| AVS 57th International Symposium & Exhibition | |
| Energy Frontiers Topical Conference | Wednesday Sessions |
| Session EN+TF-WeM |
| Session: | CIGS, CZTS and Chalcopyrite Films & Solar Cells |
| Presenter: | S.F. Bent, Stanford University |
| Authors: | A. Wangperawong, Stanford University J.S. King, Stanford University S.M. Herron, Stanford University B.P. Tran, Stanford University K. Pangan-Okimoto, Stanford University S.F. Bent, Stanford University |
| Correspondent: | Click to Email |
Inorganic thin film photovoltaics are an attractive technology for achieving large-scale deployment of inexpensive, stable, and efficient solar cells. However, current leading thin-film materials, such as CdTe and CIGS, face production limitations at a global scale as they contain both non-abundant and toxic elements. A material that has gained significant attention is Cu2ZnSnS4 (CZTS), which is not constrained by the drawbacks of CdTe and CIGS and has an ideal bandgap for a single junction photovoltaic device of 1.4-1.5 eV. Several groups have studied the fabrication of CZTS solar cells using a variety of methods ranging from sol-gel processing to sputter deposition, with a record efficiency of 9.6% recently reported. In the present work, we report an alternative water-based method for large area deposition of CZTS thin films that does not require expensive or complex equipment. Specifically, thin films of CZTS were fabricated on silicon, glass and molybdenum-coated substrates through a combination of chemical bath deposition, ion exchange and sulfurization heat treatment. The film composition could be controlled through a combination of number and length of chemical bath steps and ion exchange time. The resulting samples were analyzed by scanning electron microscopy (SEM), Auger electron spectroscopy (AES), X-ray diffraction (XRD), Raman spectroscopy, inductively-coupled plasma optical emission spectroscopy (ICP-OES), and diffuse reflectance absorption spectroscopy. XRD, Raman, and UV-Vis optical spectra are consistent with the formation of CZTS. The results show that the process produces thin films of CZTS exhibiting uniform composition, well-defined crystal structure, and good optical properties with a bandgap of 1.45 eV. Complete solar cell devices made with chemical bath-deposited CZTS were fabricated. Measurements on these devices exhibit photovoltaic and rectifying behavior, and the results will be discussed.