CZTSe solar cells prepared by electrodeposition of Cu/Sn/Zn stack layer followed by selenization at low Se pressure

Abstract

Cu2ZnSnSe4 (CZTSe) thin films are prepared by the electrodeposition of stack copper/tin/zinc (Cu/Sn/Zn) precursors, followed by selenization with a tin source at a substrate temperature of 530°C. Three selenization processes were performed herein to study the effects of the source of tin on the quality of CZTSe thin films that are formed at low Se pressure. Much elemental Sn is lost from CZTSe thin films during selenization without a source of tin. The loss of Sn from CZTSe thin films in selenization was suppressed herein using a tin source at 400°C (A2) or 530°C (A3). A copper-poor and zinc-rich CZTSe absorber layer with Cu/Sn, Zn/Sn, Cu/(Zn + Sn), and Zn/(Cu + Zn + Sn) with metallic element ratios of 1.86, 1.24, 0.83, and 0.3, respectively, was obtained in a selenization with a tin source at 530°C. The crystallized CZTSe thin film exhibited an increasingly (112)-preferred orientation at higher tin selenide (SnSe x ) partial pressure. The lack of any obvious Mo-Se phase-related diffraction peaks in the X-ray diffraction (XRD) diffraction patterns may have arisen from the low Se pressure in the selenization processes. The scanning electron microscope (SEM) images reveal a compact surface morphology and a moderate grain size. CZTSe solar cells with an efficiency of 4.81% were produced by the low-cost fabrication process that is elucidated herein.

Reactive Mechanism of Cu2ZnSnSe4 Thin Films Prepared by Reactive Annealing of the Cu/Zn Metal Layer in a SnSex + Se Atmosphere

“…The typical deposition time was about 15 seconds. Samples of the metallic precursors (4 cm 2 × 4 cm 2 in area) were reactively annealed in a laboratory-made furnace capable of working in vacuum (1 × 10 −4 Pa) or an inert gas (Ar) atmosphere [13]. The sample temperature, Sn temperature and the Se temperature are controlled individually.…”

“…Their values are still far from the record cell efficiency of above 21% for Cu(In,Ga)Se 2 [4] and CdTe [5]. Because of the thermodynamic stability of CZTS(e) thin films [6] and the volatility of tin selenide (SnSe x ) [7], a two-step process was generally used to prepare CZTSe thin films [2,3,[7][8][9][10][11][12][13]. A precursor with all or part of the CZTS(e) components was prepared first by either a vacuum or non-vacuum method and was then treated by subsequent thermal annealing to improve the crystallinity.…”

Effect of Sn Content in a CuSnZn Metal Precursor on Formation of MoSe2 Film during Selenization in Se+SnSe Vapor

“…The Gibbs free energy changes of the two reactions are negative, implying that both of the chemical reactions may occur spontaneously. However, in our previous study [22], the formation of MoSe 2 layer is very slow when the selenization of metal precursor is at a low Se partial pressure atmosphere. Therefore, we can conclude that the formation of the MoSe 2 layer in sample A3 is dominated by the reaction of 2SnSe 2 + Mo = 2SnSe + MoSe 2 , owing to the excess of SnSe x from the reactions of Cu x Sn y + 2Se x (g) → Cu 2− x Se + SnSe x during selenization.…”

“…Samples of the metallic precursors were reactively selenized in a laboratory-made furnace (not a tubular furnace) capable of working in vacuum (10 −4 Pa) or an inert gas (Ar) atmosphere [22]. The sample temperature, Sn temperature and the Se temperature are controlled individually.…”

Solution-Processed Cu2ZnSn(S,Se)4 Thin-Film Solar Cells Using Elemental Cu, Zn, Sn, S, and Se Powders as Source

“…Recently, various approaches have been developed to fabricate the absorber layers, briefly including vacuumbased deposition and non-vacuum-based solution process; both strategies have yielded a remarkable improvement in photovoltaic performance [2][3][4][5][6][7][8]. Compared to vacuumbased approaches, non-vacuum technologies such as electrodeposition approach [9][10][11], milling dispersion approach [12], nanoparticle-based approach [13][14][15][16], hydrazine-based approach [17][18][19], and sol-gel approach [20][21][22][23][24] are more feasible for industrial production. Among those solution-based process, the hydrazine-based deposition has made the great progress, achieving the power conversion efficiency (PCE) of 12.6 % [25].…”