Universal Synthesis of Large-Area Hybrid Perovskite Monolayers Enabling Lithography-Free, Low-Static-Power Optoelectronics
Solution-phase synthesis of monolayer hybrid organic-inorganic perovskites is constrained by rapid out-of-plane crystal growth, uncontrolled nucleation, and strong interlayer aggregation, yielding flakes of only a few μm. We introduce a steric-engineering ternary-solvent growth strategy to synthesize monolayer and few-layer A2MX4 hybrid perovskites with exceptionally large surface areas. By combining alcohol cosolvents with an amine additive, out-of-plane stacking is suppressed. Using (PEA)2CuCl4 as a model system, monolayers with lateral areas exceeding 1000 μm2 are achieved, representing a massive dimensional increase over conventional methods. Molecular dynamics and quantum-chemical calculations show that longer-chain alcohols reorganize precursor solvation, while solvent volatility prolongs edge-mediated precursor transport during annealing. This strategy demonstrates universal applicability across diverse organic spacer cations (PEA+, F-PEA+, PentA+), metal centers (Cu2+, Mn2+, Pb2+), and halides (Cl-, Br-, I-). The large lateral dimensions enable direct, solvent-free electrical contact fabrication via physical shadow masking, bypassing chemical degradation from solvents used in conventional lithography. Planar devices fabricated from isolated ultrathin (PEA)2PbI4 channels exhibit ultra-low dark currents down to the 10^-15 - 10^-13 A range, enabling femtowatt-to-picowatt static power consumption, ~ 0.2 pW at 5 V, a 250-fold reduction relative to drop-cast films, while maintaining a high light-to-dark current ratio of 4.3 x 102. This work establishes precise steric and solvation control as a paradigm for scalable, compositionally diverse, low-static-power monolayer 2D perovskite optoelectronics.