On the Relationship of the Effective Mobility and Photoconductance Mobility in Organic Solar Cells - Supplementary Information

The efficiency of organic solar cells has increased significantly in the recent years due to the continued improvement in material properties, including the charge carrier mobilities within the bulk heterojunction....


S1.3 Device Characterization
Current-voltage (J-V): J-V measurements of the studied solar cells were performed using a LabVIEWcontrolled Keithley 2400 SourceMeter under the illumination of a white-light LED array.
Impedance: The impedance measurements were performed using a Keysight E5061B Vector Network Analyser in the frequency range from 50 Hz to 10 MHz under the illumination of a white-light LED array. The 85032E Type N kit was used for the instrument calibration, and the presence of the test fixture was compensated for using the "Open," "Short," and "50 Ohm" measurements.
Capacitance-frequency spectra of the studied solar cells were generated from the impedance measurements at various light intensities and applied biases (cf. Fig. S11 -S19). The integration of the 2 capacitance over the voltage range yields the charge carrier density n: where q is the elementary charge, A is the device area, L is the active layer thickness, V sat is the saturated voltage (usually V sat ≤ 0 V), C b is the frequency dependent barrier capacitance obtained via the impedance measurements, C g is the geometric capacitance resulting from the electrodes of the device forming a plate capacitor, and V cor is the voltage corrected for the series resistance R series .
More details related to this technique can be found in Ref. [1]. In this study, nine different organic solar cells were investigated over a wide range of light intensities.
Namely, solar cells based on P3HT:PC 60 BM, PM6:Y11-N4, PM6:Y5, PPDT2FBT:Y6, PM6:Y11, PM6:N4, and PM6:Y6, the latter with varying electron transport layers and thicknesses, were fabricated (cf. Fig. S1).  Figure S1: Experimentally determined values for µ ph (black squares; cf. Eq. 4 in the main manuscript) and µ exp eff (V OC ) (red circles; cf. Eq. 3 in the main manuscript) for various organic solar cells. Calculation of the maximum and minimum mobilities determined via the harmonic and geometric approach (µ har max , µ har min : green dots, cf. Eq. 8 and Eq. 9 in the main manuscript; µ geo max , µ geo min : orange dash-dots, cf. Eq. 11 and Eq. 12 in the main manuscript) and for the relationship µ exp eff = 0.5 · µ ph (gray squares; cf. Eq. 6 in the main manuscript). The horizontal lines show the electron (µ n : blue) and hole (µ p : red) mobilities determined via the SCLC method of single carrier diodes. These mobilities are shown as horizontal lines due to the unknown charge carrier density at which they were measured.