Influence of high growth rates on evaporated Cu(In,Ga)Se₂ layers and solar cells

Abstract

Thin film solar cells based on polycrystalline Cu(In,Ga)Se2 were prepared by elemental co‐evaporation using modified three‐stage processes on soda lime glass substrates at a low substrate temperature of 450°C intended for application on polyimide foils. The growth rates in the different stages of the growth process were varied, and it was observed that the final composition profile and structural quality of the film are mainly determined by the growth rate in the third stage. Application of high growth rates in the second stage was found to have no significant impact on layer morphology and gallium grading profile, which was confirmed by scanning electron microscopy, secondary ion mass spectroscopy, and x‐ray diffraction measurements. On the other hand, scanning electron microscopy cross sections revealed that high growth rates in the third stage lead to a fine‐grained structure toward the surface as well as smaller grains toward the back contact. Secondary ion mass spectroscopy and x‐ray diffraction measurements of such layers revealed a pronounced gallium grading profile, while Raman spectroscopy showed strong occurrence of group III‐rich phases in the near‐surface region. The final device performance was found to deteriorate by about 10% relative to the baseline process efficiency when growth rates of up to 500 nm min−1 were applied in the second stage or 600 nm min−1 in the third stage. Copyright © 2011 John Wiley & Sons, Ltd.

Synthesis of CuIn<I><SUB>1-x</SUB></I>Ga<I><SUB>x</SUB></I>Se<SUB>2</SUB> Nanoparticles by Thermal Decomposition Method with Tunable Ga Content

“…All the samples showed the prominent peak corresponding to the A 1 optical phonon vibrational mode of chalcopyrite crystal structure. 24 As Ga content increases, the peak position is shifted to higher wavenumber. The same behavior was found by Olejnicek et al 19 Figures 5(a)-(e) shows FE-SEM micrographs of the synthesized CIGS nanoparticles with varying x values from 0 to 1.…”

Cu(In,Ga)Se2 solar cell grown on flexible polymer substrate with efficiency exceeding 17%

“…The main process parameters investigated in this work which determine the overall grading profile are (i) the deposition rate in the 3rd stage which was reduced significantly and (ii) the amount of Cu‐excess reached at the end of the 2nd stage, which was increased from 10 to about 15%. Previous work on low‐temperature grown CIGS has shown that increasing the growth rate in the 3rd stage leads to a much more pronounced grading profile near the surface as well as to significantly hindered crystallization 12, 13. Therefore, the deposition rate in the 3rd stage was reduced to enhance the structural quality of the CIGS film.…”

Electronic properties of Cu(In,Ga)Se2 solar cells on stainless steel foils without diffusion barrier

“…In a next step, CIGS was deposited by co‐evaporation of Cu, In, Ga, Se elements with a modified three‐stage process. The details of the deposition process are given elsewhere . Two different nominal maximum substrate temperatures of 475°C (LT) and 600°C (HT) were used.…”