 cm À3 and reduction in activation energies from 52 meV to 11 meV. At high trap density, trap potential wells start overlapping; this results in decrease of activation energies.

Diacetylene bridged triphenylamines as hole transport materials for solid state dye sensitized solar cells

“…The Ohmic region has been attributed to the background impurity conduction where the injected hole carrier density is smaller than the intrinsic carrier density in the samples. 30 The non Ohmic behavior at high elds has been analyzed in terms of space charge limited current (SCLC) and tted as previously reported to extract the charge mobility ( Table 3, see ESI † for more details). DATPA derivatives show charge mobility about two orders of magnitude lower than Spiro-OMeTAD.…”

“…Fig. 7a shows the characteristic current-voltage ( J-V ) curves of Table 3 Carrier mobility estimated by fitting of current-voltage curves 30 reported in Fig. 6 and conductivity Fig.…”

“…The work function of Au and ITO are close to the HOMO energy level of the HTMs as well as far below the LUMO energy level. 30 Therefore, the electron injection barrier is higher than the corresponding hole injection barrier. As a result, the transport is dominated by holes.…”

“…Charge transport in the HTMs has been investigated according to a published procedure. 30 Poly(3,4-ethylendioxythiophene)poly(styrene sulfonate) (PEDOT:PSS) was spin-coated onto indium tin oxide substrate (ITO) and dried at 140 C for 30 min in vacuum. The purpose of PEDOT:PSS layer (40 nm) was to reduce the roughness of ITO as well as to improve the work function, achieving enhanced hole-only device properties.…”

“…-V characteristics of devices experimental (symbols) and calculated (solid lines) for H-DATPA (black), Me-DATPA (red), MeS-DATPA (purple), MeO-DATPA (green) and Spiro-OMeTAD (blue) using the procedure previously reported 30. …”