Double-Sided Heat-Exchange CBD System for Homogeneous Zn(O,S) Thin Films in Highly Efficient CIGS Solar Devices

Abstract

Zn(O,S) thin film as one of the most promising alternative buffer layers in Cu(In,Ga)Se 2 solar devices has drawn considerable attention and been intensively studied in recent years. However, the reliability of the fabrication process still impeded its industrial application. In this work, a self-designed double-sided heat-exchange chemical bath deposition (CBD) system was introduced to deposit large-area homogeneous Zn(O,S) thin films. Compared with the traditional CBD setup, the self-designed system possesses several advantages including fast heat-up, homogeneous heating, wide adaptability, and cost-saving. Intriguingly, based on the self-designed system, high-quality Zn(O,S) thin films with less amounts of OH − and O 2− impurities were easily and successfully deposited without changing the recipe. Furthermore, we have also demonstrated the homogeneity of the solar cells made from the same substrate with a large area and adopted this technique for the fabrication of modules both in the laboratory and in our partner company Shinetech Co., Ltd. As a preliminary result, over 16% conversion efficiency for rigid modules (53 cm 2 ) and over 10% for flexible modules (36 cm 2 ) based on the self-designed deposition system were obtained. As a consequence, a deeper understanding may be provided to deposit high-quality and large-scale Zn(O,S) thin films and hopefully also applicable to industrial.

Study on the Performance of Oxygen-Rich Zn(O,S) Buffers Fabricated by Sputtering Deposition and Zn(O,S)/Cu(In,Ga)(S,Se)2 Interfaces

“…The O-I state (purple lines) located at nearly 530 eV correlates to Zn− O bonding in the lattice oxygen site, and the high binding energy shoulder at 532 eV ascribed to the O-II state (yellow lines) arises from sulfite or sulfate. 7 It is evident that the area of the O-II peak becomes larger and larger than that of the O-I peak when the oxygen partial pressure increases, which agrees well with the results of the S 2p XPS spectra.…”

“…5 CdS has been the most widely studied and used buffer layer in conventional high-efficiency CIGSSe solar cells, but CdS would be a potential threat to the environment and health. 6,7 In the past few decades, many researchers have shown intense interest in developing environmentally friendly buffer layers alternative to CdS. Zinc-based semiconductors are vital alternative candidates, including ZnS, 8 Zn(O,S), 5,9,10 and ZnMgO.…”

“…The Cu­(In,Ga)­(S,Se) 2 (CIGSSe)-based solar cell has long been considered one of the most promising renewable energy technologies due to its excellent photoelectric performance, potentially low cost, and great flexibility for mass production. − The highest efficiency of the CIGSSe solar cell reached to date has been 23.35% . CdS has been the most widely studied and used buffer layer in conventional high-efficiency CIGSSe solar cells, but CdS would be a potential threat to the environment and health. , In the past few decades, many researchers have shown intense interest in developing environmentally friendly buffer layers alternative to CdS. Zinc-based semiconductors are vital alternative candidates, including ZnS, Zn­(O,S), ,, and ZnMgO .…”

Surface Engineering of Submicron Cu(In,Ga)Se2for High-Efficient Zn(O,S)-Based Solar Cells with Lower Light Soaking Effects

“…As for other buffer layers, the results are not as satisfactory as that of the above, that is, 22.0% for the CIGSSe/ZnMgO, 18.2% for the CIGS/ZnSnO, and 16.2% for the CIGS/InS . As described by the literature, there are multiple methods to prepare Zn­(O,S) films, including chemical bath deposition (CBD), ,− atomic layer deposition (ALD), − and the sputtering method. , Moreover, due to the difference between the band structure of Zn­(O,S) and CdS, ZnMgO (see Figure a) is generally used as the subsequent window layer to match with Zn­(O,S) instead of I–ZnO used on CdS.…”

“…On the other hand, the band gap of CdS is narrow, that is, only 2.4 eV which may absorb the photons with a wavelength of less than 520 nm, thereby affecting the performance of the final devices. In view of this, as mentioned above, various environmentally friendly buffer layers have been developed to substitute CdS, including Zn­(O,S), ,,− ZnMgO, − ZnSnO, InS, , and so forth. Among them, Zn­(O,S) has been proved to be the most successful alternative buffer layer with many advantages, such as a simple synthesis approach, high transmittance, and tunable band gap ranging from 2.6 to 3.6 eV based on the alternating of the oxygen-to-sulfur ratio, without causing loss of light absorption in the short-wavelength region .…”