Morphological and Structural Changes in Cu(In,Ga)Se₂ Thin Films by Selenization Using Diethylselenide

Abstract

The morphological and structural changes in Cu(In,Ga)Se2 (CIGS) thin films during selenization using diethylselenide (DESe) are investigated. The surface morphology and extra phase existence of CIGS thin films strongly depend on the heating profile temperature and time of each step during selenization. Conventional high-temperature (515 °C) selenized CIGS thin films formed grains of approximately 2–3 µm, although the Cu–In–Ga metallic precursor was very smooth. On the other hand, the precursor selenized at a low temperature (about 400 °C) exhibited a homogeneous surface morphology because the precursor was formed from Cu–Se and (In,Ga)–Se alloys to diffuse selenide into a Cu–In–Ga metallic precursor. The high-temperature selenized CIGS thin films after low-temperature selenization had a homogeneous surface morphology with appropriate-sized grains. These results indicate that the heating profile “during” selenization was very important in forming Cu–Se and (In,Ga)–Se alloys from a Cu–In–Ga metallic precursor.

Growth Conditions and Structural Properties of Cu(In,Ga)Se2 Thin Films Prepared by Selenization Method Using Diethylselenide

“…Such large-grain growth is related to the liquid-phase growth of CIGS with the aid of Cu x Se flux. 22) This is because Cu-Se flux growth occurs during selenization, 2,8,[23][24][25][26] and large grains with (112) facets are formed at a high selenization temperature of 540 C.…”

“…Recently, diethylselenide (DESe) has been studied as a new selenium source for the selenization of CuInSe 2 (CIS) 4,5) and CIGS. [6][7][8][9] It is liquid at room temperature (RT) and known to be a metalorganic selenide having a higher safety than H 2 Se gas. Its higher decomposition efficiency than H 2 Se makes it cost-effective.…”

“…4,5) The structural properties of selenized CIGS thin films have been reported. [6][7][8] A solar cell with a high efficiency of 13.7% has been demonstrated using Cu(In,Ga)(Se,S) 2 (CIGSeS) absorber films prepared by selenization using DESe. 9) However, the detailed preparation conditions for the formation mechanism of the selenization process using metalorganic selenides have not yet been fully understood.…”

Microstructrual evolution of all-wet-processed CIGS films using Raman spectroscopy

“…CIGS solar cells are multilayer devices, and there are two primary techniques for making the intermediate CIGS layer. One of these techniques is the multisource evaporation method, which was used in the production of the highest conversion efficiency CIGS cells yet known . Despite the obvious advantage of this technique, the high production costs, limitations on sample size, and chamber‐contamination problems of multisource evaporation make it problematic for widespread use.…”

Control of Grain in Cu(In,Ga)Se2 Thin Films Prepared by Selenization Method Using Diethylselenide

“…Recently, DESe has been studied as a source for the selenization method of CuInSe 2 (CIS) and CIGS thin films. [3][4][5][6][7][8] Preparation of polycrystalline CIS 3,4) and CIGS [5][6][7] films using DESe has been reported, and the films exhibited densely-packed, single-phase, and good adhesive property. A high efficiency Cu(In,Ga)(SeS) 2 solar cell with conversion efficiency of 13.7% has been realized by means of the selenization method using DESe.…”