Solid solution, lattice parameter values, and effects of electronegativity in the (Cu1−xAgx)(Ga1−yIny)(Se1−z Tez)2 alloys

Abstract

Equilibrium conditions for the alloy system (CUI _ xAgx)(Gal _ylny)(Se l _ z Tezb were determined throughout the complete range of composition. Polycrystalline samples of 125 different compositions, i.e., with x,y, and z = 0, 0.25, 0.5, 0.75, and l.0, were prepared by a melt and anneal technique. Different annealing temperatures in the range 6@..800 ·C were used depending upon the alloy composition and annealing times of up to 5 months used to attain equilibrium conditions. Debye-Scherrer x-ray powder photographs were used to investigate the equilibrium conditions. It was found that single phase chalcopyrite structure was obtained for all compositions of the copper (x = 0), indium ( y = 1), and tellurium (z = 1) sections but that miscibility gaps occurred in the silver (x = 1), gallium (y = 0), and selenium (z = 0) sections, and that these miscibility gaps extended through the general alloy system. Values oflattice parameters a and c were determined for all samples showing single phase condition and for each of the above sections the variations of a and c with composition were fitted to power series in the appropriate composition coordinates. Hence contours of constant a and constant c were determined. From the parameters for each section, general series expressions in x, y, and z were developed and the values from these compared with the experimental data for the general alloys. It is shown that a modified Weaire and Noolandi relation of the form [2 -(c/a)] = K (XI -XIII + qX VI f fits all of the experimental data. Averaged values of K and q were obtained by fitting separately to different sections of the alloy system and also to all alloys of the complete system.

Characterization and device performance of (AgCu)(InGa)Se<inf>2</inf> absorber layers

“…2) to survey phase behavior, optical properties [4], and device performance. XRD analysis in the present study, in contrast to the earlier work of Avon [1], indicated little evidence of chalcopyrite phase segregation. For example, a film deposited with composition Ag/(Ag+Cu) = 0.46 and Ga/(In+Ga) = 0.50, near the center of the two-phase region reported by Avon et al, showed no evidence of phase segregation as shown by the XRD (112) peak profile in Fig.…”

“…These results are noteworthy, however, in that they demonstrate a high tolerance to Ag incorporation from a device standpoint. No obvious evidence of phase segregation is observed in contrast to earlier reports [1].…”

“…The phase behavior of the (AgCu)(InGa)(TeSe)2 system has been previously studied by Avon et al [1] A miscibility gap was observed by x-ray diffraction (XRD) analysis of ampoule-synthesized (AgCu)(InGa)Se2 ingots in the approximate composition window 0.25 < Ag/(Ag+Cu) < 0.75 and 0.25 < Ga/(In+Ga) < 1.0. [1] From a device standpoint, a noteworthy result in the Ag(InGa)Se2 system is the work of Nakada et al who achieved a device with VOC = 949 mV, JSC = 17.0 mA/cm 2 , FF = 58%, and η = 9.3% using an Ag(In0.2Ga0.8)Se2 absorber layer.…”

“…[1] From a device standpoint, a noteworthy result in the Ag(InGa)Se2 system is the work of Nakada et al who achieved a device with VOC = 949 mV, JSC = 17.0 mA/cm 2 , FF = 58%, and η = 9.3% using an Ag(In0.2Ga0.8)Se2 absorber layer. [2] The present study includes results for solar cells spanning nearly the complete (AgCu)(InGa)Se2 pentenary system.…”

Optical and quantum efficiency analysis of (Ag,Cu)(In,Ga)Se<inf>2</inf> absorber layers

“…This work expands upon this in determining the bandgaps and the bowing parameters for a wider range of compositions of (Ag,Cu)(In,Ga)Se2 thin films. Supplementary work by Avon, et al [5] on the same (Ag,Cu)(In,Ga)Se2 ampoule-synthesized-ingot-based samples also reported a chalcopyrite-chalcopyrite immiscibility gap for certain bulk compositions. X-ray diffraction (XRD) studies of the thin films studied here showed a single phase throughout the alloy compositional system.…”