The enhancement in cell performance of CdTe-based solar cell with Si/SiO 2 distributed Bragg reflectors
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The enhancement in cell performance of CdTe‑based solar cell with Si/ SiO2 distributed Bragg reflectors Yunus Özen1,2 Received: 8 April 2020 / Accepted: 15 July 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract In this study, the very effective design that is Distributed Bragg Reflectors (DBRs) technique and Back Surface Field (BSF) layer are used to fabricate the high-efficiency CdTe-based solar cells. The CdTe-based thin-film solar cells are fabricated as SiO2/Si(DBR)/ZnTe (BSF)/CdTe/CdS/ZnO/FTO. Then, the effects of different number of DBRs layers on CdTe-based solar cell are investigated. 68.77% reflection intensity can be obtained even in 1 period and reflection intensity can reach 99.28% in 3 periods. Significant improvement in cell output parameters are observed with increasing DBRs up to 3 periods. The highest JSC, FF and η values are obtained as 109.82 A/m2, 82.03% and 10.39%, respectively. With the rise in the DBR period, the long wavelength tail of the reflection spectrum is drawn into the center of the reflection band and the long wavelength reflectivity is reduced. This narrowing reduces the rate of reflection of low-energy photons that cannot be absorbed by CdTe layer. Keywords CdS/CdTe · Si/SiO2 · Distributed Bragg reflectors · Thin-film solar cells
1 Introduction The increasing demand for energy needs in the modern world reveals that countries’ sustainable progress directly depends on their energy production rates. Many studies have estimated that the energy consumption in 2050 will be 30 TW for sustainable development of the world [1, 2]. This assumption shows that the need for low-cost, abundant and clean energy sources is very crucial. Hence, the alternative energy sources such as renewable energy sources that do not contain fossil fuels has been very popular. Solar energy can be considered as the best candidate among the renewable energy sources [3–5]. Cadmium telluride (CdTe) is one of the promising absorber layers for inorganic thin-film solar cells due to its efficiency, cost-effectiveness, thermal cell stability and long-term stable performance [6]. CdTe has the high optical absorption coefficient about 5 × 105 cm−1 that gives a chance to use very thin CdTe absorber layer. In addition, CdTe has * Yunus Özen [email protected] 1
Department of Physics, Faculty of Science, Gazi University, 06500 Ankara, Turkey
Photonics Application and Research Center, Gazi University, 06500 Ankara, Turkey
2
a direct optical band gap very close to 1.45 eV, which is the optimum band gap value for solar cells [7]. On the other hand, the wide gap II–VI compounds are used as the window layer for CdTe thin-film solar cells [8–10]. Among these wide gap II–VI compounds, Cadmium sulfide (CdS) is the most suitable n-type hetero-junction partner with p-CdTe absorber layer and affects the cell’s conversion efficiency where thinner CdS films produce higher short-circuit current densities [11]. In this way, the use of CdTe as a thinner absorbing layer can result in less cell materi
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