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Pseudohalide Perovskites
Semiconducting lead halide perovskites are a new generation of semiconductor that have remarkably good semiconducting properties, yet are based on organic cations and lead salts that cost only a few dollars per kilogram. Perovskites have the general formula ABX3, where A, B and X are ions with charges of +1, +2 and -1, respectively. The archetypal semiconducting lead halide perovskite is methylammonium lead iodide (MAPbI3), which has been researched intensively over the past decade and yielded solar cell devices with remarkably high efficiency and low cost. A significant amount of effort has gone into finding replacements for the toxic B-site Pb2+ ion, with some success. However, the highest performance in solar cells and other semiconducting devices is always observed with Pb2+. Likewise, A lot of effort has gone into exploring A-site ions, but only methylammonium, formamidinium and cesium have been widely successful.
In contrast, relatively little effort has gone into discovering new X-site ions outside of the range of the halides (I-, Br- and Cl-). One area of interest in the ECML is to discover new polyatomic anions (pseudohalides) which can form functional perovskites with semiconducting properties.
Radical Ions
Radical ion annihilation forms the basis for many important processes in organic semiconducting devices like light-emitting diodes (OLEDs), light-emitting electrochemical cells (LECs) and electrochemiluminescense. In organic solar cells, photoinduced electron transfer is presumed to lead to a pair of oppositely charged radical ions, which can be extracted to generate electricity. Recent advances in redox flow batteries have led to the development of radical ion species which are relatively stable. One of our areas of interest is exploit these stable radical ion species to improve the stability and efficiency of optoelectronic devices.
New Types of Solar Cells
The field of solar cells is constantly evolving and our group is always looking for new types of material to explore to convert sunlight into electricity more efficiently or more economically. One interesting new type of solar cell is the light emitting solar cell, which is able to convert electricity into light, or light into electricity.
Light Emitting Transistors (LETs)
Organic light emitting diodes (OLEDs) have proven to be an extremely effective application of organic semiconductors. OLEDs are able to convert electrical energy into light with efficiencies comparable to any other kind of light source. For display applications though each OLED pixel in the display must be switched on or off using a transistor. Although the organic layers in OLEDs can be deposited economically at low temperatures, an array of silicon transistors (called a backplane) is needed to make a functioning display. This need for an array of inorganic transistors negates many of the advantages of organic semiconductors. One area of interest is in organic and hybrid LETs, which integrate the switching function of a transistor with the light emitting function of an OLED in a single device.
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