Zero-Reabsorption Doped-Nanocrystal Luminescent Solar Concentrators

Abstract

Optical concentration can lower the cost of solar energy conversion by reducing photovoltaic cell area and increasing photovoltaic efficiency. Luminescent solar concentrators offer an attractive approach to combined spectral and spatial concentration of both specular and diffuse light without tracking, but they have been plagued by luminophore self-absorption losses when employed on practical size scales. Here, we introduce doped semiconductor nanocrystals as a new class of phosphors for use in luminescent solar concentrators. In proof-of-concept experiments, visibly transparent, ultraviolet-selective luminescent solar concentrators have been prepared using colloidal Mn(2+)-doped ZnSe nanocrystals that show no luminescence reabsorption. Optical quantum efficiencies of 37% are measured, yielding a maximum projected energy concentration of ∼6× and flux gain for a-Si photovoltaics of 15.6 in the large-area limit, for the first time bounded not by luminophore self-absorption but by the transparency of the waveguide itself. Future directions in the use of colloidal doped nanocrystals as robust, processable spectrum-shifting phosphors for luminescent solar concentration on the large scales required for practical application of this technology are discussed.

Limits of Visibly Transparent Luminescent Solar Concentrators

“…For example, in Mn-doped ZnSe/ZnS core/shell NCs, small amount (0.1-1%) of Mn 2+ introduces new localized excited energy states within the bandgap of ZnSe resulting in exhibit enhanced downshifted luminescence. [9] Ternary or quaternary compound semiconductors are also introduced in core/shell QDs, such as CdSe/Cd x Pb 1-x S [73] and CuInSe x Se 2-x /ZnS QDs. [12] Among quantom dot emitters, a new class of emitter materials has been reported recently based on 0D nanoclusters and nanocluster nanocrystals for these applications.…”

“…[3] This work has been subsequently followed by a number of other groups. [8][9][10][11][12] In contrast to transparent photovoltaics, which have also been developed to exploit this untapped area, [13][14][15] this new concentrator approach offers an alternative pathway whereby energy is transported optically, offering a simple route to large-area manufacturing, high defect tolerance, angle independent performance, and low-level energy cost. In this progress report we discuss the theoretical limits of transparent LSCs, idealized configurations, scalability, and properties of enabling materials.…”

Spectral light management for solar energy conversion systems

“…Recently it has been showed that Mn 2+ -doped ZnSe nanocrystals can work as phosphors that show no luminescence reabsorption for use in LSCs [38] (Fig. 5b).…”

Advancing colloidal quantum dot photovoltaic technology

“…Another demonstration used Mn 2+ -doped ZnSe/ZnS core-shell CQD structures in a LSC system [268]. Due to a large difference in the absorptivity between the Mn 2+ ion inclusions and the ZnSe, a Stokes shift of 1 eV was obtained.…”