Manipulation of MoSe₂Films on CuIn(Ga)Se₂Solar Cells during Rapid Thermal Process

Abstract

In this study, the CuIn(Ga)Se2(CIGS) crystalline quality and MoSe2thickness of films produced by the rapid thermal selenization process under various selenization pressures were investigated. When the selenization pressure increased from 48 Pa to 1.45 × 104 Pa, the CIGS films were smooth and uniform with large crystals of varying sizes. However, the MoSe2thicknesses increased from 50 nm to 2,109 nm, which created increased contact resistivity for the CIGS/MoSe2/Mo structures. The efficiency of CIGS solar cells could be increased from 1.43% to 4.62% due to improvement in the CIGS crystalline quality with increasing selenization pressure from 48 Pa to 1.02 × 103 Pa. In addition, the CIGS crystalline quality and MoSe2thickness were modified by the pressure released valve (PRV) selenization process method. The crystalline qualities of the CIGS films were similarly affected by the selenization pressure at 1.02 × 103 Pa in the PRV selenization method and the MoSe2thicknesses were reduced from 1,219 nm to 703 nm. A higher efficiency of 5.2% was achieved with the thinner MoSe2obtained by using the PRV selenization method.

Formation of a Mo2N skin layer in columnar-structural Mo films using NH3 plasma nitridation as the Se diffusion-barrier layer

“…3(c) and (d). The thickness of the pure-Mo films increased dramatically from 480 nm to 750 nm due to the volume expansion of MoSe 2 [10][11][12][13][14][15], whereas the n-Mo films remained unchanged after selenization process. This result showed the chemical stability of Mo 2 N layer under the Seenvironment, and the Mo 2 N layer properly acted as the Se diffusion barrier.…”

“…This showed the strong chemical stability of n-Mo films under Se-environment. Thus, problems of MoSe 2 formation in solar cells, such as the contact deterioration between an absorber and Mo film due to volume expansion and the degradation of electrical property, were easily solved by applying n-Mo films [11][12][13][14][15][16][17][18]. Fig.…”

“…On the other hand, absorber growth under high temperature conditions and Se-environments causes the rapid diffusion of Se into the Mo electrode, which results in the formation of a MoSe 2 layer between the CIGS and Mo electrode. A thick MoSe 2 layer exhibits high resistivity (10 1 -10 4 Ω·cm) and volume expansion of Mo because of the formation of MoSe 2 , which can deteriorate the contact properties between CIGS and the Mo electrode [10][11][12][13][14]. Therefore, the formation of MoSe 2 is one of main reasons to decrease the efficiency of solar cells.…”

Obtención de estructuras calcopirita (CIGS) y kesterita (CZTS) como absorbentes para dispositivos fotovoltaicos de capa fina mediante métodos de síntesis de bajo coste

“…Una capa de MoSe 2 con el espesor adecuado actúa como contacto cuasi-óhmico [223] y mejora los valores de V OC [224] del dispositivo debido al efecto de campo de la superficie trasera (Back Surface Field effect, BSF) [88]. Sin embargo, un espesor excesivo trae como consecuencia un aumento de la resistencia en serie (R S ) y disminución en la J SC [225]. Por tanto, menor selenización del Mo en la muestra R5, debido a la menor temperatura empleada (ataque menos agresivo sobre el Mo) da lugar a la formación de un mejor contacto óhmico de MoSe 2 , el cual optimiza el V OC respecto a R2 (0,48 V frente a 0,25 V).…”

Cadmium-free buffer layer for electrochemically deposited chalcopyrite solar cell

“…Bearing this in mind, the high temperature selenization temperature should be as high as possible. However, higher temperature will cause the formation of thicker MoSe2 layer and poor adhesion between CIS and Mo, which are both detrimental to the device performance [88][89][90]. Therefore, the optimal selenization temperature should be compromised taking into account the above factors.…”