New discovery: Perovskite stability can be achieved by thiocyanate substitution

In a new study, researchers at the

Tokyo Institute of Technology demonstrated that the state _{of α-FAPbI3 can be stabilized at room temperature by introducing thiocyanate ions (SCN ^– ) into its structure. This is a promising solar cell material with cubic perovskite structure. Their findings provide new insights into the stabilization of the α phase by grain boundaries and pseudo-halide engineering.}

The study was published in the Journal of the American Chemical Society.

If used efficiently, the light we receive from the sun every day can help us deal with the current global energy crisis and concerns about climate change. Materials with good photophysical properties, or the ability to absorb light, are used to design solar cells that convert sunlight into electricity. The light

we receive from the sun every day, if used effectively, can help us solve the current global energy crisis, as well as our concerns about climate change. Materials with good photophysical properties, or the ability to absorb light, are used to design solar cells that convert sunlight into electricity. One material that has made recent progress

in this regard is α-formamide lead iodide or α-FAPbI3 _{(where FA + = CH (NH2 ) ² +), which is a crystalline solid with a cubic perovskite structure. The solar cell made}

of α-FAPbI3 demonstrated a superior conversion efficiency of 25.8% and an energy gap of 1.48 eV, specifications that are ideal for practical applications. Unfortunately, α-FAPbI _{3 FAPbI3 is metastable at room temperature, A phase transition to δ-FAPbI3 occurs when triggered by water or light . The energy gap of δ-FAPbI3 is much larger than ideal value for solar cell applications, making it crucial to keep α relative to practical applications.}

To solve this problem, a research team led by Professor Yamamoto of Tokyo Institute of Technology (Tokyo University of Technology) recently proposed a _{new strategy to stabilize α-FAPbI3. The team focused on the mechanism of stabilizing α-FAPbI3 by introducing the pseudo-halide thiocyanate ion (SCN ^– ). "Previous studies have shown that,"}

Dr. Yamamoto explained, Partial replacement of the surface anion _{of FAPbI3 from iodide (I –) to thiocyanate ion (SCN ^– ) can stabilize the α phase. However, how SCN ^– ions integrate in the perovskite lattice and increase the interfacial stability is still unclear. For the first time, the}

team prepared single crystal and powder samples of thiocyanate-stabilized pseudo-cubic perovskite. Structural analysis shows that it has a √ 5-fold superstructure of a cubic perovskite with ordered columnar defects, constituting the α 'phase. The new material is thermodynamically stable in a dry atmosphere at room temperature and exhibits an energy band gap of 1.91 eV.

The team found that the presence of the α 'phase in samples containing the δ phase can promote the phase transition from the δ to the α phase, lowering the transition temperature by more than 100 K. They pointed out that the defect ordering pattern in the α ′ phase can form a coincidence lattice at the bicrystal interface, stabilizing the α phase by lowering the nucleation energy or by epitaxial thermodynamic stabilization. These insights gained by the

researchers could facilitate further studies on the vacancy ordering and defect tolerance versus stability of halide perovskites. "This work shows that α-FAPbI3 can be stabilized by pseudo-halide ions and grain boundary engineering _{, which may be beneficial for scientists trying to develop new thermodynamically stable solar cell materials with ideal energy gap and excellent conversion efficiency," Dr. Yamamoto concluded.}