Highly Oriented Low-Dimensional Tin Halide Perovskites with Enhanced Stability and Photovoltaic Performance

Abstract

The low toxicity and a near-ideal choice of bandgap make tin perovskite an attractive alternative to lead perovskite in low cost solar cells. However, the development of Sn perovskite solar cells has been impeded by their extremely poor stability when exposed to oxygen. We report low-dimensional Sn perovskites that exhibit markedly enhanced air stability in comparison with their 3D counterparts. The reduced degradation under air exposure is attributed to the improved thermodynamic stability after dimensional reduction, the encapsulating organic ligands, and the compact perovskite film preventing oxygen ingress. We then explore these highly oriented low-dimensional Sn perovskite films in solar cells. The perpendicular growth of the perovskite domains between electrodes allows efficient charge carrier transport, leading to power conversion efficiencies of 5.94% without the requirement of further device structure engineering. We tracked the performance of unencapsulated devices over 100 h and found no appreciable decay in efficiency. These findings raise the prospects of pure Sn perovskites for solar cells application.

Highly Reproducible Sn‐Based Hybrid Perovskite Solar Cells with 9% Efficiency

“…[23][24][25] Unlike the comprehensive studies on lead-based perovskite, only two papers about tin-based HPSCs using lowdimensional perovskite such as (CH 3 (CH 2 ) 3 NH 3 ) 2 (CH 3 NH 3 ) n-1 Sn n I 3n+1 and PEA 2 FA n−1 Sn n I 3n+1 (n is the number of the inorganic SnI 6 octahedra layers encapsulated by the PEA + (PEA = C 6 H 5 (CH 2 ) 2 NH 3 + ) double layer, the increase (decrease) in n value means increase (decrease) in the dimension; n = ∞ 3D perovskite, n = 1 2D perovskite) were published during the preparation of this manuscript. [26,27] In both papers, the PCE of the tin-based HPSCs are still lower than 6%. Cao et al reported a PCE of 2.5% by using (CH 3 (CH 2 ) 3 NH 3 ) 2 (CH 3 NH 3 ) 3 Sn 4 I 13 (n = 4) as light harvesting layer.…”

“…[26] Ning and co-workers reported a PCE of 5.9% using PEA 2 FA 8 Sn 9 I 28 (n = 9) as light harvesting layer. [27] For the low-dimensional tin-based perovskite family (CH 3 (CH 2 ) 3 NH 3 ) 2 (CH 3 NH 3 ) n-1 Sn n I 3n+1 and PEA 2 FA n−1 Sn n I 3n+1 , how the device using tin perovskite with lower content of bulkier organic cations (∞ >n > 5 for CH 3 (CH 2 ) 3 NH 3 ) 2 (CH 3 N H 3 ) n−1 Sn n I 3n+1 , ∞ > n > 9 for PEA 2 FA n−1 Sn n I 3n+1 ) as light harvesting layer behaves, remains an open question.…”

Lead‐Free Hybrid Perovskite Absorbers for Viable Application: Can We Eat the Cake and Have It too?

“…The 2D tin perovskite outperformed its 3D analogs for higher moisture stability with an encouraging PCE of 2.5% (from n = 4). More importantly, incorporating 20% phenyl ethyl ammonium (PEA) into FA‐based Sn iodide perovskites yielded low dimensional (PEA) 2 (FA) 8 Sn 9 I 28 64 which exhibited markedly enhanced air stability in comparison with their 3D counterparts FASnI 3 . The inverted structure‐based devices with (PEA) 2 (FA) 8 Sn 9 I 28 perovskite exhibited the best PCE up to 5.94% and showed super stability over 100 h without encapsulation.…”

“…The role of DMSO was to retard the crystallization of FAI and SnI 2 during spin‐coating process ( Figure 11 a–d). The realized smooth and dense perovskite layer enables a maximum efficiency up to 4.8% for FASnI 3 ‐based PSCs and the encapsulated devices kept stable for over 100 d. The same method was also applied in low‐dimensional tin halide perovskites (PEA) 2 (FA) 8 Sn 9 I 28 to obtain compact and smooth perovskite surface morphology 64. Chlorobenzene,161 as a common antisolvent applied in lead‐based PSCs, was adopted by Zhang et al60 as antisolvent to achieve a dense FASnI 2 Br film giving a device PCE of 1.72%.…”

“…Additionally, the poor morphology of the tin halide perovskite layer has been improved by the various fabrication methods. Recently, great progress has been made in Sn‐based PSCs with inverted device architecture,28, 56, 64, 66, 67 due to the omission of doped HTMs. Unlike Pb‐based PSCs where the high efficiencies are usually achieved with doped HTMs, the use of dopants will accelerate the deterioration of tin perovskites.…”