LANL ANNOUNCES NEW WAY TO GROW HIGH-EFFICIENCY SOLAR CELLS

FROM:  LOS ALAMOS NATIONAL LABORATORY 
Los Alamos Develops New Technique for Growing High-Efficiency Perovskite Solar Cells
Researchers’ crystal-production insights resolve manufacturing difficulty

LOS ALAMOS, N.M., January 29, 2015—This week in the journal Science, Los Alamos National Laboratory researchers reveal a new solution-based hot-casting technique that allows growth of highly efficient and reproducible solar cells from large-area perovskite crystals.

“These perovskite crystals offer promising routes for developing low-cost, solar-based, clean global energy solutions for the future,” said Aditya Mohite, the Los Alamos scientist leading the project.

State-of-the-art photovoltaics using high-purity, large-area, wafer-scale single-crystalline semiconductors grown by sophisticated, high temperature crystal-growth processes are seen as the future of efficient solar technology. Solar cells composed of organic-inorganic perovskites offer efficiencies approaching that of silicon, but they have been plagued with some important deficiencies limiting their commercial viability. It is this failure that the Los Alamos technique successfully corrects.

The researchers fabricated planar solar cells from pervoskite materials with large crystalline grains that had efficiencies approaching 18%, among the highest reported in the field of perovskite-based light-to-energy conversion devices. The cells demonstrate little cell-to-cell variability, resulting in devices showing hysteresis-free photovoltaic response, which had been a fundamental bottleneck for stable operation of perovskite devices.

“Characterization and modeling attribute the improved performance to reduced bulk defects and improved charge-carrier mobility in large-grain pervoskite materials,” said Mohite, “and we’ve demonstrated that the crystalline quality is on par with that observed for high-quality semiconductors like silicon and gallium arsenides.”

The researchers anticipate that their crystal growth technique will lead the field towards synthesis of wafer-scale crystalline perovskites necessary for the fabrication of high-efficiency solar-cells and be applicable to several other material systems plagued by polydispersity, defects and grain boundary recombination in solution-processed thin-films.

The work at Los Alamos National Laboratory was supported by a DOE Office of Basic Energy Sciences proposal and by the Los Alamos National Laboratory Directed Research and Development (LDRD) program. This work was done in part at the Center for Integrated Nanotechnologies, a DOE Office of Science User Facility.

Researchers include Wanyi Nie, Hsinhan Tsai, Jean-Christophe Blancon, Amanda J. Neukirch, Gautam Gupta, Jared J. Crochet, Sergei Tretiak, Hsing-Lin Wang and Aditya D. Mohite of Los Alamos, in addition to Reza Asadpour (Purdue University), Manish Chhowalla (Rutgers Univesity) and Muhammad A. Alam (Purdue University).

LANL ON USE OF QUANTUM DOTS TO IMPROVE SOLAR CELLS

FROM:  LOS ALAMOS NATIONAL LABORATORY
Nontoxic Quantum Dot Research Improves Solar Cells

Record power-conversion efficiency at Los Alamos from quantum-dot sensitized photovoltaics

LOS ALAMOS, N.M., Dec. 10, 2013—Solar cells made with low-cost, non-toxic 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 sensitized solar cell at greater than 5 percent, which is among the highest reported for any quantum dot solar cell,” said Hunter McDaniel, a Los Alamos postdoctoral researcher and the lead author on a paper appearing in Nature Communications this week. “The robust nature of these devices opens up the possibility for commercialization of this emerging low-cost and low-toxicity photovoltaic technology,” he noted.

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

“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 Center for Advanced Solar Photophysics a DOE Energy Frontier Research Centers (EFRC). In addition to CASP-EFRC, this research has been also supported via a cooperative research agreement with Sharp Corporation.

The paper, “An integrated approach to realizing high-performance liquid-junction quantum dot sensitized solar cells” is scheduled for online publication in Nature Communications on Dec. 10, 2013.

The paper's authors are Hunter McDaniel, Nikolay S. Makarov, Jeffrey M. Pietryga, and Victor I. Klimov of the Center for Advanced Solar Photophysics, Los Alamos National Laboratory, in partnership with Nobuhiro Fuke of the Materials & Energy Technology Laboratory, Sharp Corporation, Japan.