Hydrogen Selenide Selenization in CIGS Factories: A Highly Toxic Gas

… more less Hydrogen selenide selenization is a common way to turn metal films into a CIGS absorber. The factory first sputters copper, indium and gallium onto the substrate. Then it heats the stack to roughly 400 to 500 degrees C in a furnace filled with H2Se gas. Selenium from the gas reacts with the metals and forms the CIGS crystal. Hydrogen gas is left over. For a simple copper indium film: Cu + In + 2H2Se -> CuInSe2 + 2H2. H2Se is one of the most toxic gases used in industry. Even tiny amounts in air harm the lungs and eyes, so a leak is a danger to workers and neighbors. Plants control it with sealed gas cabinets, leak sensors that shut valves, and exhaust treatment. The exhaust passes through burners or wet scrubbers that turn H2Se into solid selenium or selenium salts, which are then collected. Some factories avoid the gas by heating the films in plain selenium vapor. That is much less hazardous but harder to control. Sulfur can also replace part of the selenium. After this Concept you can explain why H2Se is used, what makes it dangerous, and how factories contain or replace it.