In this paper we present the current status of modelling the time evolution of the transient conductivity of photoexcited semi-insulating (SI) 4H–SiC taking into account the properties of defect centres. A comprehensive model that includes the presence of six, the most significant, point defects occurring in SI 4H–SiC crystals is presented. The defect centres are attributed to the two kinds of nitrogen-related shallow donors, a boron-related shallow acceptor, deep electron and hole traps, and the Z_1/2 recombination centre. We present the results of the state-of-the-art numerical simulations showing how the photoconductivity transients change in time and how these changes are affected by the properties of defect centres. The properties of defect centres assumed for modelling are compared with the results of experimental studies of deep-level defects in high purity (HP) SI 4H–SiC wafers performed by the high-resolution photoinduced transient spectroscopy (HRPITS). The simulated photoconductivity transients are also compared with the experimental photocurrent transients for the HP SI 4H–SiC wafers with different deep-level defects. It is shown that a high-temperature annealing producing the C-rich material enables the fast photocurrent transients to be achieved. The presented analysis can be useful for technology of SI 4H–SiC high-power photoconductive switches with suitable characteristics.

Photovoltaic (PV) technologies which play a role in PV market are divided into basic two types: wafer-based (1st generation PV) and thin-film cell (2nd generation PV). To the first category belong mainly crystalline silicon (c-Si) cells (both mono- and multi-crystalline). In 2015 around 90% of the solar market belonged to crystalline silicon. To the 2nd generation solar cells belongs thin film amorphous silicon (a-Si) or a combination of amorphous and microcrystalline silicon (a-Si/μc-Si), compound semiconductor cadmium telluride (CdTe), compound semiconductor made of copper, indium, gallium and selenium (CIS or CIGS) and III–V materials. The PV market for thin film technology is dominated by CdTe and CIGS solar cells. Thin film solar cells’ share for all thin film technologies was only 10% in 2015. New emerging technologies, called 3rd generation solar cells, remain the subject of extensive R&D studies but have not been used in the PV market, so far.

In this review the best laboratory 1st and 2nd generation solar cells that were recently achieved are described. The scheme of the layer structure and energy band diagrams will be analyzed in order to explain the boost of their efficiency with reference to the earlier standard designs.