Pressure-Assisted Space-Confined Solvent- Engineering Strategy for Ultrasensitive. Photodetectors

Transcription

1 High-Quality CH NH PbI Films Obtained via Pressure-Assisted Space-Confined Solvent- Engineering Strategy for Ultrasensitive Photodetectors Xianwei Fu, Ning Dong, Gang Lian,*,, Song Lv, Tianyu Zhao, Qilong Wang, Deliang Cui,*, and Ching-Ping Wong*, State Key Lab of Crystal Materials, Shandong University, Jinan 00, P.R. China Key Laboratory for Special Functional Aggregated Materials of Education Ministry, School of Chemistry & Chemical Engineering, Shandong University, Jinan 00, P.R. China School of Materials Science and Enigneering, Georgia Institute of Technology, Atlanta, Georgia 0, United States 1 *Corresponding author: 1 liangang@sdu.edu.cn; 1 cuidl@sdu.edu.cn; 1 cpwong@cuhk.edu.hk 1

2 Experiment Section Fabrication of MAPbI thin film by conventional annealing method The chemical reagents used for preparing MAPbI films were PbI (AR, Aladdin Industrial Corporation, Shanghai, China), methylammonium iodide (MAI, AR, Tokyo Chemical Industry Co., Ltd, Tokyo, Japan), dimethylsulfoxide (DMSO, AR, Sinopharm Chemical Reagent Co., Ltd, China), dimethylacetamide (DMAC, AR, Sinopharm Chemical Reagent Co., Ltd, China) and isopropanol (IPA, AR, Sinopharm Chemical Reagent Co., Ltd, China). All the reagents were used as received without further purification. The MAPbI film was prepared by the spin-coating method as illustrated in Figure 1. According to the previous reported result, 1 the existence of excessive MAI could facilitate the growth of MAPbI grains and improve their stability in ambient air, thus the molar ratio of PbI and MAI was set at 1:1. in our experiments. In a typical process, 0. g PbI and 0.1 g MAI were dissolved in a mixed solvent of dimethylsulfoxide (DMSO) and dimethylacetamide (DMAC) in volume ratio of 1:1 at ºC under stirring, and the solution was continuously stirred for 1 h for preparing the precursor solution. Prior to the preparation of MAPbI film, the glass substrate was thoroughly cleaned by following the cleaning process of silicon wafers. Afterwards, 0 µl of precursor solutions was spin-coated onto the glass substrate at 0 rpm for s, followed by another spin-coating process at 000 rpm for 0 s. The MAPbI films were preheated at 0 ºC for min, and further annealed at 0 ºC for 0 min. The resultant MAPbI film was denoted as conventional annealing (CA) film. All these manipulation processes were performed in a glove-box filled with high purity (.%) nitrogen gas.

3 Fabrication of MAPbI films by pressure-assisted space-confined and pressure-assisted space-confined solvent-engineering strategies The preheated precursor films were firstly placed in a glass desiccator fulfilled with saturation IPA vapor for 1 h in glove-box, thus the IPA vapor was uniformly adsorbed on the surface of precursor film (Figure 1). The ambient temperature was kept constant at ~0 C during this process. Afterwards, a silicon wafer was covered on top of the film. After being tightly wrapped with Teflon membrane, the packed film and silicon wafer were transferred into a hot-press autoclave (see Figure S) fulfilled with simethicone. During the experimental process, the simethicone serves as the uniform transmission medium for both the heat and pressure. Thirdly, a pressure of 00 MPa was applied on the autoclave, and the temperature was increased to 0 C at a rate of C/min. After kept at 0 C and 00 MPa for h, the autoclave was cooled to room temperature at a rate of 0.01 C/min. Finally, when the pressure was released, the obtained MAPbI film was denoted as PSS film. For comparing the effect of IPA vapor, a control samples were prepared by following the same experimental processes, except that no solvent vapor was introduced into the precursor film (Figure 1), thus the PS film was prepared. 1 Measurements and Characterization X-ray diffraction (XRD) analysis was conducted using a Bruker-AXS D Advance X-ray diffractometer with Cu K α radiation (λ=1.1 Å), and the scanning speed was 0.0 s/step. Fourier transformation infrared (FTIR) spectra of the samples were recorded on a Thermo- Nicolet NEXUS 0 infrared spectrometer. The morphology of the samples was observed using a Hitachi S-00 field-emission scanning electron microscope (SEM) and a scanning probe atomic force microscope (SPM, Veeco Instruments Inc, Dimension Icon). Lattice images and

4 1 1 fringes of the samples were recorded on a JEOL JEM-0 high resolution transmission electron microscope (HRTEM). Optical absorption spectra of the samples were recorded using a Hitachi UV-Vis NIR. An Edinburgh FLS0 luminescence spectrometer was used to characterize the photoluminescence (PL) performance of the samples, and a laser of nm was used as the excitation source. Time-resolved photoluminescence (PL) decay spectra were acquired using the time-correlated single-photon counting technique (FluoTime 00, PicoQuant GmbH). I-V and dynamic response curves of the MAPbI film photodetector were recorded on a Keithley 00- SCS semiconductor parameters analyzer at room temperature in N atmosphere. The time dependent photoresponse signal was recorded by digital oscilloscope with a Keithley 00-SCS semiconductor parameters analyzer in N atmosphere. Before the characterization, the sealed sample chamber was under vacuum using a pump. Then residual air in the chamber was completely expelled with high purity N to avoid the influence of H O and O. The entire measuring procedure was completed in N atmosphere

5 Figure S1 FTIR spectrum of the preheating MAPbI film. The absorption peak at ~ cm -1 corresponds to the PbI DMSO precursor

6 Figure S (a) XRD patterns of the CA, PS and PSS MAPbI films. (b) Peak intensity ratios of (1) to () planes for the CA, PS and PSS MAPbI films.

7 Figure S (a, c) AFM topography and three-dimensional topographic images of the PSS MAPbI film, respectively. (b, d) AFM topography and three-dimensional topographic images of the individual grain based on PSS films.

8 Figure S HRTEM image of the CA film. Inset is the corresponding SAED pattern.

9 Figure S (a) Grain-size distributions of the perovskite films prepared by pressure-assisted space-confined (PS) method. (b) Statistical size distribution of crystal grains in the pressure- assisted space-confined solvent-engineering (PSS) film.

10 Figure S Top-view SEM images of the PSS films. (a) With hexane solvent fumigation. (b)with cyclohexane solvent fumigation.

11 Figure S Schematic diagram of electrode size and hot-press autoclave. 1 1

12 Absorbance(a.u.) Wavelenghth (nm) Figure S The UV-vis spectra of the MAPbI CA film. 1 1

13 Figure S Transient response curves at different irradiance wavelengths with various power density of the photodetector based on PSS films. 1 1

14 Figure S Photo-response characteristics of the photodetector based on PSS films. (a) I V characteristics of MAPbI photodetector under light illumination at 1 nm with the different light power density. (b) Dependency of photocurrent on incident light power density and bias voltage at 1 nm laser. (c) Linear dynamic range of the MAPbI photodetector, i.e., photocurrent vs incident light intensity under 1 nm at V bias. 1

15 Figure S The dark current change at 1 nm laser under different dark time with various power density of the photodetector based on PSS films. A dark time of 00 s (a) and 0 s (b). Because the MA dipole alignment can be induced by light and bias applied across the MAPbI material, the structural change to the inorganic framework of the MAPbI easily affects the polarity and conductivity of perovskite. However, the adjustment of the inorganic scaffold is very slow and then a long time is needed for the current recovering to a steady-state value. When the light is turned off for a longer time, such as ~00 s, the current can decline to a steadystate value (Figure Sa). However, the dark current of the device can not recover to a stable state with dark time for 0 s after illumination and then the dark current slightly increases (Figure Sb)

16 Figure S1 Photo-response characteristics of the photodetector based on PS films. (a) Transient response curves at different irradiance wavelengths with various power density. (b) Stability measured under various illumination power density for 1 nm laser. (c) The I light /I dark ratio of the photodetectors under different illumination power densities for 1 nm laser. (d) The light intensity dependent detectivity of the PS film photodetectors at 1 nm laser. 1

17 Figure S1 Photo-response characteristics of the photodetector based on CA films. (a) Transient response curves at different irradiance wavelengths with various power density. (b) Stability measured under various illumination power density for 1 nm laser. (c) The light intensity dependent detectivity of the CA film photodetectors at 1 nm laser

18 Table S1 Performance comparison of our PSS film-based photodetector with other reported similar photodetectors (all lateral configuration). Materials Channel Incidence Detectivity Photocurrent On/off Rise/deca Ref (µm) light (Jones) y time MAPbI 0 0 nm. 1 na 0. ms/ nanowire ( V, 0 µw/cm ) 0. ms MAPbI 00 0 nm na ms/ nanowire ( V,0 µw/cm ) 0. ms MAPbI 00 nm. 1 µa. ms/ film ( V, mw/cm ) ms MAPbI 0 nm. 1 > µa _ 0 µs/ microwire (0 V, 1 mw/cm ) 0 µs MAPbI 00 0 nm. 1 na < ms/ microwire ( V, 0.1 mw/cm ) ms MAPbI 00 1 nm 1. 1 ~ µa ~. µs/ This film ( V, 0. mw/cm ) 0 µs work 1

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