news digest ♦ Solar


sulphide and are rigorously optimised to reduce charge- carrier losses from surface defects and to provide the most complete coverage of the solar spectrum.


Nontoxic quantum dots improve solar cells


Solar cells made with low-cost, nontoxic copper-based quantum dots can achieve unprecedented longevity and efficiency


Solar cells made with low-cost, nontoxic copper-based quantum dots can achieve unprecedented longevity and efficiency, according to a study by Los Alamos National Laboratory and Sharp Corporation.


“For the first time, we have certified the performance of a quantum dot sensitised solar cell at greater than 5 percent, which is among the highest reported for any quantum dot solar cell,” says Hunter McDaniel, a Los Alamos postdoctoral researcher and the lead author on a paper appearing inNature Communications.


Schematic of the quantum dot sensitised solar cell (QDSSC) architecture (CISeS QDs are red triangles, the contacts are omitted). This device design avoids QD-to- QD carrier transport completely (limits other QD solar cells), and benefits from more complete light absorption and a modular design


“The new solar cells were certified by the National Renewable Energy Laboratory (NREL) and demonstrated a record power-conversion efficiency for this type of devices,” according to Victor Klimov of Los Alamos, director of the Centre for Advanced Solar Photophysics (CASP), a DOE Energy Frontier Research Centres (EFRC).


Hunter McDaniel, Los Alamos National Laboratory postdoctoral researcher, works in the laboratory developing next-generation quantum dots that could revolutionise photovoltaic technology.


“The robust nature of these devices opens up the possibility for commercialisation of this emerging low- cost and low-toxicity photovoltaic technology,” he notes.


The reported solar cells are based on a new generation of nontoxic quantum dots (not containing either lead or cadmium as do most quantum dots used in solar cells). These dots are based on copper indium selenide


134 www.compoundsemiconductor.net January / February 2014


Current-density versus voltage characteristics of a record QDSSC certified by NREL. Inset: Power conversion efficiency as a function of time since fabrication (showing long term stability) and a transmission electron microscope image of a QD/TiO2 heterojunction.


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