Glass Transparent conductive oxide CdS CdTe
ENERGY: Magnesium salt may reduce
hazards, costs of producing devices
S
UBSTITUTING MAGNESIUM chloride for toxic
cadmium chloride could free cadmium-telluride solar-cell manufacturers from a costly and hazardous process without sacrificing efficiency, according to a new study. At the heart of a standard CdTe solar cell is a photovoltaic junction formed by the interface between neighboring thin layers of CdS and CdTe. Without processing the layers after deposition, a cell converts incident solar power into electric power with less than 5% efficiency. Manufacturers bump this up to between 10 and 20% using a junction activation step. For more than two decades, activation has relied on CdCl2, usually deposited as a thin coating on the cell’s CdTe layer. When the cell is heated, chloride diffuses through its stacked structure and reforms the physical and electronic characteristics of the cadmium-containing layers, leaving a more efficient photovoltaic junction.
SAFETY BOARD CHIEF IN THE CROSSHAIRS OVERSIGHT: Congress criticizes
CSB chairman, who then announces managerial changes
A
FTER CONGRESSIONAL Republicans called
for his resignation, the head of the Chemical Safety & Hazard Investigation Board (CSB) has begun implementing recommendations for improving how the board operates. CSB Chairman Rafael Moure-Eraso said last week he would quickly adopt managerial modifications to improve the interactions among board members and strengthen their relationships with CSB staff. Rep. Henry A. Waxman (D-Calif.) had proposed those changes a month ago. CSB has already taken steps to implement them, Moure-Eraso told C&EN. His announcement came a week after Republicans in the House of Representatives said Moure-Eraso should quit. “I really believe it is time for you to go,” said Rep. Darrell Issa (R-Calif.), chairman of the House Over-
Photovoltaic junction
Jon D. Major and his colleagues at the University of Liverpool, in England, have now succeeded in activating cells using MgCl2 instead of CdCl2 without any loss of effiCl ciency (Nature 2014, DOI: 10.1038/ nature13435). The replacement salt is “com400 °C pletely benign and much lower cost” than CdCl2, Major said at a press conference. On an industrial scale, MgCl2 is available for less than 1% of the price of CdCl2 and requires no specialized waste disposal. “Why it hasn’t been used before, we genuinely don’t know,” he said. Some aren’t convinced a replacement salt will result in much savings. For example, in a statement released by First Solar, the company that holds the record for CdTe solar-cell efficiency, Chief Technology Officer Raffi Garabedian said that CdCl2 activation “is not a major cost driver in our manufacturing process.” But smaller start-ups could reap benefits from the research, says Alvin Compaan, professor emeritus of physics at the University of Toledo and cofounder of the thin-film photovoltaic developer Lucintech. Major and coworkers “got some impressive results,” Compaan says. “I think it’s a very important advance.”—
CdS Photovoltaic junction Cl
CdTe MgCl2
Schematic of a CdTe solar cell. Inset shows activation with MgCl2.
MATT DAVENPORT
sight & Government Reform Committee, at a turbulent, two-hour committee hearing on June 19. MoureEraso, who has served on CSB for four years, found little congressional support at the hearing. An 84-page report by Issa’s committee staff, which was released at the hearing, describes “serious management deficiencies” at CSB and concludes that a leadership change is “imperative.” Most of its criticism pertains to delayed reports on industrial accidents and disputes among board members and CSB staff, which the report blames on Moure-Eraso and top managers. The report characterizes CSB as inefficient and badly managed with a “toxic” work environment. It includes allegations by unnamed staff members that Moure-Eraso’s leadership is “bullying” and “abusive.” Moure-Eraso is adamant that he will not resign and said he is disappointed in the hearing’s focus. “It did not examine what we are about, the quality of our reports, or whether we have been an agent of change in the chemical industry,” he told C&EN. “That surprised me.” The board has traveled a difficult path since it was created in 1990. Unfunded for nearly a decade, CSB has rarely had a full complement of five board members. Its small budget has been flat, yet its 40 staff members are tasked with finding the root cause of potentially hundreds of chemical-related accidents each year.—JEFF JOHNSON
CEN.ACS.ORG
5
JUNE 30, 2014
CSB
SAFER SALT FOR SOLAR CELLS
Moure-Eraso says he won’t resign.
