Single crystal hybrid perovskite field-effect transistors

Abstract

The fields of photovoltaics, photodetection and light emission have seen tremendous activity in recent years with the advent of hybrid organic-inorganic perovskites. Yet, there have been far fewer reports of perovskite-based field-effect transistors. The lateral and interfacial transport requirements of transistors make them particularly vulnerable to surface contamination and defects rife in polycrystalline films and bulk single crystals. Here, we demonstrate a spatially-confined inverse temperature crystallization strategy which synthesizes micrometre-thin single crystals of methylammonium lead halide perovskites MAPbX₃ (X = Cl, Br, I) with sub-nanometer surface roughness and very low surface contamination. These benefit the integration of MAPbX₃ crystals into ambipolar transistors and yield record, room-temperature field-effect mobility up to 4.7 and 1.5 cm² V^-1 s^-1 in p and n channel devices respectively, with 10⁴ to 10⁵ on-off ratio and low turn-on voltages. This work paves the way for integrating hybrid perovskite crystals into printed, flexible and transparent electronics.

Fig. 1

Hybrid perovskite TSC fabrication. a Schematic representation of spatially confined inverse temperature crystallization method for producing thin single crystals (TSCs). b Fluorescence microscopy images of MAPbI₃, MAPbBr₃, and MAPbCl₃ TSCs (which are excited with a pulsed 450, 473, and 405 nm laser, respectively). Scale bar: 100 μm. Inset: optical images of MAPbI₃, MAPbBr₃, and MAPbCl₃ TSCs. Scale bar: 200 μm. c Height profile of MAPbBr₃ TSC indicating its thickness is about 2.45 µm. d XRD spectra of synthesized MAPbX₃ TSCs, where X = I, Br, and Cl, respectively

Fig. 2

Microstructure and surface properties of TSCs. a XRD data comparing the polycrystalline thin film (PTF) to the TSC and bulk single crystal (BSC) forms of MAPbBr₃. Surface topography of a MAPbBr₃ PTF (b) and that of a TSC (c) as measured by AFM, of which the root mean squared (RMS) roughness for PTF and TSC are 16.5 and 0.21 nm, respectively. Scale bar: 400 nm. d RMS surface roughness of MAPbX₃ (X = Cl, Br, and I) polycrystalline film and TSCs. The error bar reflects the statistical variation in roughness in different parts of the sample. e Scanning tunneling microscopy (STM) image of the surface region near the edge of a MAPbBr₃ TSC. Scale bar: 50 nm. f XPS spectra of the surface of MAPbI₃ TSC and BSC

Fig. 3

Characteristics of top-contact TSC-FETs. a Schematic of the bottom-gate, top-contact (BGTC) device with a TSC hybrid perovskite as semiconductor layer. Transfer characteristics (I_DS vs. V_GS (black solid square) and I_DS^1/2 vs. V_GS (red solid line)), as well as the fit lines (blue solid line) for b MAPbCl₃, c MAPbBr₃, and d MAPbI₃ TSC-FETs, V_GS ranging from −40 to 40 V. V_DS = −30 V. e Saturation mobility statistics for 60 devices. The box plot graphically depicts the statistical population of numerical data, including the maximum, the minimum, as well as the average (median) mobilities. Channel length: 50 μm. Output characteristics of TSC-FETs based on f MAPbCl₃, g MAPbBr₃, and h MAPbI₃

Fig. 4

Characteristics of bottom-contact TSC-FETs. a Schematic representation of bottom-gate, bottom-contact (BGBC) TSC-FET device. Representative transfer characteristics of TSC-FETs of b MAPbCl₃, c MAPbBr₃, and d MAPbI₃ using forward/reverse gate voltage sweeps from −10 to 10 V at a rate of 0.05 V s⁻¹, with V_DS = −2 V. Insets of b–d show the linear regime of the respective devices. e Field-effect hole mobility distribution for 20 devices fabricated and tested for each halide perovskite