Efficient Ideal‐Bandgap Tin–Lead Alloyed Inorganic Perovskite Solar Cells Enabled by Structural Dimension Engineering

Abstract

as solution processability and cost-effectiveness, thus being considered as one of the most promising photovoltaic technologies. [1] Currently, the state-of-the-art PSCs usually contain large amounts of an organic monovalent cation such as methylammonium (MA + ) and formamidinium (FA + ) which are volatile and hygroscopic under elevated temperatures and humid conditions. [2] The shortcomings of these organic cations have rendered the PSCs with low thermal stability and moistureinduced degradation, raising significant long-term stability concerns for the commercialization of PSCs. [3] The substitution of organic cations with inorganic cations such as cesium (Cs + ) or rubidium (Rb + ) to form inorganic perovskite has proved to effectively enhance the device's thermal and moisture-resistant ability as well as photostability. [4] Within a few years, the power conversion efficiencies (PCEs) of inorganic PSCs have boosted from 5.95% to impressive record efficiency of 21.0% which bridges the gap with their organic-inorganic counterparts. [5] Despite the remarkable improvement, the optical bandgaps of Pbbased inorganic perovskites vary from 1.73 eV for CsPbI 3 to 2.32 eV for CsPbBr 3 which are much wider than the optimal Inorganic tin-lead alloyed perovskite solar cells with optimal bandgap have gained increasing attention because of their higher theoretical efficiency limit, inherently robust stability, and potentials in all-inorganic perovskite tandems. However, their efficiency has far lagged from their Pb-based counterparts owing to some intractable problems such as poor crystallization and facile Sn 2+ oxidation. Here, a small amount of 2D perovskite PEAPb 0.7 Sn 0.3 I 4 is utilized to regulate the crystallization process of 3D CsPb 0.7 Sn 0.3 I 3 based on the temperature-gradient annealing method. The X-ray diffraction results show that a stable intermediate phase composed of 3D perovskite seeds and 2D phases is formed under a lower annealing temperature of 50 °C, and the pre-crystallized 3D perovskites can promote the subsequent crystallization upon 80 °C annealing to attain high quality film. It is interesting that the 2D perovskite phase is ultimately mainly located between the 3D perovskite phase and hole transport layer as revealed by the time of flight-secondary ion mass spectrometry. The resulting perovskite exhibits a lower extent of non-radiative recombination and better stability. Consequently, the device achieves a champion efficiency of 14.6% setting a new record for inorganic tin-lead perovskite solar cells (PSCs). This work sheds more light on the future progress of inorganic tin-lead PSC.

Enhancing Photovoltaic Performance through Optimized Antisolvent Strategy for Low-Bandgap Pb–Sn Perovskites

“…They are characterized by their exceptional optoelectronic properties, wide-ranging light absorption from the visible to near-infrared (NIR) regions, and a tunable bandgap. The lower bandgap of Pb–Sn perovskites enables the harnessing of photons with lower energy, making these materials suitable for all-perovskite tandem solar cells and NIR light-emitting diodes. − Despite these advantages, the current efficiency of Pb–Sn mixed PSCs lags behind that of their Pb-based counterparts, with reported efficiencies ranging from 10% to 23.6%. − The inclusion of Sn contributes to a rapid crystallization process, largely due to the strong Lewis acid character of SnI 2 . This behavior can result in the formation of defects and lattice distortions in the perovskite films.…”