Figure 5.

a) STEM images (from left: carbon, oxygen, sulfur, and fluorine) for PTB7‐Th:PC₇₁BM BHJ films: (1) as‐prepared, (2) illuminated with simulated solar light (air mass 1.5G, 100 mW cm⁻²) without UCF for 120 min, and (3) illuminated with simulated solar light (air mass 1.5G, 100 mW cm⁻²) with UCF for 120 min. b) Atom compositions (from left: carbon, oxygen, sulfur, and fluorine) obtained by integrating the area (4.3 μm 4.3 μm) of STEM images in panel (a) (note that “1,” “2,” and “3” in the horizontal axis correspond to (1), (2), and (3) in panel (a)).