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There are only a few examples of nanocrystal synthesis with thallium (Tl). Here, we report the synthesis of uniform, ligand‐stabilized colloidal nanocrystals of TlBr and Tl₂AgBr₃nanocrystals with average diameter ranging between 10 and 20 nm. TlBr nanocrystals are made by hot injection of trimethylsilyl bromide (TMSBr) into solutions of oleylamine, oleic acid and octadecene with thallium (III) or thallium (I) acetate. Tl₂AgBr₃nanocrystals form when silver (I) acetate is included in the reaction. The TlBr nanocrystals have CsCl crystal structure with a direct band gap of 3.1 eV. The Tl₂AgBr₃nanocrystals have trigonal dolomite crystal structure with an indirect band gap of 3.1 eV. The TlBr nanocrystals made with thallium (III) were sufficiently uniform to assemble into face‐centered cubic (fcc) superlattices.

 

A microsecond time-scale photonic lift-off (PLO) process was used to fabricate mechanically flexible photovoltaic devices (PVs) with a total thickness of less than 20 μm. PLO is a rapid, scalable photothermal technique for processing extremely thin, mechanically flexible electronic and optoelectronic devices. PLO is also compatible with large-area devices, roll-to-roll processing, and substrates with low temperature compatibility. As a proof of concept, PVs were fabricated using CuInSe2 nanocrystal ink deposited at room temperature under ambient conditions on thin, plastic substrates heated to 100 °C. It was necessary to prevent cracking of the brittle top contact layer of indium tin oxide (ITO) during lift-off, either by using a layer of silver nanowires (AgNW) as the top contact or by infusing the ITO layer with AgNW. This approach could generally be used to improve the mechanical versatility of current collectors in a variety of ultrathin electronic and optoelectronic devices requiring a transparent conductive contact layer.