Improving Performance of CIGS Solar Cells by Annealing ITO Thin Films Electrodes

Chuan Lung Chuang,Chung Ping Liu,Nien Po Chen,Ming Wei Chang,Chung Chiang Pan

doi:10.1155/2015/483147

Abstract

Indium tin oxide (ITO) thin films were grown on glass substrates by direct current (DC) reactive magnetron sputtering at room temperature. Annealing at the optimal temperature can considerably improve the composition, structure, optical properties, and electrical properties of the ITO film. An ITO sample with a favorable crystalline structure was obtained by annealing in fixed oxygen/argon ratio of 0.03 at 400°C for 30 min. The carrier concentration, mobility, resistivity, band gap, transmission in the visible-light region, and transmission in the near-IR regions of the ITO sample were-1.6E+20 cm−3,2.7E+01 cm2/Vs,1.4E-03 Ohm-cm, 3.2 eV, 89.1%, and 94.7%, respectively. Thus, annealing improved the average transmissions (400–1200 nm) of the ITO film by 16.36%. Moreover, annealing a copper-indium-gallium-diselenide (CIGS) solar cell at 400°C for 30 min in air improved its efficiency by 18.75%. The characteristics of annealing ITO films importantly affect the structural, morphological, electrical, and optical properties of ITO films that are used in solar cells.

Highlights

Indium tin oxide (ITO) film has highly favorable properties, such as low resistivity (∼10−4 Ohm-cm), high optical transmittance for visible light, and high near-infrared reflectance, making it effective as an n-type window layer, in solar cells [1, 2]
The X-ray diffraction (XRD) measurements were made by scanning the diffraction angle from 20 to 65∘ at a grazing angle of incidence of 2∘
Samples that were deposited in pure argon exhibited no preferential crystalline orientation, whereas the XRD diffraction patterns of the ITO

Summary

Introduction

Indium tin oxide (ITO) film has highly favorable properties, such as low resistivity (∼10−4 Ohm-cm), high optical transmittance for visible light, and high near-infrared reflectance, making it effective as an n-type window layer, in solar cells [1, 2]. ITO thin films can be prepared using many techniques, including e-beam evaporation [5, 6], plasma-enhanced metal organic chemical vapor deposition [7], pulsed laser deposition [8], dip coating [9], ion beam sputtering [10], magnetron sputtering [11], and thermal evaporation [12]. Among these for forming ITO thin films, magnetron sputtering has the advantage of being able to form films of high quality at room temperature [13,14,15,16], which can be used to coat large areas [17, 18]. Some of the ITO film samples were deposited at room temperature using a fixed oxygen/argon ratio of 0.03 before being annealed at various temperatures (as-grown/100∘C/200∘C/300∘C/400∘C) for 30 min in air

Experimental Method

Results and Discussion

Conclusions