Controlled on-chip fabrication of large-scale perovskite single crystal arrays for high-performance laser and photodetector integration

Metal halide perovskites have shown great promise in photovoltaics due to their excellent optoelectronic properties and solution-based fabrication. Perovskite solar cell efficiency has significantly increased over the past decade. This success has spurred the development of perovskite-based optoelectronic devices, including photodetectors, light-emitting diodes, lasers, and field-effect transistors, demonstrating enhanced performance and potential for revolutionizing the optoelectronic industry. Most of these devices utilize continuous polycrystalline films, a common approach in photovoltaics. However, many optoelectronic applications require discrete perovskite layers for functional integration. To enhance device performance, the development of perovskite single-crystal arrays with improved chemical stability, lower defect density, and higher carrier mobility is crucial. Traditional photolithography and etching techniques are often incompatible with perovskites due to their poor chemical stability in polar solvents. Previous attempts to fabricate perovskite single-crystal arrays have involved two-step vapor-phase methods or one-step processes using templates and capillary forces or inkjet printing. These methods, however, are typically limited to blank substrates and lack the precise control needed for on-chip fabrication and alignment with pre-existing patterns. This research addresses this gap by developing a method for on-chip fabrication with precise control over individual pixel properties, enabling both the fabrication of devices based on individual crystals and their direct integration into large-scale optoelectronic devices.

The literature extensively documents the remarkable progress in perovskite solar cell technology, highlighting the material's superior optoelectronic properties and its potential for high-efficiency energy conversion. Numerous studies explore the application of perovskites in diverse optoelectronic devices, showcasing their versatility. However, the challenges in fabricating large-scale, precisely controlled perovskite single-crystal arrays for integrated applications remain a significant hurdle. The existing methods, such as vapor-phase deposition and inkjet printing, suffer from limitations in terms of control over crystal size, shape, and alignment. The lack of a reliable method for on-chip fabrication with precise control over individual pixel properties has hindered the development of integrated perovskite-based optoelectronic systems. This study aims to bridge this gap by presenting a novel fabrication technique that enables the precise control and integration needed for high-performance applications.

This research introduces a one-step space confinement and antisolvent-assisted crystallization (SC-ASC) method for fabricating high-quality single-crystalline MAPbBrxCl3−x (MA = CH3NH3, x = 0, 1, 2, 3) microplate (MP) arrays on various substrates. The method involves three key elements: (1) substrate engineering to ensure accurate pixel positioning; (2) space confinement to regulate contact line extraction and prevent residue; and (3) antisolvent crystallization to improve crystal quality. The process begins with a pre-patterned substrate with hydrophilic areas created through surface functionalization. The precursor solution is confined to these hydrophilic areas by a hydrophobic glass cover, maintaining a 20 µm gap between the substrates. An antisolvent is then introduced, leading to controlled crystallization. The method's effectiveness in producing large-scale single-crystalline perovskite MPs arrays is demonstrated by fabricating a 10 × 10 cm array with 1250 × 1250 pixels. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD) are used to characterize the morphology and crystal structure of the arrays. The influence of antisolvent and space confinement on crystal growth is also investigated. The control over pixel dimensions (2–8 µm width), positioning (less than 10% variation), and in-plane rotation is demonstrated, along with the versatility of the method, allowing fabrication on various substrates including metal electrodes, ITO, and PET. The use of epitaxial substrates such as SrTiO3 (STO) and KTaO3 (KTO) is explored to control in-plane crystal rotation. The optical properties of the arrays, including lasing behavior, are characterized using confocal microscopy, a femtosecond laser source, and a spectrometer. Color tunability is achieved by varying the halogen composition of the perovskite.

The SC-ASC method successfully fabricated large-scale (100 cm²) homogeneous perovskite single crystal arrays with high precision. Pixel position accuracy was maintained within 10% variation, and pixel dimensions were tunable from 2 to 8 µm. The in-plane rotation of individual pixels was also controllable. The resulting perovskite microplates acted as high-quality whispering gallery mode (WGM) microcavities with a quality factor (Q) of 2915 and a low lasing threshold of 4.14 µJ cm². On-chip fabrication directly onto patterned electrodes produced a vertical structured photodetector array with stable photoswitching and pattern imaging capabilities. The method demonstrated versatility across various substrates (glass, ITO, NiO, PET) and allowed for the creation of different array patterns. Using epitaxial substrates (STO, KTO), the in-plane crystal rotation was precisely controlled. The perovskite single crystals exhibited a low trap density (1.05 × 10¹² cm⁻³) and high carrier mobility (111.4 cm² V⁻¹ s⁻¹). Multicolor perovskite arrays were created by adjusting the halogen composition (MAPbBr3−xClx, x = 0, 1, 2, 3), resulting in tunable emission wavelengths from 542 nm (green) to 410 nm (blue).

The findings demonstrate a significant advancement in the controlled fabrication of perovskite single crystal arrays. The ability to precisely control pixel position, dimensions, and in-plane rotation opens new possibilities for creating integrated optoelectronic devices. The high quality of the resulting perovskite microplates, evidenced by their excellent lasing characteristics and low trap density, is crucial for high-performance applications. The successful fabrication of a functional photodetector array highlights the potential of this method for integrating perovskites into complex systems. The versatility of the SC-ASC method, enabling fabrication on various substrates and achieving multicolor emission, greatly expands its applicability. This work addresses a significant challenge in the field, providing a pathway towards large-scale integration of perovskite-based optoelectronics.

This research successfully demonstrates a novel SC-ASC method for controlled on-chip fabrication of large-scale perovskite single crystal arrays. This method offers precise control over crystal array properties, including pixel position, size, and in-plane rotation, leading to high-quality WGM microcavities and functional photodetector arrays. The versatility and precision of this method pave the way for the development of advanced integrated optoelectronic devices and systems. Future research could explore the integration of these arrays into more complex devices and the optimization of the method for even larger-scale fabrication and diverse perovskite compositions.

While this study demonstrates significant progress, some limitations exist. The current method's scalability for even larger areas needs further investigation. The long-term stability of the fabricated perovskite arrays under various environmental conditions remains to be fully assessed. The exploration of other perovskite compositions and their integration into diverse device architectures would broaden the scope of this technology. Further optimization of the antisolvent and space confinement parameters may improve the uniformity and yield of the process.