Localized Electron Density Engineering for Stabilized B-γ CsSnI₃-Based Perovskite Solar Cells with Efficiencies >10%

Abstract

Black orthorhombic (B-γ) CsSnI3 with low toxicity and excellent optoelectronic properties is a promising candidate for perovskite solar cell (PSC). However, the performance of the B-γ CsSnI3-based PSCs is much lower than their lead-based or organotin-based counterparts due to the heavy self-doping of Sn2+ to form Sn4+ under ambient-air conditions. Here, this undesirable oxidation in CsSnI3 is restricted by engineering the localized electron density with phthalimide (PTM) additive. The lone electron pairs of NH and two CO units of PTM are designed to form trigeminal coordination bonding with Sn2+, resulting in reduced defect density and relatively grain-ordered perovskite film. The champion efficiencies of 10.1% and 9.6% are obtained for the modified rigid and flexible B-γ CsSnI3-based PSCs, respectively. These encapsulated devices maintain 94.3%, 83.4%, and 81.3% of their initial efficiencies under inert (60 days), ambient (45 days), and 1 Sun continuous illumination at ∼70 °C (2000 min) conditions, respectively.

Over 8% efficient CsSnI3-based mesoporous perovskite solar cells enabled by two-step thermal annealing and surface cationic coordination dual treatment

“…14 Recently, Ye et al used localized electron density engineering to restrict undercoordinated Sn 2+ , resulting in reduced defect density and relatively grain-ordered CsSnI 3 films. 29 Herein, we combine the aforementioned two principal issues, proposing the two-step temperature annealing and surface cationic coordination dual treatment strategy (DTS) to achieve high-performance CsSnI 3 PSCs. The first annealing step at a low temperature of 40 °C for 5 min slows down the crystal growth of CsSnI 3 films and produces many small crystal grains.…”

Enhanced Stability of Tin Halide Perovskite Photovoltaics Using a Bathocuproine—Copper Top Electrode

“…[7] Promisingly, Li et al have shown that CsSnI 3 perovskite inverted PV devices maintained >90% of their starting efficiency after 500 h light soaking when encapsulated with glass. [30] To understand the intrinsic stability of perovskite PVs with a Cu top electrode toward degradation in ambient air, which inevitably ingresses into the device even with encapsulation, it is useful to test the devices in ambient air under 1 sun constant illumination and under electrical load. Without device encapsulation such a test is clearly an accelerated degradation test, since for practical application PV devices would always be encapsulated and so the rate of air ingress into the device would be many orders of magnitude slower.…”

Regulating the phase stability and bandgap of quasi-2D Dion–Jacobson CsSnI3 perovskite via intercalating organic cations

“…With record PCEs beyond 10.1%, 16–18 CsSnI 3 perovskite solar cells (PSCs) have shown an increasing competitive edge. 19–22 CsSnI 3 can hold two crystal phases at room temperature, namely, the corner-linked three-dimensional (3D) black orthorhombic phase (B-γ) perovskite and the edge-connected one-dimensional (1D) yellow phase (Y) one.…”

“…19–22 CsSnI 3 can hold two crystal phases at room temperature, namely, the corner-linked three-dimensional (3D) black orthorhombic phase (B-γ) perovskite and the edge-connected one-dimensional (1D) yellow phase (Y) one. 17 However, once exposed to air or organic solvents, B-γ-CsSnI 3 rapidly degrades to Y-CsSnI 3 , subsequently leading to severely attenuated PCEs under ambient conditions. 17,23 Compared to Y-CsSnI 3 , the superior photoelectric properties of B-γ-CsSnI 3 depends on the 3D corner-shared [SnI 6 ] 4− octahedral structure, which benefits the transport of photo-induced carriers along …Sn–I–Sn–I–Sn… chains.…”

“…17 However, once exposed to air or organic solvents, B-γ-CsSnI 3 rapidly degrades to Y-CsSnI 3 , subsequently leading to severely attenuated PCEs under ambient conditions. 17,23 Compared to Y-CsSnI 3 , the superior photoelectric properties of B-γ-CsSnI 3 depends on the 3D corner-shared [SnI 6 ] 4− octahedral structure, which benefits the transport of photo-induced carriers along …Sn–I–Sn–I–Sn… chains. Nevertheless, B-γ-CsSnI 3 is a low-symmetry perovskite phase caused by lattice distortion, which will inevitably affect the carrier mobility, thus limiting the PCE.…”