Fig. 3: Mechanistic study of n-doping between various ETLs and active layers containing nonfullerene acceptors.
Deconvolution of the N1s peak in XPS spectra of different ETLs coated on ITO substrates: (a) PEIE processed using different conditions: 1.0 vol% CH3COOH and 1.0 vol% NaOH solution (40 mg/mL in H2O) were added in a 6 mg/mL PEIE (H2O) solution to tune the pH value to be around 4 and 12, respectively. Note that all the PEIE samples were thermally annealed at 80 °C in a glovebox for 10 min before performing XPS measurements. b PFN-Br and PFN. c PDIN and PDINO. The experimental N1s curves (bold gray lines) are as-recorded data after Shirley background subtraction, and the dash lines present their best fits by performing multi-peak fittings. d–f Measured EQE spectra of an inverted 500 nm thick PCE10:COTIC-4F device using different ETLs as interlayers (as indicated in the figure legend) or directly blended within the active layer. N2200 and PFN are blended directly into the active layer blend with a weight ratio of ~1:50 (wt/wt). g Summary of n-doping mechanism of NFA containing blends with the ETLs studied in this work, indicating the possible electron-transfer pathways.
