III-V Multijunction solar cells
The main objective of this line is developing high efficiency multijunction solar cells. The focus is put on using III-V materials to achieve this, as they have proven their potential in attaining the highest efficiencies and approaching the physical limits of photovoltaic conversion. Their development to continue pushing the conversion efficiency up involves covering a number of topics, including semiconductor structure fabrication and characterization, solar cell device processing and performance measurement, development of sophisticated measurement techniques, reliability testing, etc.
The two main applications of high efficiency III-V multijunction solar cells are space power and terrestrial concentrator systems. While both applications share the core of most of the research lines mentioned above, they exhibit significant differences. For example, radiation resistance is important only for space power applications, while optimizing the solar cell for operation under non-uniform light spots or under continuously changing spectra is of (central) interest only in the case of terrestrial concentrator systems.
While efficiency is important, cost is also of central importance in photovoltaics, most importantly for utility power generation applications. One of the main research lines is the development of multijunction solar cells based on III-V structures grown on silicon substrates. This aims to take advantage of the mature and low cost silicon technology and at the same time achieving high efficiency by combining it with the III-V technology.