Black Phosphorus Uses and Applications
Due to the unique properties, exfoliated monolayer and few-layer black phosphorus have potential for a wide range of applications in electronics and optoelectronics. Applications that have been suggested (or are currently being investigated) include photodetectors, supercapacitors, superconductors, and memory devices.
Black phosphorus powder can also be used to prepare black phosphorus quantum dots (BPQDs). The properties of BPQDs make them well suited for the development of thermoelectric devices, sensors, LEDs, OPVs, and energy storage systems.
What is Black Phosphorus Used For?
Photovoltaics and Solar Cells
The photovoltaic effect has been observed in few-layer black phosphorus (Buscema et al, 2014) making this material useful in solar technology.
With thicker samples having a bandgap smaller than that of silicon, it could be used to harvest the NIR-IR region of the solar spectrum that silicon cannot access. While the observed external quantum efficiencies observed so far are small (<1%), it has been predicted that a modified phosphorene structure could reach efficiencies of 20% (Hu et al, 2016).
Photodetectors in Communication Networks
Phosphorene has a direct bandgap that is tunable (between 0.3 eV to 1.88 eV) by changing the number of stacked layers. This makes it optically active in the red to NIR spectrum and has allowed the fabrication of visible to NIR photodetectors (Youngblood et al., 2015). This region of the spectrum is important for optical fibre networks and suggests that phosphorene could play a role in future communication networks.
Gas Sensors
Phosphorene is an interesting material for chemical sensing due to its large surface-to-volume ratio and the presence of a lone electron pair on each atom. An NO2 sensor has been demonstrated with a sensitivity of 20 parts per billion in air (Cui et al., 2015). While a theoretical study has suggested that single molecule sensing may be possible with such sensors (Kistanov et al., 2016).
Field-Effect Transistors for Electronic Devices
Field-effect transistors (FETs) are the most studied of phosphorene’s potential applications, with many theoretical and experimental studies carried out over the last 5 years. The attractive FET characteristics of relatively high on/off ratio and good charge carrier mobility, along with a high conductivity, should ensure fast switching with high efficiency and error-free logic.
Flexible Memory Devices
Black phosphorus quantum dots have the potential to be used as the active layer in flexible memory devices. They have exhibited a non-volatile, re-writable memory effect with high on/off current ratios (more than 6.0 × 104).
Energy Storage and Battery Electrodes
Phosphorene combines a significant, reversible charge-storage capacity with a small volume change and good electrical conductivity. This combination of properties makes it good candidate for energy storage applications.
Phosphorene has therefore been proposed as an anode material for Li-ion batteries, with lithium diffusion expected to be orders of magnitude faster than in other 2D materials (Li et al.,2015). Advanced structural engineering, incorporation into heterostructures with other 2D materials, and the addition of defect states is expected to improve lithium diffusion rates and binding energies.
Few-layer black phosphorus may also find application in future sodium ion batteries which are the expected replacement for lithium ion (Kulish et al., 2015). In contrast to current graphite anodes, the large interlayer spacing of phosphorene allows for the diffusion of large sodium ions.
Black Phosphorus
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Black Phosphorus Structure
Black phosphorus has gained attention for its distinct structural properties when reduced to two-dimensional layers known as phosphorene.
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What is a Photodetector?
A photodetector is a device that can detect light, or more specifically photons. They are classed as optoelectronic devices like photovoltaic devices. This is because they produce an electronic signal which is proportional to the incident optical input.
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- Buscema, M. et al. (2014). Photovoltaic effect in few-layer black phosphorus PN junctions defined by local electrostatic gating. Nature Communications, 5.
- Buscema, M. et al. (2015). Fast and broadband photoresponse of few-layer black phosphorus field-effect transistors. Nano Lett., 14(6).
- Cui, S. et al. (2015). Ultrahigh sensitivity and layer-dependent sensing performance of phosphorene-based gas sensors. Nature Communications, 6.