Supporting Information

Transcription

1 Supporting Information Mutual Photoluminescence Quenching and Photovoltaic Effect in Large-Area Single-Layer MoS2-Polymer Heterojunctions Authors: Tejas A. Shastry, 1,3,+ Itamar Balla, 1,+ Hadallia Bergeron, 1 Samuel H. Amsterdam, 2,3 Tobin J. Marks, 1,2,3 and Mark C. Hersam 1,2,3, * 1 Department of Materials Science and Engineering, Northwestern University, Evanston, IL 60208, United States. 2 Department of Chemistry, Northwestern University, Evanston, IL 60208, United States. 3 Argonne-Northwestern Solar Energy Research Center, Northwestern University, Evanston, IL 60208, United States. + These authors contributed equally. *Correspondence to: m-hersam@northwestern.edu S1

2 Figure S1. Determination of percentage of monolayer MoS2. (a) Representative optical micrograph of CVD-grown MoS2 with red, blue, and green circles denoting regions of bilayer/multilayer growth, monolayer growth, and pinholes, respectively. (b) RGB channels for the identified regions were used to determine the pixel counts and monolayer percentage shown in Table S1. In both images, the black scale bar is 20 micrometers. A collection of similar images was used to determine the overall percentage of monolayer MoS2. Table S1. Summary of pixel counts for RGB channels shown in Figure S1. The percentage of total MoS2 area excludes pinholes. Pixel count Percentage of total MoS2 area Percentage of total area Monolayer growth (blue) % 77% Multilayer growth (red) % 22% Pinholes (green) % S2

3 Figure S2. Contact atomic force microscopy of the MoS2 monolayer shows low roughness in the height (left) and micron-sized intersecting grains in the lateral force microscopy retrace (right). Figure S3. Photoluminescence of MoS2 for various thicknesses of PTB7. S3

4 Figure S4. Measured and constructed external quantum efficiency for MoS2-PTB7 heterojunction solar cells. The constructed EQE was modeled using the absorbances of the individual layers from Figure 4d, resulting in a contribution to the total current density of 97% and 3% for MoS2 and PTB7, respectively. S4

5 Figure S5. Optical constants (n and k) for the materials in MoS2/PTB7 solar cells. The constants were obtained from published literature values and the database provided by the authors of the cited IQE calculation method. 1-4 S5

6 Figure S6. Device layer structure and transfer matrix modeling of the MoS2/PTB7 solar cell. ITO thickness was determined by the manufacturer (Thin Film Devices). MoS2 thickness was determined by AFM as described in the main text. The thickness of PTB7 was determined by spin coating various layers and using the published absorption coefficient. Thicknesses for MoOx and silver were determined by the evaporation controller during device fabrication and calibrated with ellipsometry. Transfer matrix modeling was conducted following a previously published method. 1 The active layer absorption in Figure 4 of the main text was calculated by subtracting the parasitic absorbance from the measured active layer absorbance. Parasitic absorbance was determined by subtracting the calculated reflectance and calculated active layer absorption from unity. References 1. Burkhard, G. F.; Hoke, E. T.; McGehee, M. D. Accounting for Interference, Scattering, and Electrode Absorption to Make Accurate Internal Quantum Efficiency Measurements in Organic and Other Thin Solar Cells. Adv. Mater. 2010, 22, Stolterfoht, M.; Philippa, B.; Armin, A.; Pandey, A. K.; White, R. D.; Burn, P. L.; Meredith, P.; Pivrikas, A. Advantage of Suppressed Non-Langevin Recombination in Low Mobility Organic Solar Cells. Appl. Phys. Lett. 2014, 105, Lajaunie, L.; Boucher, F.; Dessapt, R.; Moreau, P. Strong Anisotropic Influence of Local-Field Effects on the Dielectric Response of α-moo3. Phys. Rev. B 2013, 88, Yim, C.; O'Brien, M.; McEvoy, N.; Winters, S.; Mirza, I.; Lunney, J. G.; Duesberg, G. S. Investigation of the Optical Properties of MoS2 Thin Films Using Spectroscopic Ellipsometry. Appl. Phys. Lett. 2014, 104, S6