Nitrates/Sulphides

Cadmium Sulfide Powder has, like zinc sulfide, two crystal forms. The more stable hexagonal wurtzite structure (found in the mineral Greenockite) and the cubic zinc blende structure (found in the mineral Hawleyite). In both of these forms the cadmium and sulfur atoms are four coordinate. There is also a high pressure form with the NaCl rock salt structure. It brings to mind the sun, egg yolks, positive warm feelings. It is very much an affirmative colour, but not one that is always easy to produce. In chemistry, yellow is not unheard of – sulfur springs to mind immediately – yet a good strong yellow is rare enough to comment on, and cadmium sulfide delivers it with bells on.

The valence and conduction bands overlap, while in an insulator the gap is so big that electrons can rarely jump across it. A semiconductor like Cadmium Sulfide Powder sits in between, with a small enough gap that a relatively small input of energy is enough to get an electron into the conduction band. Expose cadmium sulfide to light and it can make use of the extra energy to make it easier for an electron to cross to the conduction layer, making cadmium sulfide an effective photoresistor. It can also be used with a doped semiconductor to produce photovoltaic cells for solar panels.

The yellow colour of cadmium sulfide reflects its other use – as a semiconductor. Cadmium Sulfide Powder is a bandgap semiconductor, meaning that its semiconducting properties are intrinsic to the compound, rather than as a result of introduced impurities in a doping process. The energy levels of electrons in a material are not continuous, but come in bands. To get from the highest energy band containing electrons, the ‘valence band’, to the conduction band where the electrons can flow to produce conductivity, means crossing a ‘band gap’. Cadmium sulfide’s yellow colour comes from the energy of the photons the compound absorbs to promote electrons across this gap.

Cadmium Sulfide Powder is a chemical compound that has the formula CdS. It is yellow in color and is a semiconductor of electricity. It exists as two different polymorphs, hexagonal greenockite and cubic hawleyite. Cadmium Sulfide is also used in the production of solar cells where it is used as a buffer layer in the manufacture of CIGS (Copper -Indium-Gallium-Selenide) solar cells. With an increasing interest and uptake of solar cells application.

Cadmium Sulfide Powder is a direct band gap semiconductor (gap 2.42 eV). The magnitude of its band gap means that it appears coloured. the conductivity increases when irradiated with light (leading to uses as a photoresistor).when combined with a p-type semiconductor it forms the core component of a photovoltaic (solar) cell and a CdS/Cu2S solar cell was one of the first efficient cells. when doped with for example Cu+ (“activator”) and Al3+ (“coactivator”) CdS luminesces under electron beam excitation (cathodoluminescence) and is used as phosphor.