Nanotechnology Based Thin-film Photovoltaics

Since their development in the 1970s, thin film photovoltaics have been an attractive low material cost technology well suited for producing clean and sustainable energy. Through the SEIGERT program, Purdue University, in collaboration with the University of Texas at El Paso, is engineering thin film photovoltaic devices, with a focus on high efficiency absorbers like cadmium telluride (CdTe) and copper indium gallium sulfoselenide (CIGSSe), as well as earth-abundant copper zinc tin sulfoselenide (CZTSSe). Close space sublimation allows the controlled growth of graded ZnCdTe with mono-crystalline CdTe pillars. These nanostructures act as a buffer to reduce defects between the CdTe absorber and its window layers, improving device performance. Synthesis of nanocrystalline CIGSSe and CZTSSe solar absorbers via highly scalable solution-based processes produces versatile nanoparticle inks that can be uniformly coated on almost any surface—including flexible substrates. These coatings can be applied by many techniques including doctor blading, spray coating, and inkjet printing. By improving the nanocrystalline solution based process, CIGSSe and CZTSSe have reached efficiencies of 14.3% and 9.2% respectively. Interdisciplinary electrical, material, and optical characterization of completed devices have enhanced our physical understanding of these thin film photovoltaic absorbers, allowing for a holistic approach to developing this technology.