Solution-based electrical doping of semiconducting polymer films over a limited depth

Abstract

Solution-based electrical doping protocols may allow more versatility in the design of organic electronic devices; yet, controlling the diffusion of dopants in organic semiconductors and their stability has proven challenging. Here we present a solution-based approach for electrical p-doping of films of donor conjugated organic semiconductors and their blends with acceptors over a limited depth with a decay constant of 10-20 nm by post-process immersion into a polyoxometalate solution (phosphomolybdic acid, PMA) in nitromethane. PMA-doped films show increased electrical conductivity and work function, reduced solubility in the processing solvent, and improved photo-oxidative stability in air. This approach is applicable to a variety of organic semiconductors used in photovoltaics and field-effect transistors. PMA doping over a limited depth of bulk heterojunction polymeric films, in which amine-containing polymers were mixed in the solution used for film formation, enables single-layer organic photovoltaic devices, processed at room temperature, with power conversion efficiencies up to 5.9 ± 0.2% and stable performance on shelf-lifetime studies at 60 °C for at least 280 h.

Controlling Molecular Doping in Organic Semiconductors

“…Sequential deposition of the OSC and dopants has several processing advantages. For sequential doping, the dopant molecules could be either evaporated onto a polymer film or deposited from an orthogonal solvent that does not dissolve the polymer film . Small nonpolar dopants such as F4TCNQ evaporated onto P3HT rapidly penetrate the film and diffuse through the entire film thickness because the polymer has significant amorphous domains …”

“…In the listed studies, the authors have generally assumed that these sequential methods produce an essentially homogeneous doping profile through the entire film depth. Diffusion measurements, which will be discussed in Section , suggest that this is a reasonable assumption for small dopants such as F4TCNQ, but not for larger molecules . Therefore, some degree of caution should be used when applying sequential doping techniques for new OSC:dopant systems, particularly with bulky 3D dopants.…”

“…Together, these studies serve to highlight both the complexity and importance of doped film morphology on charge transport, and demonstrate the power of sequential doping methods to minimize morphological disruption. Although sequential doping has been successfully applied to several polymer:dopant systems, further work is needed to verify if this technique can be used to control the dopant anion location within the OSC matrix. In the near future, we expect to see more studies evaluate the use of sequential doping to control structure and morphology in OSC films.…”

Interface Exciplex Anchoring the Color Stability of Solution‐Processed Thermally Activated Delayed Fluorescent White Organic Light‐Emitting Diodes

“…In order to fabricate highly efficient solution‐processed OLEDs, the charge carrier transport interlayer is the key to decreasing the driving voltage and then boost the device performance . We have developed the mixed hole transport interlayer based on PVK and TFB and successfully improved the performance of solution‐processed panchromatic OLEDs in previous work .…”

An Amidine‐Type n‐Dopant for Solution‐Processed Field‐Effect Transistors and Perovskite Solar Cells

“…[1][2][3] The strategy has been employed to demonstrate efficient optoelectronic devices, such as organic light-emitting diodes, [4] organic thin-film transistors (OTFTs), [5] organic solar cells, [6,7] and perovskite solar cells. [1][2][3] The strategy has been employed to demonstrate efficient optoelectronic devices, such as organic light-emitting diodes, [4] organic thin-film transistors (OTFTs), [5] organic solar cells, [6,7] and perovskite solar cells.…”