Improved Photovoltaic Performance of Cu2znsn(S,Se)4 Solar Cells with Cation Substitution

One of the most important applications of quaternary chalcogenides is their utility as light absorbing materials in the harvesting of solar energy, which is possible because of their high absorption coefficients, suitable optical band gap, low-cost production, and low toxicity. A well-known quaternary chalcogenide that is used in commercial thin film solar cells is CIGS (CuInGa(S,Se)2). However, limited availability of In and Ga seriously limits their application in the mass production of solar cells. On the other hand, inexpensive, non-toxic and earth-abundant photovoltaic materials are of significant interest. In recent times, Cu2ZnSn(S,Se)4 (CZTS) has emerged as an excellent prospect for photovoltaic devices due to its good absorption coefficient, earth abundance, and a suitable band gap. However, precise control of the S/Se ratio is very difficult during the process. Moreover, achieving an appropriate crystal phase and controlled stoichiometry during synthesis is still a big challenge. Furthermore, the formation of non-stoichiometric compositions (secondary phases) are often observed along with the CZTS phase. Thus far, it has been understood that these secondary phases suppress the performance of the device by acting as recombination centers. The aim of this project is to modify the formation energy/density of these defects and/or their location in the energy gap of the CZTS absorber by cation substitution. Incorporation of anions in the structure of CZTS may offer better flexibility and control over the stoichiometry and the crystal phase. The achievements can make substantial progress in developing sustainable kesterite-based solar cells providing environmental and manufacturing benefits.

Project ID:PB10811-0260
External Project ID:MOST108-2622-E182-003-CC3