Figure 5: Measuring the LD of CuPc.
(a) Architecture for the planar heterojunction OPV based on the donor-acceptor pairing of CuPc-C60. (b) Comparison of the extinction coefficients for CuPc and C60 as well as the spectrum of the LED pulse (λpeak=735 nm) used to pump CuPc. (c) Photovoltage rises recorded when pumping CuPc with the λ=735 nm LED at intensities of 62.7 mW cm−2 (black), 100.4 mW cm−2 (red) and 142.8 mW cm−2 (blue). (d) Relationship between charge carriers and voltage in the CuPc-C60 device obtained using the charge extraction method and an exponential fit to the data. The error bars represent the standard deviation across eight devices. (e) Simulated ηAηD curves for three CuPc LD values with a constant C60 LD of 12.1 nm compared with the time integrated LED pump spectrum. (f) Comparison of the predicted number of charge carriers generated (for multiple values of the CuPc LD) to the photovoltage-based measurement (horizontal line). The VOC (in millivolts) that would be measured for the corresponding number of charge carriers is labelled for each bar.
