Two-Step Crystallization for Low-Oxidation Tin-Based Perovskite Light-Emitting Diodes

Abstract

Metal halide perovskites attract significant attention because of their excellent optoelectronic and semiconducting properties. However, there are environmental concerns related to the toxicity of the lead metal that is mainly used in these perovskites. PEA2SnI4 perovskite is a potential candidate for lead-free perovskites because of its pure red emission. Although, undesired Sn4+ oxidation results in the deterioration of PEA2SnI4 perovskite. We demonstrate the two-step crystallization of PEA2SnI4 through the (i) reprecipitation and (ii) recrystallization processes. A film prepared using this method exhibits narrowed emission, with a full width at half-maximum from 30.0 to 26.1 nm, because of its homogeneous emission. Moreover, the Sn4+ content of two-step-crystallized PEA2SnI4 films is five times lower than that of a control film. Diffusion-ordered spectroscopy analysis indicates that the two-step precursor exhibits a smaller hydrodynamic radius crystal seed, which enhances crystallization during spin coating. The resulting two-step crystallized PEA2SnI4-based light-emitting diode (LED) exhibits a maximum external quantum efficiency (EQE) of 0.4% with an average of 0.2%, which is two times greater than that of the control device. This two-step approach may be generalized to synthesize other lead-free materials.

Color‐Stable Two‐Dimensional Tin‐Based Perovskite Light‐Emitting Diodes: Passivation Effects of Diphenylphosphine Oxide Derivatives

“…efficiencies (EQEs) over 20%, [7][8][9][10][11][12][13][14][15][16][17] the device performance of Sn-based PeLEDs is still in an earlier stage with maximum EQEs <6%. [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33] The performance gap between Sn-based and Pb-based perovskites has been ascribed to the trap-limited nonradiative recombination due to their inherent high-density defect states. [34] These traps are usually induced by the prone oxidation of Sn 2+ to Sn 4+ , and faster crystallization process of Sn-based perovskites than Pb analogs.…”

Composition and structure regulation of Ruddlesden–Popper perovskite for light-emitting diodes applications

“…57 PEA is also utilized as an organic spacer to form 2D perovskites for efficient PeLEDs. 29,52,[58][59][60][61][62][63][64][65][66] Kang et al added organic spacers with similar polarities. Still, different molecular lengths in the primary perovskite CsPbBr 3 yielded different distances between the crystalline structures, leading to the corresponding PL and EL emission color changes from green to blue.…”

Halide Chemistry in Tin Perovskite Optoelectronics: Bottlenecks and Opportunities

“…Since our initial work, research efforts within the scientific community have focused on improving the performance of red 2D Sn HaP LEDs. To this end, a number of strategies have been explored including: i) crystal growth engineering to yield more uniform thin films,[ 51 , 52 , 53 ] ii) dielectric confinement enhancement through organic cation replacement[ 54 , 55 ] and iii) the use of antioxidant additives. [ 56 , 57 ] To date, (PEA) 2 SnI 4 remains the champion 2D Sn HaP emitter, with record external quantum efficiencies (EQE) in LEDs of 5 % (Figure 4b ) [57] and showing promising upscaling prospects.…”