Novel Cerium‐Based p‐Dopants with Low Parasitic Absorption for Improved Organic Devices

Abstract High electrical conductivity and improved charge carrier injection enabled by molecular doping are pivotal for high‐performance, energy‐efficient, and stable organic optoelectronic devices. Molecular doping is a key element in device design and manufacturing of active‐matrix organic light‐emitting diode displays, a multi‐billion dollar market. However, it is an inherent feature of state‐of‐the‐art small molecule dopants and their charge‐transfer complexes to strongly absorb in the visible and near‐infrared spectral range. This parasitic effect results in absorption losses, reducing the performance in light‐harvesting and light‐emitting applications. Here, a novel class of vacuum‐processable cerium‐based p‐dopants with excellent processing properties and competitive doping strength even in organic hole transport layers with low‐lying valence levels is presented. A substantial reduction in parasitic absorption for layers doped by the new dopants in the visible and near‐infrared range is found. The reduced polaron absorption of the dopant anions is in excellent agreement with theoretical simulations. By incorporating these dopants into near‐infrared narrowband organic photodetectors, the specific detectivity can be increased by one order of magnitude compared to devices with the established dopant 1,3,4,5,7,8‐hexafluorotetracyanonaphthoquinodimethane (F ₆ ‐TCNNQ). The decreased parasitic absorption yields optical‐microcavity‐enhanced photodetectors with significantly reduced full‐width at half maximum, paving the way toward more efficient and wavelength‐selective infrared detectors.