Kinetic Studies of Oleylamine-Based 2D-Lead Bromide Perovskite with Controllable n-Value by Sequential Addition of Cesium at Room Temperature

The outstanding properties of lead-basedperovskite nanomaterialshave led researchers to investigate the potential of their two-dimensional(2D) perovskite counterparts with the chemical formula A(2)& PRIME;A( n+1)B( n )X(3n+1). Despite their advantages suchas better stability and higher exciton binding energy, the synthesisof phase pure 2D perovskite nanomaterials remains challenging dueto the fast nucleation process. Here, we demonstrate a simple andefficient method to synthesize 2D perovskite nanomaterials with phasepure specific n-values. The room-temperature nucleationand growth of perovskites with specific n-valuesare controlled in a two-step synthesis method by the optimized amountof cesium. Our 2D perovskite nanomaterials with specific n-values exhibit high-purity photoluminescence (PL) peaks in the rangefrom deep-blue to azure-blue emission color. X-ray diffraction andattenuated total reflectance-Fourier transform infrared spectroscopywere used to elucidate the kinetic reaction of oleylamine with PbBr2 and the effect of cesium addition in the formation of 2Dperovskite nanomaterials. In situ PL studies were also performed tocalculate the activation energy (E (a)) ofdifferent specific n-value nanomaterials by usingthe Arrhenius equation. This study not only helps visualize the effectof addition of Cs amount on the stacking of monolayers of [PbBr6](4-) octahedrons but also provides an easierway to control the n-value in 2D perovskite nanomaterials.