Review on Substrate and Molybdenum Back Contact in CIGS Thin Film Solar Cell

Abstract

Copper Indium Gallium Selenide- (CIGS-) based solar cells have become one of the most promising candidates among the thin film technologies for solar power generation. The current record efficiency of CIGS has reached 22.6% which is comparable to the crystalline silicon- (c-Si-) based solar cells. However, material properties and efficiency on small area devices are crucial aspects to be considered before manufacturing into large scale. The process for each layer of the CIGS solar cells, including the type of substrate used and deposition condition for the molybdenum back contact, will give a direct impact to the efficiency of the fabricated device. In this paper, brief introduction on the production, efficiency, etc. of a-Si, CdTe, and CIGS thin film solar cells and c-Si solar cells are first reviewed, followed by the recent progress of substrates. Different deposition techniques’ influence on the properties of molybdenum back contact for CIGS are discussed. Then, the formation and thickness influence factors of the interfacial MoSe2 layer are reviewed; its role in forming ohmic contact, possible detrimental effects, and characterization of the barrier layers are specified. Scale-up challenges/issues of CIGS module production are also presented to give an insight into commercializing CIGS solar cells.

Modifications of the CZTSe/Mo back-contact interface by plasma treatments

“…For the Mo/TiN/Mo case, in which no direct contact of TiN with the CZTSe absorber exists, the negative impact of TiN is largely eliminated, and the resulting CZTSe/MoSe 2 interface may lead to improved electronic properties. 2,13 The solar cells based on this conguration perform more closely (i.e., mainly 8-9% efficiency) to the devices without an extra back-contact barrier discussed above. However, the results do not indicate any improvement of the device properties for reducing the MoSe 2 layer thickness from z1 mm range down to less than 250 nm.…”

“…Mo has been proven to be an appropriate back-contact material in CIGS technologies. [1][2][3][4][5][6] Due to the similar device structure to CIGS solar cells, Mo is also widely used as a backcontact material for CZTSe solar cells. 7,8 Due to the high temperature annealing process, uncontrolled formation of an interfacial MoSe 2 layer with a thickness ranging from a few tens of nm up to z1 mm is commonly observed in most fabrication methods.…”

“…12 MoSe 2 is considered to have the advantages of improving adhesion and lowering the existing potential barrier at the back-contact interface. 2,13 However, a too thick MoSe 2 interfacial layer can cause additional series resistance and mechanical instability in the device structure. Consequently, the suppression or the control of MoSe 2 formation appears to be a useful approach for improving the overall quality of the back contact and its interface with the absorber.…”

“…Such a nitrided Mo surface was discussed in literature to possibly have benecial effects on interface stability and quality in thin-lm CIGS solar cells. 2,20 Finally, as comparison, we combine the Ar plasma treatment with the application of TiN back-contact barrier, which was demonstrated as a possible Se barrier in literature. 15,16 We discuss our results in terms of MoSe 2 thickness, thickness homogeneity and resulting solar cell performance.…”

Effects of Annealing on Characteristics of Cu2ZnSnSe4/CH3NH3PbI3/ZnS/IZO Nanostructures for Enhanced Photovoltaic Solar Cells

“…The actual PV devices involved frames, glasses, and other compound materials, which could further challenge the recycling scheme [16]. In addition, metal-selenide had been studied as a carrier-transporting material in perovskite by various sputtering techniques [17][18][19]. This paper has focused on applyingCu 2 ZnSnSe 4 as HTM nano-film, and fabricated by innovative concept to improve Cu-based PV performance.…”