Performance improvement of Perovskite/CZTS tandem solar cell using low-cost ZnS/Ag/ITO multilayer spectrum splitter

https://doi.org/10.1016/j.spmi.2020.106727Get rights and content

Highlights

  • A new approach is proposed to design an efficient low-cost spectrum splitter for tandem solar cell applications.

  • ZnS/Ag/ITO multilayered structure offers 92% of transparency, 89% of reflectance and cut-off wavelength of 700nm.

  • The efficiency of the proposed spectrum is analyzed by implementing it in a perovskite /CZTS tandem cell.

  • The investigated tandem cell exhibits a high efficiency exceeding 16%.

Abstract

In this paper, a new approach based on strategic combination between Dielectric1/Metal/Dielectric2 multilayer aspect and Particle Swarm Optimization (PSO) technique is proposed to design an efficient low-cost spectrum splitter for tandem solar cell applications. This approach allows selecting the suitable dielectric materials, noble metal and geometry of each sub-layer, providing high transparency, while maintaining a superior reflectance within well selected spectral ranges. It is revealed that the optimized ZnS/Ag/ITO multilayered structure offers 92% of transparency and a high reflectance of 89% with an optimum cut-off wavelength of 700 nm. These outstanding results are mainly attributed to the role of the adopted PSO approach in promoting an enhanced light-management. Subsequently, the influence of the optimized spectrum splitter on the solar cell efficiency is analyzed by implementing it in a Perovskite/CZTS tandem cell. It is found that the investigated cell exhibits a high efficiency exceeding 16%, far surpassing that of the conventional monolithic tandem photovoltaic device. This is due to the reduced optical and recombination losses enabled by the use of an optimized and low-cost spectrum splitter system. Therefore, the proposed strategy based on combined Dielectric1/Metal/Dielectric2 spectrum splitting and PSO metaheuristic technique pinpoints a new pathway towards reaching improved efficiencies, making it potential alternative for designing high-efficiency and cost-effective thin-film tandem solar cells.

Introduction

After decades of steady development of photovoltaic energy, Perovskite Solar Cells (PSCs) have received an enormous deal of attention since the 3.8% power conversion efficiency achieved by Japanese research group of Tsutomu Miyasaka in 2009 until reaching a certified efficiency of 25.2% in 2019 [[1], [2], [3], [4]]. Surpassing this value requires avoiding all forms of recombination and optical losses, while maintaining perfect carrier collection efficiency [[2], [3], [4], [5]]. Great efforts in establishing the groundwork of this path have demonstrated that higher efficiencies far surpassing the detailed balance limit of single-junction solar cells (31%) are theoretically achievable using multijunction technologies [[5], [6], [7]]. In this context, several perovskite-based tandem configurations are proposed to achieve broadband absorption over the solar spectrum using wide band-gap (1.6-1.8 eV) perovskite top cell, stacked on different thin-film bottom SCs based on CZTS, silicon and CIGS materials [[5], [6], [7], [8], [9], [10], [11]]. These tandem designs can be either monolithically series-connected or mechanically with four-terminal configuration. Six years ago, the first perovskite-based tandem solar cell in which the bottom cell is based on kesterite material was successfully realized with a low efficiency of 4.6% [11]. Although the fact that the CZTS material optical and electrical properties make it a perfect low-cost tandem partner for PSCs, several undesired effects such as current matching requirement, degradation related to lattice mismatching effects, refractive index differences, interface recombination effects, thermalization and optical losses prevent recording higher efficiencies [[11], [12], [13], [14]].

While searching for more plausible and suitable approaches to enhance the Perovskite/CZTS tandem solar cell power efficiency, we came across a fascinating technology of spectrum splitting systems. Several beam splitting systems have been investigated according to the potential application such as dichroic coating, luminescence solar concentrator and prismatic lens [[14], [15], [16], [17], [18], [19], [20]]. The dichroic filter with multilayer dielectric is the most commonly used splitter design for photovoltaic application and hybrid systems. However, it is still costly, sophisticated and time consuming to elaborate efficient splitter systems that can split the sun-light with an appropriate cut-off wavelength and sloped transition from reflection to transmission [21]. Even though some dichroic coating demonstrated efficient light-splitter systems, that can fit the requirements of tandem photovoltaic devices, they either required high-cost process involving the deposition of large number of interference films or exhibited a non-ideal cut-off wavelength, which can degrade the solar cell efficiency [[21], [22], [23], [24]]. In this perspective, it is believed that the number of the interference layers should be highly reduced, while maintaining an appropriate cut-off wavelength and sloped transition. Accordingly, several simple tri-layer-based spectrum splitting structures were proposed for solar-thermal hybrid systems showing a great promise in achieving high energy harvesting efficiency [25,26]. However, their cut-off wavelength is considered inappropriate for dual-junction SC applications. Moreover, severe reflection losses could affect the solar cell optical behavior, resulting in degrading the conversion efficiency. To the best of our knowledge, no investigations based on a strategic combination between PSO-metaheuristic technique and Dielectric1/Metal/Dielectric2 multilayer spectrum splitter were proposed to outperform the Perovskite-based tandem SCs efficiency. In this context, Dielectric1/Metal/Dielectric2 tri-layered design with 380–700 nm transmission band and 720–1200 nm reflection range is successfully designed. It is found that the optimized ZnS/Ag/ITO multilayer spectrum-splitter structure exhibits 92% of transparency and a high reflectance of 89% with an optimum cut-off wavelength of 700 nm, which has led to record a high-efficiency of 16.2%, far surpassing that of the monolithic tandem counterpart. Therefore, the proposed strategy based on combined multilayer and PSO metaheuristic technique is absolutely useful not only for designing high-efficiency tandem SCs, but also for implementation in software device simulators, in order to optimize several multi-junction designs using efficient and cost-effective spectrum splitting systems.

Section snippets

Modeling methodology and design approach

In this section, we have versatile objectives mainly represented by two-stage investigation frameworks of a new spectrum splitter design based on Dielectric1/Metal/Dielectric2 tri-layered structure for dual-junction solar cell applications. The first objective involves the accurate modeling the optical behavior associated with the analyzed tri-layered beam splitter, while the second goal focuses on describing the systematic optimization approach based on PSO metaheuristic technique used to

Results and discussion

After performing the optimization procedure, Fig. 3 (a) illustrates the evolution of the fitness function versus the number of PSO generation. It can be observed from this figure that an excellent stabilization is achieved for 500 generations and the objective function is appropriately maximized, confirming the effectiveness of the proposed approach for designing efficient light-splitter based on low-cost Dielectric1/Metal/Dielectric2 tri-layered structure. As a result, the optimized

Conclusion

In summary, a new efficient and low-cost spectrum splitting system based on Dielectric1/Metal/Dielectric2 multilayer structure is designed using an effective approach based on PSO global optimization. The optimization approach revealed that ZnS/Ag/ITO tri-layer could behave like an efficient optical filter with appropriate cut-off wavelength, where a high transparency of 92% is reached in the spectrum band of [380 nm-700nm] and a superior reflectance of 89% is achieved over the spectral range

Credit author statement

H. Ferhati: Writing - original draft, Software, Validation. F. DJEFFAL: Conceptualization, Methodology, Writing- Reviewing and Editing, Supervision, Validation. B.L. Drissi: Writing- Reviewing and Editing.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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