Establishing Self‐Dopant Design Principles from Structure–Function Relationships in Self‐n‐Doped Perylene Diimide Organic Semiconductors

Abstract

Self‐doping is a particular doping method that has been applied to a wide range of organic semiconductors. However, there is a lack of understanding regarding the relationship between dopant structure and function. A structurally diverse series of self‐n‐doped perylene diimides (PDIs) is investigated to study the impact of steric encumbrance, counterion selection, and dopant/PDI tether distance on functional parameters such as doping, stability, morphology, and charge‐carrier mobility. The studies show that self‐n‐doping is best enabled by the use of sterically encumbered ammoniums with short tethers and Lewis basic counterions. Additionally, water is found to inhibit doping, which concludes that thermal degradation is merely a phenomenological feature of certain dopants, and that residual solvent evaporation is the primary driver of thermally activated doping. In situ grazing‐incidence wide‐angle X‐ray scattering studies show that sample annealing increases the π–π stacking distance and shrinks grain boundaries for improved long‐range ordering. These features are then correlated to contactless carrier‐mobility measurements with time‐resolved microwave conductivity before and after thermal annealing. The collective relationships between structural features and functionality are finally used to establish explicit self‐n‐dopant design principles for the future design of materials with improved functionality.

Probing Excited State Delocalization and Charge Separation in Hierarchical Perylene Diimide Materials with Time-Resolved Broadband Microscopy

“…Also present in the KT-PDI spectrum are two peaks at 735 and 820 nm, which are also observed in solution-phase measurements (Figure S2) of the aggregate upon electrochemical reduction. These two peaks are assigned to vibronic transitions of the electron polaron and indicate the presence of persistent reduced species from the redox-assisted self-assembly or alternatively self-n-doping behavior that has been previously shown in solid-state PDI with similar imide functionalizations. , …”

“…These two peaks are assigned to vibronic transitions of the electron polaron 42 and indicate the presence of persistent reduced species from the redox-assisted self-assembly or alternatively self-n-doping behavior that has been previously shown in solid-state PDI with similar imide functionalizations. 43,44 Polarization Dichroism. To provide insight into the microscale order of the two samples, we next turned to polarization-resolved brightfield microscopy.…”

The Quest for Air Stability in Organic Semiconductors

“…For p-doped OSCs, these ionizable functional groups are typically sulfonic acids that provide protons for oxidation while the sulfonate stabilizes the hole polaron on the polymer backbone . Self-n-doped materials with tethered ammonium groups and Lewis basic counterions were also widely reported. , …”

“…63 Self-n-doped materials with tethered ammonium groups and Lewis basic counterions were also widely reported. 64,65 2.2. Electrochemical Doping.…”

Self‐Doping of the Transport Layers Decreases the Bimolecular Recombination by Reducing Static Disorder

“…[9] Self-doping enhances the electronic conductivity [10,11] without the drawbacks of the extrinsic doping such as demixing, poor diffusivity, and aggregation of the dopants. [12] As an example, N-oxide bearing 2,9-bis [3-(dimethyloxidoamino)propyl]anthra[2,1,9-def:6,5,10d 0 e 0 f 0 ]diisoquinoline-1,3,8,10(2H,9H)-tetrone (PDINO) is a selfdoped ETL. It has been demonstrated to have Ohmic contact when used with poly[ [4,8- Electron-transport layers (ETLs) have a crucial role in the solar cells' performance.…”