A research group led by Prof. HAN Keli from Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS) studied the dynamic mechanism of two-dimensional (2D) lead-free perovskites and developed new two-dimensional lead-free perovskites. Their findings were published in The Journal of Physical Chemistry Letters.
In recent years, 2D organic-inorganic perovskites have become a research hotspot in the field of photovoltaics, owing to their enhanced moisture stability and unique optical properties. Layered 2D perovskites have been known for decades, and they have been employed in light-emitting diodes (LEDs), solar cells, and photodetectors.
Despite the outstanding performance of lead-based 2D perovskites, environmental toxicity caused by lead still remains the main obstacle hampering their commercial utilization.
Tauc plots of (PEA)2Ge1-xSnxI4 (x=0, 0.125, 0.25, 0.5) and the photos of the compounds with different Sn content. (Image by CHENG Pengfei)
The researchers previously reported a lead-free, two-dimensional perovskite, (PEA)2GeI4 (J. Phys. Chem. Lett.).Based on previous work, they took (PEA)2GeI4 as the main body, in which an appropriate amount of tin was incorporated to form a series of two-dimensional germanium-tin mixed perovskites.
The bandgaps of these alloyed compounds decrease linearly with increasing tin content, leading to a tuning range of the bandgap from 2.13 to 1.95 eV. Among the perovskites reported, the smallest bandgap exhibited room-temperature photoluminescence (PL) with a lifetime over 2 ns.
Density functional theory calculations confirm that Sn substitution induces a smaller bandgap and more dispersed band structure. In addition, incorporation of Sn in 2D Ge-based perovskite can enhance its conductivity, thus providing an alternative mean to further improve the performance of photovoltaic materials.
This work was supported by the key research project of National Natural Science Foundation. (Text by CHENG Pengfei)