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Monday, 04/20/2015 7:06:24 PM

Monday, April 20, 2015 7:06:24 PM

Post# of 104401
Whitepaper excerpts on PV from 2015 MIT Bulovic group:
Title: Pathways for solar photovoltaics http://pubs.rsc.org/en/content/articlelanding/2015/ee/c4ee04073b/unauth#!divAbstract
Colloidal quantum dot photovoltaics (QDPV) use solution-processed nanocrystals, also known as quantum dots (QDs), to absorb light.[93–98] The ability to tune the bandgap of colloidal metal chalcogenide nanocrystals (primarily PbS) by changing their size allows e?cient harvesting of near-infrared photons,as well as the potential for multijunction cells using a single material system.99,100 QDPV technologies are improving consistently, with a record certified cell efficiency of 9.2%,[27] and they offer simple room-temperature fabrication and air-stable operation.[101] Key challenges include incomplete understanding of QD surface chemistry102–105 and low open-circuit voltages that may be limited fundamentally by mid-gap states or inherent disorder in QD. [106,107]
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...to provide a sense of scale. To supply 100% of 2050 global electricity demand with CdTePV, we need similar amounts of cadmium and tellurium:737 000 metric tons and 786 000 metric tons, respectively. Both elements thus appear at roughly the same position along the horizontal axis. But current annual cadmium production(21 800 t per year) exceeds tellurium production (525 t per year)by two orders of magnitude. As a result, tellurium lies far below cadmium on the vertical axis. Deploying 25 TWp of CdTe PV would require the equivalent of 34 years of global cadmium production and 1500 years of global tellurium production at current rate;...... [while] colloidal quantum dot PV: deploying 25TW of PbS QDPV would require the equivalent of only 22 days of global lead production and 6 hours of global sulfur production.This disparity can be attributed to the use of abundant, high-production-volume primary metals and ultra-thin absorber layer.
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[27] Best Research-Cell Efficiencies (rev. 12-18-2014), National Renewable Energy Laboratory, 2014.

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