The exited electron is an electron moving through the conducting band, a superposition of excited states of single atoms. So there is a negative charge "moving" in the solid.

Because overall, the solid is neutral, the rest of the solid has one electron less than is necessary to cancel the positive charge of the nuclei. So somewhere is an "empty" state that can "move" through the solid as well.

Personally, I have less problems imagining two physical charges than I have imagining the "particle" character of both because both are highly delocalized.

Well if you think about it, most phenomena is actually based upon movement of something that was there before and now isn't. As Erik said, an empty state is moving through a solid.

Because electrons are real, and an electron is a part of an exciton.

Elaborating more on your question:

a Hole is a particle which does n't have mass but does have electric charge. Is a charged quasiparticle with a charge value of +1.602 x10^-19 C .

Quasiparticles may (or may not) have individual electric charge, regardless whether the particle has zero or non-zero mass.

Holes have zero inertial and rest mass, although an effective mass can be assigned to them.

It is true that holes are more of a mathematical-physical trick than a real particle.

Regards !

There are two types of excitons - Vanier- Mott excitons and Frenkel excitons. For simplicity, let's consider free Vanier-Mott excitons. At a certain crystal temperature, (or due to a bombardment with a photon flow) you may have free electrons and holes within c and v energy bands.

A hole is not a 'void' or an 'abstraction'. As you know, there are internal and external energy shells or electron orbits (like s electrons, p electrons, etc. ) for every atom in a crystal (including impurity atoms) electrons on the outermost shells of neighboring atoms space overlap with each other creating hybridized shells between closest atom neighbors being in the essence responsible for the physical / chemical integrity of the crystal.

Those outer shells could be either a co-valent type, or an ion type. For instance, Si, Ge, diamonds have strong co-valent bonds. If an electron for any reason removed away from such a shell, the charge balance (or electroneutrality of the neighboring nucleus and all their shells gets broken and the outermost shell gets unstable. To return stability, it tries to capture an electron from another closest pair of neighbors' outermost shell, because their wave functions are partially overlapped. That is, a non- saturated bond became saturated back but it looks like the non-saturated bond made a leap from one pair of neighbors to another one.

Needless to say that this process can spread far from the place it was originated in the crystal. Once this 'hole' (which is in the essence a non-saturated outer shell between arbitrary neighboring atoms) turned out to be in a certain proximity of a free electron, they feel Coulomb attraction and create a mutual bound (a dipole, or a hydrogen-like atom) being a free quasiparticle called an exciton.

Thanks to all of you for pouring in valuable thoughts on this. I think I'm getting a better sense to this concept. However, there is still a stumbling block (perhaps) in the way I'm visualizing it.

Consider this - When a charge '-q' moves in space from one point in space to the other, what does it leave back at its original point, zero charge or +q charge?

Moreover, considering an atom as the system (electrically neutral) within which, say, an electron makes transition from one state to the other, doesn't creation of hole with the positive charge disturb the net charge neutrality of the system?

Still trying my best to make peace with the thought.

Considering the second part of the above question, this is basically the whole point of excitation and energy flow between a so-called positively and negatively charged particles.

The first part is a bit tricky. I would say that a leaving of a -ve charges will make the vicinity of that area more positively charged than before.

Well, this is really a nice topic, because it touches some fundamental aspects of natural sciences, namely the questions "What is reality?" and "What is truth?" -- which means that this discussion is permitted to become a bit philosophical.

So, where to start from? What do we know for sure? For example, we know that materials vary in their electric conductivity. And we know that current flow gets influenced when traversing a perpendicular magnetic field. This is employed in Hall measurements. Surprisingly, there are some materials that behave completely different from all others in that for them, the sign of the Hall voltage is reversed.

As another example, we know the (low-temperature) luminescence spectra of some materials, especially semiconductors, showing additional features below the band-gap energy. And we see that these spectra occur somewhat shifted to lower energy if additional defects in such materials are present.

However, I deliberately stop here, because all further steps involve interpretations already. Of course there is a standard interpretation for such observations, but since the basic ingredients of these interpretation, namely holes and excitons, are questioned right from the beginning, I'm trying to do without these.

Now, to continue the discussion, here is my question to you: Is there a part of reality (i.e., of what we know for sure) missing in my consideration so far? What about electrons, for example: How real are they -- in the present context of solid-state physical phenomena?

That escalated quickly @Wagner :)

Concerning reality of a hole, if you consider a positively charged ion as something real, then a hole is a positively charged ion in vicinity of other atoms. What is specific for this ion is that taking electron from neighbouring atom, the ion becomes an atom and the neighbouring atom becomes an ion. Exciton is a hydrogen like system, conditioned by Coulomb interaction between the ion and free electron, where only charges and dielectric constant (for Wannier-Mott exciton) of the material between these charges is important (in first instance). Again, in reality, the ion does not move through the crystal, but that positive charge moves from atom to atom. And this REAL positive charge moving through the crystal is called a hole and, formally, in mathematical description, has no principal difference from a free electron. By the way, the so called free electron itself in crystal is almost as fictional as a hole.

@Saransh Gupta ["Considering an atom as the system (electrically neutral) within which, say, an electron makes transition from one state to the other, doesn't creation of hole with the positive charge disturb the net charge neutrality of the system?"]: Let's have a look at p-type doping: An electron makes a transition from the valence band into an empty acceptor state. Of course, the material as a whole stays electrically neutral; nevertheless, the conductivity obtained effectively comes from positive charges (as can be verified by Hall effect measurements).

So, this is just one example for what is highly relevant in this discussion: "There is no way to describe conductivity in metals and semiconductors with classical physics!" (Prof. H. Föll; cf. https://www.tf.uni-kiel.de/matwis/amat/mw2_ge/kap_2/backbone/r2_1_3.html) And of course this also means that there is no way to understand conductivity in metals and semiconductors just on the basis of classical physics.

When metal is considered consisting of an (almost) homogeneous electron sea with periodic positioning of metallic cores, if the metallic cores are kept aside (as long as electron wave scattering by the cores are not considered) for consideration, equivalent of an electron charge missing from somewhere in this electron sea is exactly equivalent to a positive charge exactly in that location amidst of "homogeneous" electron sea. this is actually hole. For intrinsic semiconductor, one hole must be associated with one "misplaced" electron also, and for extrinsic one, this hole i.e. deficiency of electron (supplied by donor atom) is due to deficiency of one positive charge at core .

(had the donor been of higher atomic number by margin of 1, this foreign atom would have contributed to electron sea the same number of electrons by neighboring matrix atoms)

although as a matter of fact, electron is moving from neutral atom to positively charged atom (or electron unsaturated/deficient bond, as you may prefer to call it), the initial and final states of this transfer is very well-conveniently modelled as movement of a net positive charge amidst of an electron sea dotted with positive ionic cores;and as per the philosophy of mathematical modelling, the hole model is granted.

Metallic room temperature hall effect can be conveniently described without referring to quantum mechanics, up to college level (In Indian Subcontinent college textbooks, at least!), but for holes as charge carriers, a formal discussion based on Brillouin zones and E-K diagram curvature relation with electron effective mass is required, which is obviously beyond realms of classical mechanics, due to extensive use of De-Broglie wave for the beginning.