Well, I'm not sure if I completely understand your question. Do you mean in relation to solar energy conversion, or Tesla's works?
If the former, the use of exotic Group II-VI elemental alloys are falling by the wayside (e.g. CdTe), and the focus is going in the direction of finding better geometries in creating semiconductor layers with Silicon, since the cost of it has dropped immensely and there are great advances in growing crystals and molecular deposition methods. But even then, it is a struggle to get efficiencies beyond 45%. That's because of heat. I'm actually in the middle of studying the physics of semiconductors now, so in a few months, I might be able to go more into depth on the subject. I believe there was a thread somewhere on here where we discussed the latest progress in that field more.
If the latter, the only people who are taking Tesla's electricity ideas seriously, AFAIK, are those on YouTube who are trying to capture the "free energy" using various coil configurations. Sadly, they are not going to get far in creating anything that achieves what are known as "over unity" devices. It is a violation of laws of physics (such as conservation of energy). Science still has a poor understanding of electricity and fields in general, as well. However, as I suggested, Tesla's mechanical ideas are being explored with interest like his valve and turbine, which both work on similar principles of using turbulence as the driving mechanism. Those ideas could be used to increase efficiencies of hydroelectric generators, for example. That's because the only "free" energy we have at our disposal are what are known as scalar potentials, like gravity.
I can't say I am that familiar with the grand body of works Tesla achieved, though, so I'm still as much in the dark as most. I'm actually pursuing ideas that incorporate the natural dipole created by water molecules falling through coils to create electricity. This effect is best demonstrated with Kelvin's Water Drop apparatus. Taking that idea and working on improving efficiencies could make something as simple as rain into a source of viable power without need for dams and bulky mechanical generators. However, my exploration in that is still in its infancy. I have much to learn still and I may be chasing a wild-goose. 
Doer was right. The EM interference would make wireless communication damn near impossible, if you're talking about that crazy tower he was building for JP Morgan.
Or are you referring to something more subtle?
just to show you I was justified in my response to doer,
paper written by Theodor C. Loder, III, Professor Emeritus at the Institute for the Study of Earth, Oceans and Space at the University of New Hampshire. He outlined the importance of these concepts in his paper titled
Space and Terrestrial Transportation and Energy Technologies For The 21st Century (2).
There is significant evidence that scientists since Tesla have known about this energy, but that its existence and potential use has been discouraged and indeed suppressed over the past half century or more (2) – Dr. Theodor C. Loder III
Harold E. Puthoff, an American Physicist and Ph.D. from Stanford University, as a researcher at the institute for Advanced Studies at Austin, Texas published a paper in the journal
Physical Review A, atomic, molecular and optical physics titled “Gravity as a zero-point-fluctuation force
(3)” . His paper proposed a suggestive model in which gravity is not a separately existing fundamental force, but is rather an induced effect associated with zero-point fluctuations of the vacuum, as illustrated by the Casimir force. This is the same professor that had close connections with Department of Defense initiated research in regards to remote viewing. The findings of this research are highly classified, and the program was instantly shut down not longer after its initiation
(4).
Another astonishing paper titled “Extracting energy and heat from the vacuum,” by the same researchers, this time in conjunction with
Daniel C. Cole, Ph.D. and Associate Professor at Boston University in the Department of Mechanical Engineering was published in the same journal
(5).
Relatively recent proposals have been made in the literature for extracting energy and heat from electromagnetic zero-point radiation via the use of the Casimir force. The basic thermodynamics involved in these proposals is analyzed and clarified here,
with the conclusion that yes, in principle, these proposals are correct (5).
Furthermore, a paper in the journal
Physical Review A, Puthoff titled “Source of vacuum electromagnetic zero-point energy
(6),” Puthoff describes how nature provides us with two alternatives for the origin of electromagnetic zero-point energy. One of them is generation by the quantum fluctuation motion of charged particles that constitute matter. His research shows that particle motion generates the zero-point energy spectrum, in the form of a self-regenerating cosmological feedback cycle.
