Key Takeaways & Executive Findings
- •• Cosolvent-coordinated crystallization at ≤40 °C enables planar integration of micrometer-thick Sn–Pb single-crystal films with high structural and composition integrity. • A tailored solvent matrix yields thickness-tunable single-crystal thin films with ultralow trap densities (~3.98 × 10^12 cm−3) and robust ambient stability. • Integrated near-infrared photodetectors achieve 73.8% EQE, 0.51 A W−1 responsivity, 3.6 × 10^12 Jones specific detectivity, and stable performance over 25,000 cycles. • This work establishes a scalable platform for redox-stable, low-temperature growth of Sn–Pb perovskite crystal films, expanding the processing–structure–function landscape for next-generation infrared optoelectronics.
Abstract
Tin–lead (Sn–Pb) halide perovskite single crystals combine narrow bandgaps, long carrier diffusion lengths, and low trap densities, positioning them as ideal candidates for near-infrared (NIR) optoelectronics. However, conventional growth strategies rely on bulk crystallization at elevated temperatures, leading to uncontrolled nucleation, Sn2+ oxidation, and poor compatibility with planar integration. Here, we develop a coordination-engineered crystallization strategy that enables direct, low-temperature growth of micrometer-thick Sn–Pb single-crystal thin films on device-compatible substrates. By modulating metal–solvent coordination strength using a low-donor number cosolvent system, we delineate a narrow processing window that stabilizes precursor speciation, lowers the nucleation barrier, and guides directional crystal growth under mild thermal conditions (< 40 °C). The resulting crystal films exhibit smooth morphology, high crystallinity, compositional uniformity, and ultralow trap densities (~ 3.98 × 10^12 cm−3). When integrated into NIR photodetectors, these films deliver high responsivity (0.51 A W−1 at 900 nm), specific detectivity up to 3.6 × 10^12 Jones, fast response (~ 188 μs), and > 25,000 cycles of ambient operational stability. This approach establishes a scalable platform for redox-stable, low-temperature growth of Sn–Pb perovskite crystal films and expands the processing–structure–function landscape for next-generation infrared optoelectronics.
1. Introduction
Near-infrared (NIR) optoelectronics are pivotal to advancing energy-efficient sensing, biomedical imaging, and optical communication [1, 2], yet remain constrained by the lack of scalable semiconductors that combine deep NIR absorption with ambient stability and low-temperature processability [3, 4]. Crystalline silicon and InGaAs offer excellent NIR responsivity but are constrained by high cost, mechanical rigidity, and limited compatibility with solution-based fabrication [5, 6]. Metal halide perovskites offer an attractive alternative, with tunable bandgaps, long carrier diffusion lengths, and intrinsic solution processability [7, 8]. Tin–lead (Sn–Pb) halide perovskites are among the few solution-processable semiconductors capable of accessing bandgaps near 1.2 eV, with high absorption coefficients and intrinsic carrier mobilities well suited for infrared detection [7, 8]. However, integrating Sn–Pb perovskites into practical planar devices remains fundamentally limited by their redox sensitivity and structural inhomogeneity [11]. Polycrystalline films suffer from grain-boundary recombination, phase segregation, and rapid Sn2+ oxidation, while surface passivation offers only incremental improvements to a defect-rich microstructure [14, 15].
Single-crystal thin films (SCTFs) offer a structurally coherent, trap-suppressed alternative, but scalable low-temperature growth compatible with planar device integration remains elusive [16, 17]. Recent efforts to grow Sn–Pb SCTFs have highlighted a narrow and poorly defined processing window. For instance, MAPb0.5Sn0.5I3 crystal films grown via inverse-temperature crystallization at ~95 °C exhibited high thickness and crystallinity, but required thermal conditions that accelerate Sn2+ oxidation and limit integration with temperature-sensitive substrates [18]. Attempts to reduce processing temperatures through Sn-deficient formulations have led to bandgap broadening (~1.35 eV), compromising NIR absorption [19]. Together, these studies highlight a core limitation in Sn–Pb crystallization: the lack of a chemically defined processing window that enables low-temperature, planar growth without compromising material quality.
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Rajendra Kumar Gunasekaran, Jihoon Nam, Myeong-geun Choi, Won Chang Choi, Sunwoo Kim, Doyun Im, Yeonghun Yun, Yun Hwa Hong, Sang Hyeok Ryou, Hyungwoo Lee, Kwang Heo, Sangwook Lee (2026). Monolithic Integration of Redox-Stable Sn–Pb Halide Perovskite Single-Crystalline Films for Durable Near-Infrared Photodetection. Nano-Micro Letters. https://doi.org/10.1007/s40820-025-01991-y
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Frequently Asked Questions
What is the main achievement of this paper?
The paper demonstrates a coordination-engineered crystallization strategy for growing micrometer-thick Sn–Pb halide perovskite single-crystal thin films at temperatures below 40 °C, enabling their monolithic integration into durable near-infrared photodetectors with high performance and stability.
How does the low-temperature crystallization work?
The method uses a low-donor number cosolvent system to modulate metal–solvent coordination strength, stabilizing precursor speciation, lowering the nucleation barrier, and guiding directional crystal growth under mild thermal conditions.
What are the key performance metrics of the photodetectors?
The integrated NIR photodetectors achieve 73.8% external quantum efficiency, 0.51 A W−1 responsivity at 900 nm, specific detectivity up to 3.6 × 10^12 Jones, fast response time of ~188 μs, and stable operation over 25,000 cycles.
Why are Sn–Pb perovskites important for NIR detection?
Sn–Pb halide perovskites have narrow bandgaps near 1.2 eV, high absorption coefficients, and long carrier diffusion lengths, making them ideal for efficient near-infrared photodetection.
What is the significance of this work for future applications?
This work provides a scalable, low-temperature platform for growing redox-stable Sn–Pb perovskite crystal films, which could enable next-generation infrared optoelectronics with improved performance and integration capabilities.
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