Environmentally Compatible Lead-Free Perovskite Solar Cells and Their Potential as Light Harvesters in Energy Storage Systems

Abstract

Next-generation renewable energy sources and perovskite solar cells have revolutionised photovoltaics research and the photovoltaic industry. However, the presence of toxic lead in perovskite solar cells hampers their commercialisation. Lead-free tin-based perovskite solar cells are a potential alternative solution to this problem; however, numerous technological issues must be addressed before the efficiency and stability of tin-based perovskite solar cells can match those of lead-based perovskite solar cells. This report summarizes the development of lead-free tin-based perovskite solar cells from their conception to the most recent improvements. Further, the methods by which the issue of the oxidation of tin perovskites has been resolved, thereby enhancing the device performance and stability, are discussed in chronological order. In addition, the potential of lead-free tin-based perovskite solar cells in energy storage systems, that is, when they are integrated with batteries, is examined. Finally, we propose a research direction for tin-based perovskite solar cells in the context of battery applications.

Keywords: energy storage systems; lead-free perovskite solar cells; photo-charging batteries; thin-film solar cells; tin perovskite.

Figure 1

(A) Bar graph showing the highest certified PCEs of the different types of photovoltaics. (B) Reported PCEs of Pb-based, Bi-based, and Sn-based PSCs from the initial stage of development to date. (C) Shockley–Queisser limit graph showing the PSC type that has a relatively high ideal bandgap. (D) PCE chart showing the development of Sn-PSCs.

Figure 2

(A) Proposed mechanism of hydrazine vapour reaction with Sn-based perovskite materials (reduction process: 2SnI₆²⁻ + N₂H₄ → 2SnI₄²⁻ + N₂ + 4HI). J–V curves for MASnI₃ solar cells, CsSnI₃ solar cells, and CsSnBr₃ solar cells with and without hydrazine vapour concentrations. Reprinted with permission from ref. [27] Copyright 2017, The American Chemical Society. (B) Schematic of the device structure, band alignment diagram, and a cross-sectional scanning electron microscope image of a completed device (scale bar: 500 nm). Reprinted with permission from ref. [30]. Copyright 2017, the John Wiley and Sons.

Figure 3

(A) Schematic representations of perovskite crystals in the presence of BAI and EDAI₂ additives. Reprinted with permission from ref. [34] Copyright 2018, the Royal Society of Chemistry. (B) Illustration of the vapour modification method discussed in this review. Reprinted with permission from ref. [36]. Copyright 2018, the John Wiley and Sons.

Figure 4

(A) Stabilised efficiency of power conversion and photocurrent density of two different devices tested in different environments. The measurement was taken at the position of maximum power for 1 sun irradiation with an AM1.5G solar simulator for 3600 s. Device reliability test conducted in (B) ambient air with relative humidity = 20% and 60% without encapsulation and (C) in N₂-filled glove box. (D) Efficiency of 8.30%, certified by ISO-approved PV Efficiency Verification Laboratory in Taiwan. Reprinted with permission from ref. [38] Copyright 2018, the John Wiley and Sons.

Figure 5

Schematic illustration of the optimum 4AMP functionalisation of grain surfaces and grain boundaries in FASnI₃ perovskite polycrystalline thin film, together with the J–V curves of the devices showing negligible hysteresis. Reprinted with permission from ref. [42] Copyright 2020, the American Chemical Society.

Figure 6

Schematic illustration of energy levels with dashed lines representing the quasi-Fermi level of ICBA (E_Fn–I), phenyl-C61-butyric acid methyl ester (PCBM) (E_Fn–P), and PEDOT:PSS (E_Fp). Reprinted with permission from ref. [50]. Copyright 2020, the Nature Publishing Group.

Figure 7

(A) Schematic of a fabricated system of LIB photo-charging by PSCs. (B) V–t curves of a fresh LIB cell measured at 0.5 C in the voltage range of 1.0–2.6 V for 15 cycles. (C) Cycling performance of different types of LIB cells measured at 0.5 C in the voltage ranges of 1.0–3.0, 2.5–4.0 and 1.0–2.6 V for 30 cycles. Reprinted with permission from ref. [54] Copyright 2015, the Nature Publishing Group.