  The recently demonstrated electroluminescence of color centers in diamond
makes them one of the best candidates for room temperature single-photon
sources. However, the reported emission rates are far off what can be achieved
by state-of-the-art electrically driven epitaxial quantum dots. Since the
electroluminescence mechanism has not yet been elucidated, it is not clear to
what extent the emission rate can be increased. Here we develop a theoretical
framework to study single-photon emission from color centers in diamond under
electrical pumping. The proposed model comprises electron and hole trapping and
releasing, transitions between the ground and excited states of the color
center as well as structural transformations of the center due to carrier
trapping. It provides the possibility to predict both the photon emission rate
and the wavelength of emitted photons. Self-consistent numerical simulations of
the single-photon emitting diode based on the proposed model show that the
photon emission rate can be as high as 100 kcounts s$^{-1}$ at standard
conditions. In contrast to most optoelectronic devices, the emission rate
steadily increases with the device temperature achieving of more than 100
Mcount s$^{-1}$ at 500 K, which is highly advantageous for practical
applications. These results demonstrate the potential of color centers in
diamond as electrically driven non-classical light emitters and provide a
foundation for the design and development of single-photon sources for optical
quantum computation and quantum communication networks operating at room and
higher temperatures.
