Tailoring Pure-Phase Quasi-2D Perovskites via the Polymer Crystallization-Assisted Strategy

Pure-phase quasi-2D perovskites (PPQPs) with a flattened energy landscape feature higher color purities, less energy losses, and better optoelectronics performance as compared with multiple quantum well (QW) quasi-2D perovskites. However, to date, controllable fabrication of different n-value PPQP thin films remains an extremely formidable challenge. Here, by utilizing the polymer crystallization-assisted strategy, we successfully synthesized a series of PPQP films. Aligned −CF2– groups of precrystallized β-phase PVDF possess strong interactions with Pb2+, accurately assisting the PPQP nucleation and growth. With no polydisperse QWs, the final products only consist of single species QWs (from n = 1 to n ≥ 6). High-purity single-peak emissions from these PPQP films could be precisely targeted in a wide color gamut, covering the entire visible spectral region with high photoluminescence quantum yield (PLQY: 31.23% for blue, 58.74% for green, 70.94% for red, and 77.84% for near-infrared) and small full width at half-maximum. Hydrophobic PVDF surface passivation and encapsulation also improved the moisture stability and deformable properties. We fabricated the multicolor PPQP microring patterns as miniature pixel arrays, which can be potentially applied for backlight sources for light-emitting devices. Our finding provides a new guideline for designing pure-phase 2D perovskites, advancing their application in high-performance optoelectronic devices.