• Ceramist
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• v.22 no.2
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• pp.146-169
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• 2019

To overcome the theoretical efficiency of single-junction solar cells (> 30 %), tandem solar cells (or multi-junction solar cells) is considered as a strong nominee because of their excellent light utilization. Organic-inorganic halide perovskite has been regarded as a promising candidate material for next-generation tandem solar cell due to not only their excellent optoelectronic properties but also their bandgap-tune-ability and low-temperature process-possibility. As a result, they have been adopted either as a wide-bandgap top cell combined with narrow-bandgap silicon or CuIn_xGa_(1-x)Se₂ bottom cells or for all-perovskite tandem solar cells using narrow- and wide-bandgap perovskites. To successfully transition perovskite materials from for single junction to tandem, substantial efforts need to focus on fabricating the high quality wide- and narrow-bandgap perovskite materials and semi-transparent electrode/recombination layer. In this paper, we present an overview of the current research and our outlook regarding perovskite-based tandem solar technology. Several key challenges discussed are: 1) a wide-bandgap perovskite for top-cell in multi-junction tandem solar cells; 2) a narrow-bandgap perovskite for bottom-cell in all-perovskite tandem solar cells, and 3) suitable semi-transparent conducting layer for efficient electrode or recombination layer in tandem solar cells.

• Current Photovoltaic Research
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• v.12 no.3
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• pp.61-73
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• 2024

All-perovskite tandem solar cells have been developed as a next-generation solar cell technology to surpass the efficiency limits of single-junction solar cells. By using perovskite materials with different bandgaps in the top and bottom cells, these tandem solar cells can effectively utilize a wider range of the solar spectrum. All-perovskite tandem solar cells have been focused as a next-generation solar cell due to their ability to achieve high efficiency while being manufactured through low-cost solution processing. This paper focuses on key components for improving the performance of all-perovskite tandem solar cells and essential components: wide bandgap perovskite solar cells, narrow bandgap perovskite solar cells, and charge recombination layers. The characteristics, main challenges, and strategies for overcoming these issues are discussed. For wide bandgap perovskites, efficiency is reduced by high trap densities and halide ion phase segregation. Improvement methods through additives and surface passivation are proposed to overcome these issues. In narrow bandgap perovskites, composition control and surface treatment techniques are being developed to reduce the oxidation of Sn-based materials and charge recombination in the perovskite. Additionally, the charge recombination layer is an essential component for efficient electron-hole recombination and minimizing optical losses, with materials such as transparent conductive oxides and ultrathin metals being used. These studies make a significant contribution to enhancing the efficiency and stability of all-perovskite tandem solar cells and suggest future research directions for commercialization.

• Korean Journal of Materials Research
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• v.33 no.8
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• pp.344-351
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• 2023

Cesium lead iodide (CsPbI₃) with a bandgap of ~1.7 eV is an attractive material for use as a wide-gap perovskite in tandem perovskite solar cells due to its single halide component, which is capable of inhibiting halide segregation. However, phase transition into a photo inactive δ-CsPbI₃ at room temperature significantly hinders performance and stability. Thus, maintaining the photo-active phase is a key challenge because it determines the reliability of the tandem device. The dimethylammonium (DMA)-facilitated CsPbI₃, widely used to fabricate CsPbI₃, exhibits different phase transition behaviors than pure CsPbI₃. Here, we experimentally investigated the phase behavior of DMA-facilitated CsPbI₃ when exposed to external factors, such as heat and moisture. In DMA-facilitated CsPbI₃ films, the phase transition involving degradation was observed to begin at a temperature of 150 ℃ and a relative humidity of 65 %, which is presumed to be related to the sublimation of DMA. Forming a closed system to inhibit the sublimation of DMA significantly improved the phase transition under the same conditions. These results indicate that management of DMA is a crucial factor in maintaining the photo-active phase and implies that when employing DMA designs are necessary to ensure phase stability in DMA-facilitated CsPbI₃ devices.