The influence of sodium on the point defect characteristics in off stoichiometric CuInSe2

Glow discharge optical emission spectrometry for quantitative depth profiling of CIGS thin-films

“…32 Additionally the lattice parameters are dependent on the CGI (CGI ¼ c Cu /(c Ga + c In )), but since this dependency is mostly determined by the formation of Cu-related defects in the crystal structure, there is no generally valid expression derived yet. 33,34 However, for a given CGI the lattice parameters can be derived experimentallyand do not depend on CGI strongly 33,34 in the range usually used for highly efficient CIGSSe solar cells (0.85 < CGI < 0.95). 13 Stephan et al 34 showed that the volume of the unit cell of CISe within that CGI-range is altered by not more than 0.07%.…”

Advanced characterization and in-situ growth monitoring of Cu(In,Ga)Se2 thin films and solar cells

“…These authors found that while in Cu-poor CuInSe 2 , V Cu , Cu In , and In Cu antisite defects are the most frequent ones, the dominant point defects in Cu-poor CuGaSe 2 are Ga i and V Cu . Stephan et al (2016) investigated point defects in CuInSe 2 also in powder obtained by scratching off CuInSe 2 thin films from Mo/ glass substrates. When studying the average neutron scattering lengths of Cu 4a and In 4b sites in CuInSe 2 containing / not containing Na, these authors show that in the presence of Na, Cu-poor CuInSe 2 thin films do not exhibit Cu In antisite defects at high concentrations but rather V In .…”

“…A currently interesting research topic is the investigation of inhomogeneous EBIC and CL signal distributions in Cu(In,Ga)Se 2 thin films when comparing those acquired on adjacent grains (the reader is referred to a recent review on this topic, see reference Abou-Ras et al (2018). These inhomogeneities can limit the open-circuit voltage of the corresponding solar cells (Rau and Werner, 2004) and can be attributed mainly to local fluctuations in the net doping (present probably due to inhomogeneous distributions of charged point defects) and in the lifetime of the electrons (which may be, e.g., affected by inhomogeneous distributions of line or planar defects within grains, which contribute to enhanced recombination) (Stephan et al, 2016). These electrical and optoelectronic analyses on the sub-micrometer scale are correlated with corresponding macroscopic measurements, which are outlined in the following Section.…”

Chalcopyrite compound semiconductors for thin film solar cells

“…In Cu-poor Cu(In,Ga)Se 2 thin films the presence of Na is essential to reach sufficient doping levels [6,80,82]. Neutron diffraction studies show that the addition of Na leads to a decrease of In Cu antisite donors [83], which can explain the increase in p-type doping with the addition of Na. It has been theoretically predicted that while Na is likely to take interstitial sites, K is more likely to go on substitutional sites [84].…”