Figure 4
Cross-sectional transmission electron microscope (TEM) images of hybrid organic tandem solar cells. Cross-sectional TEM image of (a) spin-coated and (b–d) transfer-fabricated tandem solar cells. (c) and (d) are the images of the regions enclosed by black and red squares in (b), respectively. For the transfer-fabricated device, thicknesses of the transferred PCPDTBT:PC70BM layer (i) and the thermally evaporated small-molecule layers (ii) were unchanged from the designed values. The features (iii) and (iv) in (d) were generated during focused-ion beam milling used in sample preparation.
