Parts‐per‐Million‐Level Doping Effects in Organic Semiconductor Films and Organic Single Crystals

Abstract

Controlling the pn-type behavior of a semiconductor such as silicon by adding an extremely small quantity of an impurity (doping) is a central part of inorganic semiconductor electronics since the 20th century. Recent progress in the doping of organic semiconductors strongly suggests the advent of a new era of doped organic semiconductors. Here, the principles and effects of doping at the level of parts per million (ppm) in organic semiconductor films and single crystals are described, including descriptions of complete pn-control, doping sensitization, ppm doping using an extremely low-speed deposition technique reaching 10 nm s , and emerging ppm-level doping effects, such as trap filling, majority carriers, homojunction formation, and decreased mobility, as well as ppm-level doping effects in organic single crystals measured by the Hall effect, which shows a doping efficiency of 24%. The Wannier excitonic doping of organic single crystals possessing band conduction and the defect science of organic single crystals related to carrier trapping and scattering are introduced as a new scientific field. The dawn of organic single-crystal electronics is also discussed.

Molecular Semiconductors for Logic Operations: Dead‐End or Bright Future?

“…TIPS‐PEN 4 is representative of high quality crystals with a low g value of 0.3% . The link between mobility values and the defects and disorder within single crystal remains somewhat unexplored, so far . Another characteristic of molecular semiconductors is that they often form polymorphs.…”

“…Obviously a better control of crystal defects is needed because the current quality of organic single crystals used for transport experiments is too low. In undoped single crystals of rubrene 3 , the observed carrier concentration is of ≈10 15 cm −3 , whereas it is only on the amount of ≈10 10 cm −3 for undoped Si . To lower crystal defects, the first step is to start from ultrapure samples obtained by zone refining .…”

“…With such samples in hand, considerable efforts must also be invested in the understanding of crystal growth mechanisms as a function of experimental conditions. To this end, directional crystal growth methods are preferable, e.g., epitaxial growth under ultraslow deposition rate on the order of 10 −9 nm s −1 , crystal growth in a thermal gradient by the Brigdman method or edge casting under slow evaporation conditions . Organic chemists can also contribute by designing and synthesizing novel molecular semiconductors more resilient to defects and disorders at Section .…”

The Impact of Dipolar Layers on the Electronic Properties of Organic/Inorganic Hybrid Interfaces

“…[180,181] An in-depth discussion of doped adsorbate layers, however, goes beyond the scope of the present review and we refer the reader to recent, more specialized papers. [182][183][184][185]…”

Electronic and Crystallographic Examinations of the Homoepitaxially Grown Rubrene Single Crystals

“…This is true not only for conventional inorganic semiconductors; in fact, a monumental work on bromine-doped perylene enkindled the dawn of "organic semiconductor" research [1,2] and led to the discovery of conductive polymers [3], charge transfer complexes [4,5], and molecular superconductors [5][6][7][8]. Although ordinary organic (opto-)electronic devices have been designed using intrinsic organic semiconductors without any intentional doping, on-demand introduction of dopants into molecular semiconductor materials is a long-standing topic in this research field (for review, see e.g., [9][10][11][12][13][14]).…”