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Organic–Inorganic Charge Transfer Complex with Charge Modulation after Electrical Pre-biasing
journal contribution
posted on 2020-08-07, 10:14 authored by Dong Shen, Chunqing Ma, Tsz-Wai Ng, Hrisheekesh Thachoth Chandran, Ming-Fai Lo, Chun-Sing LeeSeveral breakthroughs
in organic optoelectronic devices with new
applications and performance improvement have been made recently by
exploiting novel properties of charge transfer complexes (CTCs). In
this work, a CTC film formed by coevaporating molybdenum(VI) oxide
and pentacene (MoO3:pentacene) shows a strong dipole of
2.4 eV with direction controllability via pre-biasing with an external
voltage. While CTCs are most widely known for their much red-shifted
energy gaps, there is so far no report on their controllable dipoles.
By controlling this dipole with an electrical pre-bias in a MoO3:pentacene CTC based device, current changes over 2 orders
of magnitude can be achieved. Kelvin probe force microscopy further
confirms that surface potential of the MoO3:pentacene film
can be modulated by an external electric field. It is shown for the
first time that a dipole of controllable direction can be set up inside
a CTC layer by pre-biasing. This concept is further tested by incorporating
the CTC layer in organic photovoltaic (OPV) devices. It was demonstrated
that by pre-biasing the OPV devices in different directions, their
open circuit voltages (Voc) can be significantly
tuned via the built-in potentials.