(a) Active molecules used within this study and their absorption spectra calculated from refractive index values measured by spectroscopic ellipsometry. (b) An energy level diagram for a SubPc/C60 device with an α-NPD exciton dissociation layer inserted between the SubPc and MoO3 layers.
Modeled (a) electric field, (b) exciton generation, and (c) exciton population density profiles within the OPV device used in this study. Boundary conditions (which only affect the exciton population density) at the SubPc/MoO3 or SubPc/α-NPD interface are shown for both perfect exciton reflection (dρ/dx = 0) and 100% exciton quenching or dissociation (ρ = 0).
(a) Device structures for α-NPD/SubPc/C60, SubPc/C60, and α-NPD/SubPc OPV cells. (b) J-V data under 1-sun illumination for α-NPD/SubPc (squares), SubPc/C60 (triangles), and α-NPD/SubPc/C60 (circles) devices. (c) For each device, experimental EQE data (solid lines) are compared to model (dashed lines).
Experimentally determined absorption and emission spectra for SubPc/Spacer/MoO3 stacks deposited on glass. Inset: normalized quantum yield measurements for each stack. Quantum yield was determined using no spacer as well as spacers of BCP and α-NPD.
Experimentally determined (a) J–V, (b) EQE, and (c) IQE data for glass/ITO/MoO3 (5 nm)/α-NPD (x nm)/SubPc (13 nm)/C60 (36 nm)/BCP (10 nm)/Al (100 nm). Three α-NPD thicknesses are shown: 0 nm (triangles), 2 nm (squares), and 5 nm (circles). Modeled EQE and IQE (dotted lines) are shown with three possible boundary conditions at the SubPc/MoO3 or SubPc/α-NPD interface: 100% quenching, exciton reflection (Single HJ), and 100% dissociation (Cascade).
Dependence of (a) J sc, EQE at λ = 585 nm, (b) V oc, FF, and (c) PCE on α-NPD layer thickness for a device comprising glass/ITO/MoO3 (5 nm)/α-NPD (x nm)/SubPc (13 nm)/C60 (36 nm)/BCP (10 nm)/Al (100 nm). Error bars represent standard deviations calculated from a sample size of > 8 devices.
AFM images of (a) ITO/MoO3 (5 nm), (b) ITO/MoO3 (5 nm)/α-NPD (5 nm), (c) ITO/MoO3 (5 nm)/SubPc (13 nm), and (d) ITO/MoO3 (5 nm)/α-NPD (5 nm)/SubPc (13 nm). (e) Grain size and R rms values for each sample and (f) XRD scans of MoO3 (5 nm)/SubPc (13 nm) and MoO3 (5 nm)/α-NPD (5 nm)/SubPc (13 nm), as well as a crystalline control sample of 13 nm SubPc annealed for 15 min at 95 °C.
Literature and fitted values of exciton lifetimes and diffusion lengths for active materials used in this study.
Champion solar cell performance data for the structure: Glass/ITO/MoO3 (5 nm)/α-NPD (x nm)/SubPc (13 nm)/C60 (36 nm)/BCP (10 nm)/Al (100 nm) under simulated 1-sun, AM1.5 G illumination.
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