Spray-Ion Layer Gas Reaction (ILGAR)a Novel Low-Cost Process for the Deposition of Chalcopyrite Layers up to the Micrometer Range for Photovoltaic Applications

Abstract

A novel variant of the ion layer gas reaction (ILGAR) process is described. Up to now, only layers with a maximum thickness of about 100 nm could be deposited by ILGAR in a reasonable time. Replacing of dipping by spraying on a warm substrate accelerated the application of the precursor solution (e.g., metal chloride in water) by a factor of at least 100. For multinary products, all precursors are applied either simultaneously as a mixed solution or sequentially. In intervals, the spraying is stopped and the reaction gas H 2 S is allowed to flow over the substrate. A special, yet simple setup is shown, which allows also a recycling of unconverted precursor. In about an hour time, a micrometer thick layer of mixed or stacked CuS/In 2 S 3 /(Ga 2 S 3 ) (from CuCl 2 , InCl 3 and in some cases GaCl 3 , respectively) is deposited. The latter is converted to CuInS 2 (CIS) or Cu(In,Ga)S 2 (CIGS) by annealing in H 2 S/Ar at 550 °C. The thermodynamically stable product distribution for this process is calculated. The influence of the process parameters, substrate temperature during precursor deposition, annealing temperature, CuCl 2 /InCl 3 ratio and gallium addition, is studied. The layers are used as absorbers in chalcopyrite thin film solar devices. The grain size necessary for this purpose is already sufficient (ca. 0.5-0.7 µm diameter). First solar cells based on spray-ILGAR-CIS and -CIGS have been prepared and compared. The efficiency has already reached 3.4%. An unusual layer morphology is obtained when the substrate temperature is too high (>90 °C). In this case, the layer consists of ideal hollow spheres with a hole in them. An explanation for this phenomenon is given.

Preparation of Titania on Stainless Steel by the Spray-ILGAR Technique as Active Photocatalyst under UV Light Irradiation for the Decomposition of Acetaldehyde

“…This shows that the thickness of the TiO 2 film on stainless steel was only influenced by the spraying time, and not so much by the concentration of the TiO 2 precursor and heating temperature. This is in accordance with the findings of Fischer et al [8] where they reported that a reasonable time of deposition by ILGAR is needed in order to obtain layers with a maximum thickness of about 100 nm.…”

“…When the spraying duration was shortened to 6 min, some parts of the stainless steel were uncoated by the TiO2 (Figure 3a). This is most probably caused by insufficient spraying time for the layer to form [8]. The thickness measurement also supports this hypothesis.…”

“…This is most probably caused by insufficient spraying time for the layer to form [8]. The thickness measurement also supports this hypothesis.…”

“…Spray-ILGAR is an extension of the ion layer gas reaction (ILGAR) technique, which was developed and patented by the group of Professor Dr. Christian-Herbert Fischer at the Helmholtz-Zentrum Berlin for Materials and Energy, in Berlin, Germany [8], and which is equivalent to the aerosol assisted chemical vapour depostition (AACVD) method [9]. ILGAR is a non-vacuum, thin-film deposition technique, involving a sequential and cyclic process that enables the deposition of semiconductor thin films, especially chalcopyrite absorber layers and buffer layers.…”

Covellite CuS – Single crystal growth by chemical vapour transport (CVT) technique and characterization

“…Numerous research papers reporting synthesis of CuS in thin films [8][9][10][11][12][13][14][15][16][17][18], nanoparticles [19][20][21][22][23][24][25][26][27][28][29][30], micro-meter size morphologies [31,32], etc. forms have been reported.…”