title: Making Record-efficiency SnS Solar Cells by Thermal Evaporation and Atomic Layer Deposition.
abstract: Tin sulfide (SnS) is a candidate absorber material for Earth-abundant, non-toxic solar cells. SnS offers easy phase control and rapid growth by congruent thermal evaporation, and it absorbs visible light strongly. However, for a long time the record power conversion efficiency of SnS solar cells remained below 2%. Recently we demonstrated new certified record efficiencies of 4.36% using SnS deposited by atomic layer deposition, and 3.88% using thermal evaporation. Here the fabrication procedure for these record solar cells is described, and the statistical distribution of the fabrication process is reported. The standard deviation of efficiency measured on a single substrate is typically over 0.5%. All steps including substrate selection and cleaning, Mo sputtering for the rear contact (cathode), SnS deposition, annealing, surface passivation, Zn(O,S) buffer layer selection and deposition, transparent conductor (anode) deposition, and metallization are described. On each substrate we fabricate 11 individual devices, each with active area 0.25 cm(2). Further, a system for high throughput measurements of current-voltage curves under simulated solar light, and external quantum efficiency measurement with variable light bias is described. With this system we are able to measure full data sets on all 11 devices in an automated manner and in minimal time. These results illustrate the value of studying large sample sets, rather than focusing narrowly on the highest performing devices. Large data sets help us to distinguish and remedy individual loss mechanisms affecting our devices.
authors.affiliation: Laboratory for Manufacturing and Productivity, Massachusetts Institute of Technology; Department of Materials Science and Engineering, Massachusetts Institute of Technology; rjaramil@mit.edu.
authors.forename: Rafael
authors.initials: R
authors.lastname: Jaramillo
authors.affiliation: Department of Mechanical Engineering, Massachusetts Institute of Technology; Laboratory for Manufacturing and Productivity, Massachusetts Institute of Technology.
authors.forename: Vera
authors.initials: V
authors.lastname: Steinmann
authors.affiliation: School of Engineering and Applied Sciences, Harvard University.
authors.forename: Chuanxi
authors.initials: C
authors.lastname: Yang
authors.affiliation: Laboratory for Manufacturing and Productivity, Massachusetts Institute of Technology; Department of Materials Science and Engineering, Massachusetts Institute of Technology.
authors.forename: Katy
authors.initials: K
authors.lastname: Hartman
authors.affiliation: Department of Mechanical Engineering, Massachusetts Institute of Technology; Laboratory for Manufacturing and Productivity, Massachusetts Institute of Technology.
authors.forename: Rupak
authors.initials: R
authors.lastname: Chakraborty
authors.affiliation: Laboratory for Manufacturing and Productivity, Massachusetts Institute of Technology; Department of Materials Science and Engineering, Massachusetts Institute of Technology.
authors.forename: Jeremy R
authors.initials: JR
authors.lastname: Poindexter
authors.affiliation: Laboratory for Manufacturing and Productivity, Massachusetts Institute of Technology.
authors.forename: Mariela Lizet
authors.initials: ML
authors.lastname: Castillo
authors.affiliation: Department of Chemistry & Chemical Biology, Harvard University.
authors.forename: Roy
authors.initials: R
authors.lastname: Gordon
authors.affiliation: Department of Mechanical Engineering, Massachusetts Institute of Technology; Laboratory for Manufacturing and Productivity, Massachusetts Institute of Technology.
authors.forename: Tonio
authors.initials: T
authors.lastname: Buonassisi
mesh_terms: D012993:Solar Energy; D013440:Sulfides / Q000737:chemistry*; D017971:Tin Compounds / Q000737:chemistry*; D014835:Volatilization
chemical_list: D013440:Sulfides; D017971:Tin Compounds; C078041:tin sulfide