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New technique offers spray-on power

December 5, 2014

TORONTO, ON — Pret­ty soon, pow­er­ing your tablet could be as sim­ple as wrap­ping it in cling wrap.

That’s Illan Kramer’s hope. Kramer and col­leagues have just invent­ed a new way to spray solar cells onto flex­i­ble sur­faces using minis­cule light-sen­si­tive mate­ri­als known as col­loidal quan­tum dots (CQDs)—a major step toward mak­ing spray-on solar cells easy and cheap to man­u­fac­ture.

“My dream is that one day you’ll have two tech­ni­cians with Ghost­busters back­packs come to your house and spray your roof,” says Kramer, a post-doc­tor­al fel­low with The Edward S. Rogers Sr. Depart­ment of Elec­tri­cal & Com­put­er Engi­neer­ing at the Uni­ver­si­ty of Toron­to and IBM Canada’s Research and Devel­op­ment Cen­tre.

Solar-sen­si­tive CQDs print­ed onto a flex­i­ble film could be used to coat all kinds of weird­ly shaped sur­faces, from patio fur­ni­ture to an airplane’s wing. A sur­face the size of your car’s roof wrapped with CQD-coat­ed film would pro­duce enough ener­gy to pow­er three 100-Watt light bulbs—or 24 com­pact flu­o­res­cents.

He calls his sys­tem sprayLD, a play on the man­u­fac­tur­ing process called ALD, short for atom­ic lay­er depo­si­tion, in which mate­ri­als are laid down on a sur­face one atom-thick­ness at a time.

Until now, it was only pos­si­ble to incor­po­rate light-sen­si­tive CQDs onto sur­faces through batch processing—an inef­fi­cient, slow and expen­sive assem­bly-line approach to chem­i­cal coat­ing. SprayLD blasts a liq­uid con­tain­ing CQDs direct­ly onto flex­i­ble sur­faces, such as film or plas­tic, like print­ing a news­pa­per by apply­ing ink onto a roll of paper. This roll-to-roll coat­ing method makes incor­po­rat­ing solar cells into exist­ing man­u­fac­tur­ing process­es much sim­pler. In two recent papers in the jour­nals Advanced Mate­ri­als and Applied Physics Let­ters, Kramer showed that the sprayLD method can be used on flex­i­ble mate­ri­als with­out any major loss in solar-cell effi­cien­cy.

Kramer built his sprayLD device using parts that are read­i­ly avail­able and rather affordable—he sourced a spray noz­zle used in steel mills to cool steel with a fine mist of water, and a few reg­u­lar air brush­es from an art store.

“This is some­thing you can build in a Junk­yard Wars fash­ion, which is basi­cal­ly how we did it,” says Kramer. “We think of this as a no-com­pro­mise solu­tion for shift­ing from batch pro­cess­ing to roll-to-roll.”

“As quan­tum dot solar tech­nol­o­gy advances rapid­ly in per­for­mance, it’s impor­tant to deter­mine how to scale them and make this new class of solar tech­nolo­gies man­u­fac­turable,” said Pro­fes­sor Ted Sar­gent, vice dean, research in the Fac­ul­ty of Applied Sci­ence & Engi­neer­ing at Uni­ver­si­ty of Toron­to and Kramer’s super­vi­sor. “We were thrilled when this attrac­tive­ly man­u­fac­turable spray-coat­ing process also led to supe­ri­or per­for­mance devices show­ing improved con­trol and puri­ty.”

In a third paper in the jour­nal ACS Nano, Kramer and his col­leagues used IBM’s Blue­GeneQ super­com­put­er to mod­el how and why the sprayed CQDs per­form just as well as—and in some cas­es bet­ter than—their batch-processed coun­ter­parts. This work was sup­port­ed by the IBM Cana­da Research and Devel­op­ment Cen­tre, and by King Abdul­lah Uni­ver­si­ty of Sci­ence and Tech­nol­o­gy.

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Watch video: http://youtu.be/Q7DZzufHy1o

More infor­ma­tion:

Mar­it Mitchell
Senior Com­mu­ni­ca­tions Offi­cer, The Edward S. Rogers Sr. Depart­ment of Elec­tri­cal & Com­put­er Engi­neer­ing
416–978-7997; marit.mitchell@utoronto.ca