Perhaps I'll have to try a blackberry emulsion, just to prove a point :-)

The purpose of a photographic dye is to capture light and then to pass the captured energy on to the halide crystal so that it can create a development center. The solar cell dyes I mentioned do exactly the same thing, but with electrode materials like titanium dioxide or indium tin oxide. The principle is the same though, and I would expect them to work to some degree with silver halides.

But not all dyes will do this. Some hang on to the energy. Some no longer absorb effectively when attached to the receiver crystal. Some are incompatible with gelatin. Some mess up the action of developers. Some are highly poisonous. Dyes for colour negative or conventional transparency film are more specialised still, as the bit of dye left behind after it has given up its energy has to play a part in forming the colour in the processed film.

So, the Dyes which allow you to make a medium-to-fast film with a high degree of consistency, a long shelf life and suitable fir a wide range of taking conditions are indeed very specialised chemicals, and expensive to synthesise.

But, dyes which work well enough for a dedicated amateur who otherwise has only expensive or nonexistant options, might be cheaper, more readily available, or even growing on a bush near you.