The market for high concentration photovoltaics (HCPV) remains full of promise, venture funding, and hope. What the CPV market has not shown is revenue. And profit.

We'll get back to that in a moment.

Solar Junction just announced the close of a $19.2 million round D from new investor and strategic partner IQE for scaling up production of high-efficiency multi-junction cells for the CPV market. Existing investors New Enterprise Associates (NEA), Advanced Technology Ventures (ATV), and Draper Fisher Jurvetson (DFJ) also participated in the round. Solar Junction's strategic investor in this round, IQE, has expertise in high-volume epitaxy.

Solar Junction's CEO, Jim Weldon, claims to have "multi-megawatt orders" for the firm's world-record-efficiency III-V multi-junction solar cells based on lattice-matched dilute nitrides. Solar Junction’s world-record cell has an NREL-validated efficiency of 43.5 percent and the company has a roadmap to 50 percent efficiency within the decade.

Efficiency is always important in photovoltaics, but it's probably even more important in CPV. According to Solar Junction, a one percent improvement in efficiency at the cell level can result in a three percent to four percent reduction in the cost of the system -- and further improvements could improve cost in an accelerated, non-linear fashion.

Other developers of CPV chips include established vendors Emcore, Spectrolab, Azure Space  and newcomers like JDSU, Cyrium, Spire, and Semprius. Solar Junction is working with Semprius and has inked an agreement to deliver multi-megawatts of epitaxial wafers. Semprius claims to have set the world-record CPV solar module efficiency using Solar Junction's epi materials.

In the last few months, a number of CPV firms have managed to close investment rounds:

* CPV systems developer GreenVolts won $20 million from ABB in a $30 million round.

,* Semprius closed a $3 million round for its chips and systems recently and a $20 million round last year.

* Rehnu won $1 million for its unconventional CPV systems design.

Despite the funding activity, CPV is currently a very small piece of the PV pie. In 2011, the leaders in CPV, Amonix, SolFocus and Soitec commissioned 15 megawatts, 5 megawatts and 5 megawatts, respectively. Compare that to the 5 megawatts of photovoltaic panels per day that First Solar was installing on the Agua Caliente project alone. In that light -- even if 2012 is a boom year for potential Solar Junction customers like Amonix, SolFocus, Soitec, and GreenVolts -- CPV remains a small niche market with an underdeveloped supply chain and little economy of scale faced with competition from the still-falling price of flat-panel PV. Amonix does have some large projects due to be commissioned this year, but it remains to be seen if this level of volume can keep CPV cost at par with PV cost.