Researchers from Purdue University and Harvard Medical School have demonstrated, for the first time, air-stable room-temperature lasing from quasi-2D tin iodide perovskite (TIP) microcrystals as small as 4 μm, enabled by a hydrogen-bonded organic spacer that dramatically improves environmental stability.
The team engineered Ruddlesden-Popper-type quasi-2D TIPs with the general formula (5IPA3)2(MA)n−1SnnI3n+1 (MA = methylammonium, n = number of perovskite layers), incorporating the organic cation 2-(3,5-dicarboxyphenoxy)ethan-1-aminium (5IPA3) as the spacer. The 5IPA3 molecule carries two carboxyl groups that form a robust, highly directional hydrogen-bonding network with the perovskite slabs, simultaneously suppressing oxygen permeation and increasing the mechanical rigidity of the lattice under high optical pumping. This spacer engineering yields 2D and quasi-2D 5IPA-based TIPs with substantially improved ambient stability in the dark and under photoexcitation compared with conventional PEA-based 2D TIPs.
Using these materials, the researchers realized air-stable room-temperature lasing from quasi-2D TIP microcrystals with n = 3 and n = 4, operating in crystals down to 4 μm in size. Lasing was observed in both dielectric microlasers (n = 4) and hybrid plasmonic microlasers (n = 3 and n = 4), demonstrating versatile cavity integration in ambient air. Importantly, the 5IPA-based quasi-2D TIPs achieved lasing with a threshold of approximately 200 kW/cm², significantly lower than earlier tin perovskite lasers that required peak powers in the GW/cm² range and inert-gas or cryogenic operation.
Under picosecond pumping, the microlasers maintained stable operation for over 10⁸ pump pulses in ambient conditions, even without encapsulation, underscoring the enhanced photostability provided by the 5IPA3 hydrogen-bonded network. The authors note that adding encapsulation, such as organic polymer coatings or noble-metal layers, could further extend device lifetimes for practical integration. This work also reports the first plasmonic lasing in TIPs, with optical gain coefficients for 5IPA3-n3 and 5IPA3-n4 compositions estimated to exceed 1,000 cm⁻¹, which the authors attribute to longer exciton diffusion lengths and enhanced intralayer energy transport in higher-n structures that strengthen the Purcell effect near gold substrates.
The combination of phase-pure, morphology-controlled microplates, quasi-2D Ruddlesden–Popper architecture, and 5IPA3-based hydrogen-bonded spacer engineering delivers high optical gain, low lasing thresholds (~200 kW/cm²), and long operational lifetimes (>10⁸ pulses) in air without encapsulation. These results establish a clear materials design route for lead-free tin iodide perovskite microlasers and provide a solid platform for future spacer and cavity optimization toward practical photonic and optoelectronic applications.
