MoO<sub>3</sub> Nanodots Decorated CdS Nanoribbons
for High-Performance, Homojunction Photovoltaic Devices on Flexible
Substrates
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Abstract
The p–n homojunctions are
essential components for high-efficiency optoelectronic devices. However,
the lack of p-type doping in CdS nanostructures hampers the fabrication
of efficient photovoltaic (PV) devices from homojunctions. Here we report a facile solution-processed
method to achieve efficient p-type doping in CdS nanoribbons (NRs)
via a surface charge transfer mechanism by using spin-coated MoO<sub>3</sub> nanodots (NDs). The NDs-decorated CdS NRs exhibited a hole
concentration as high as 8.5 × 10<sup>19</sup> cm<sup>–3</sup>, with the p-type conductivity tunable in a wide range of 7 orders
of magnitude. The surface charge transfer mechanism was characterized
in detail by X-ray photoelectron spectroscopy, Kelvin probe force
microscopy, and first-principle calculations. CdS NR-homojunction
PV devices fabricated on a flexible substrate exhibited a power conversion
efficiency of 5.48%, which was significantly better than most of the
CdS nanostructure-based heterojunction devices, presumably due to
minimal junction defects. Devices made by connecting cells in series
or in parallel exhibited enhanced power output, demonstrating the
promising potential of the homojunction PV devices for device integration.
Given the high efficiency of the surface charge transfer doping and
the solution-processing capability of the method, our work opens up
unique opportunities for high-performance, low-cost optoelectronic
devices based on CdS homojunctions