Production of single phase chalcopyrite CuInSe2 by spray pyrolysis

Abstract

Thin films (0.5–2 μ) of CuInSe2 were prepared by spray pyrolysis from solutions with various pH levels and initial Cu:In ratios, and in which the Cu source was either CuCl or CuCl2. The substrate temperature was varied between 225 and 300 °C. All films prepared with CuCl2 were chalcopyrite, while only Cu-rich CuCl based films exhibited this phase. The appearance of Cu2−xSe and/or Cu2/Se as a second phase was found to depend strongly on solution stoichiometry, pH, temperature, and substrate. Two layer structures consisting of a Cu-deficient layer on top of a Cu-rich layer were produced without the presence of any second phases on both glass and Mo-coated glass. This is the first time single phase chalcopyrite Cu-deficient layers have been fabricated by spray pyrolysis. A CuInSe2/CdS photovoltaic cell made from a single phase double layer filme on glass gave a Voc of 0.558 V after heat treatment. This Voc is higher than any reported to date. Absorption spectra have also been measured, and are found to improve when CuCl2 is used instead of CuCl.

Preparation and Study of Structural and Optical Properties of Chemical Bath Deposited Copper Indium Diselenide Thin Films

“…The presence of a single slope in the curves suggests that all the films are of single phase in nature and the type of transition is direct and allowed. This type of transition has already been reported by several workers [3,14,28,40,41]. At higher wavelengths the non-linear tail absorption in the curves may be due to transitions associated with absorption of longer wavelength phonons as reported earlier [42].…”

“…CuInSe 2 thin film with a direct band gap of about 1.0 eV [1][2][3] and a large absorption coefficient in the range of 10 4 -10 5 cm --1 [2,4] is one of the promising absorbing materials for heterojunction solar cells. CuInSe 2 thin films have been prepared by various techniques, viz., close-spaced vapour transport [5], electrodeposition [6][7][8][9], three-source evaporation [10], selenization [11], molecular beam deposition [12], spray pyrolysis [13], pulsed excimer laser ablation [14], flash evaporation [15] and chemical bath deposition [16][17][18][19][20].…”

Influence of the stacking order on structural features of the Cu‐In‐Ga‐Se precursors for formation of Cu(In,Ga)Se 2 thin films prepared by thermal reaction of InSe/Cu/GaSe alloys to elemental Se vapor and diethylselenide gas

“…It is therefore reasonable to assume that the surface of the absorber film contains pure CuInSe 2 and that the gallium increases continuously towards the Mo back contact. These observations are in good agreement with other related studies and are attributed to the difference in the formation kinetics of the two ternary phases [4]. On the contrary, the XRD patterns of the films selenized by DESe as shown in Fig.…”

“…A seemingly insurmountable disadvantage of these processes is that the resultant semiconductor absorber films are heterogeneous. Due to the difference in the reaction rates between the binary selenides, the bulk of the material contains discrete CuInSe 2 and CuGaSe 2 phases [4]. Alternatively, graded film structures are obtained with most of the gallium located at the back of the film.…”

Electrochemically Fabricated Alloys and Semiconductors Containing Indium

“…26) Chemical methods for the preparation of thin film alloys include approaches such as chemical vapor deposition, 27,28) chemical bath deposition, 29) electrodeposition, 8,29) and spray pyrolysis. 30,31) Molecular-beam epitaxy (MBE) 32,33) can be a physical or a chemical method, because the beam of materials can be generated by physical means or by chemical reactions. Among the methods used to grow thin alloy films of indium, an electrochemical approach may be superior, because unlike the other methods, it enables up to 98% of the material to be effectively used.…”