Fig. 3
Morphology of the mixed-quantum-dot structure for balanced carrier extraction. a Cross-section of a mixed film with different QD donor/acceptor ratios. Blue and red spheres represent acceptor and donor QDs, respectively. b Distribution of path lengths for a 1:1 A- to D-type QD ratio. For this configuration, the shortest path (normalized to thickness) is 1.1, and the median length of 1.14. c Slices of mixed CQD solids with different D/A ratios representing the dominant presence of each type of QD. d Normalized path length as a function of A- to D-type QD ratio within a mixed QD film. Error bars represent the standard deviation of the 10 shortest different path lengths for each A/D configuration. e Balanced extraction (β = 1) requires a compromise between electron and hole mobilities and their respective path-lengths. A maximum power conversion efficiency is expected when the carrier extraction is balanced (Supplementary Fig. 14)
