CsSnBr₃, A Lead-Free Halide Perovskite for Long-Term Solar Cell Application: Insights on SnF₂ Addition

Abstract

Solar cells based on “halide perovskites” (HaPs) have demonstrated unprecedented high power conversion efficiencies in recent years. However, the well-known toxicity of lead (Pb), which is used in the most studied cells, may affect its widespread use. We explored an all-inorganic lead-free perovskite option, cesium tin bromide (CsSnBr3), for optoelectronic applications. CsSnBr3-based solar cells exhibited photoconversion efficiencies (PCEs) of 2.1%, with a short-circuit current (J SC) of ∼9 mA cm–2, an open circuit potential (V OC) of 0.41 V, and a fill factor (FF) of 58% under 1 sun (100 mW cm–2) illumination, which, even though meager compared to the Pb analogue-based cells, are among the best reported until now. As reported earlier, addition of tin fluoride (SnF2) was found to be beneficial for obtaining good device performance, possibly due to reduction of the background carrier density by neutralizing traps, possibly via filling of cation vacancies. The roles of SnF2 on the properties of the CsSnBr3 were investigated using ultraviolet photoemission spectroscopy (UPS) and X-ray photoelectron spectroscopy (XPS) analysis.

Organic–Inorganic Copper (II)‐Based Perovskites: A Benign Approach toward Low‐Toxicity and Water‐Stable Light Absorbers for Photovoltaic Applications

“…The last two years have witnessed a tremendous surge in reports based on replacing the Pb in PSCs with nontoxic/less toxic transition metals. Gupta et al employed CsSnBr 3 as a light absorber, which showed a PCE of 0.6%. Liu et al prepared a mixed‐cation‐based (CH 3 NH 3 ) 0.9 Cs 0.1 SnI 3 light absorber and developed a PSC device, but the efficiency was found to be very poor (0.3%).…”

Fully‐Inorganic Trihalide Perovskite Nanocrystals: A New Research Frontier of Optoelectronic Materials

“…[141] Specially, with regard to Sn 2+ -containing perovskite NCs (e.g., CsSnX 3 ) and related devices, progress was strongly hampered by the transforming from Sn 2+ to Sn 4+ because Sn 2+ can easily be oxidized into Sn 4+ under ambient conditions. An in-situ protective strategy including introduction of reducing reagent such as tri-n-octylphosphine and hypophosphorous acid, [72,142] as well as additives like SnF 2 and SnBr 2 , [143][144][145][146] can improve the oxygen resistance and increase the stability under operating conditions. [64,110,142] In this case, the conventional coating technique to great extent cannot work efficiently.…”

Universal Dynamics of Molecular Reorientation in Hybrid Lead Iodide Perovskites

“…22,[51][52][53][54][55][56][57][58][59] Indeed, there are now numerous indications that the appealing optoelectronic properties of the hybrid perovskites are qualitatively matched by their all-inorganic analogues. 54,[60][61][62][63][64] In order then to delineate the properties and functionality of the molecular cations from those of the inorganic framework, one must first complete the description of the structure and dynamics of each. To this end, we employ solid-state NMR, a technique which is proved crucial for the study of plastic crystals.…”