Researchers from Duke University/Pratt School of Engineering (United States) have developed a new method for producing hybrid thin-film materials that would be difficult or impossible to realize using conventional methods. This new method can open the door to new generations of solar cells, LEDs and photo detectors.
Perovskites are materials that – with the correct combination of elements – have a crystal structure that makes them eminently suitable for applications that involve light. Because of their light-absorbing and energy-carrying characteristics they are extremely interesting for the development of new types of solar cells.
Methylammonium lead iodide (MAPbI3), a compound of an organic and inorganic element, is the most-used perovskite for solar cells; this materials can convert light into electrical energy just as well as the best commercially available solar panels, but with a much smaller amount of material: a slice that is 100 times thinner than a typical silicon solar cell will suffice.
Methylammonium lead iodide is one of the few perovskites that can be produced using 'normal' production techniques. Other types, however, require new techniques.
Professors Adrienne Stiff-Roberts and David Mitzi have developed a technique that has been given the name RIR-MAPLE: Resonant InfraRed Matrix-Assisted Pulsed Laser Evaporation. With this, a solvent that contains the building blocks of the desired perovskite is frozen into a block, after which this block is blasted with laser pulses in a vacuum chamber.
When a small part of the frozen solvent is evaporated by the laser, the vapor moves up and condenses on the bottom of an object that was previously suspended above the solution. Once enough material have been deposited, the object is heated to cause the condensed molecules to crystallize.
Because organic materials such as methylammonium are extremely fragile, the laser frequency is tuned to the molecular bonds of the solvent. This then absorbs most of the laser energy so that the delicate organic materials are deposited intact on the object.