High-Performance Photocoupler Based on Perovskite Light Emitting Diode and Photodetector

Transcription

1 Supporting information for High-Performance Photocoupler Based on Perovskite Light Emitting Diode and Photodetector Zhi-Xiang Zhang, Ji-Song Yao, Lin Liang, Xiao-Wei Tong, Yi Lin, Feng-Xia Liang, *, Hong-Bin Yao, Lin-Bao Luo *, School of Electronic Science and Applied Physics, and Anhui Provincial Key Laboratory of Advanced Materials and Devices, Hefei University of Technology, Hefei, Anhui , China School of Materials Science and Engineering, Hefei University of Technology, Hefei, Anhui , China Hefei National Research Center for Physical Sciences at the Microscale, Department of Chemistry, CAS Center for Excellence in Nanoscience, Hefei Science Center of CAS, University of Science and Technology of China, Hefei, Anhui , China Corresponding Author * * S-1

2 EXPERIMENTAL SECTION Fabrication of perovskite QDs LED. The CsPbBr 3 QDs was synthesized by a hotinjection method. 5,41 Briefly, PbBr 2 (0.188 mmol) and 1-octadecene (ODE, 5.0 ml) were firstly added into a flask (30 ml) and stored under vacuum at 120 C for 2 hours. A mixed solvent containing oleinic acid (0.5 ml) and oleylamine (0.5 ml) were then injected into the above flask at 120 C under N 2 flow. In order to dissolve Cs 2 CO 3 powder which is used as the precursor for CsPbBr 3 QDs, Cs 2 CO 3 (0.814 g), OA (2.5 ml), and ODE (40 ml) were added into a large three-necked flask (100 ml) and dried for 1 h at 100 C. The as-formed oleate solution was then rapidly injected into the above PbBr 2 solution which was heated up to 185 o C. After 1 min reaction, perovskite QDs in green color was formed in three-necked flask. To fabricate the perovskite QD LEDs, PEDOT: PSS solutions which were filtered through a 0.22 μm filter were spin-coated onto ITO glass at 4000 rpm for 60 s, followed by baking at 140 C for 15 min. Chlorobenzene containing Poly-TPD (6 mg/ml) was then spin-coated on PEDOT:PSS layer at 1000 rpm for 60 s. After thermal annealing at 150 C for 20 min, the hotinjection derived CsPbBr 3 QDs were deposited by spin coating at 2000 rpm for 60 s. TPBi (40 nm) and LiF/Al electrodes (7 nm/100 nm) were deposited using a thermal evaporation system. Fabrication of perovskite photodetector. To assemble the photodetector, ITO glass (15 Ω/sq) was sequentially cleaned by detergent, acetone, and distilled water before use. Compact TiO 2 layer was then coated onto the ITO glass by spin-coating a n-butyl alcohol solution containing 0.15 M titanium diisopropoxide bis(acetylacetonate). S-2

3 Afterwards, FA 0.85 Cs 0.15 PbI 3 film in black-brownish color was coated by spin-coating a precursor containing 461 mg of PbI 2 (99.9%), 38.9 mg of CsI (99.9%), and 145 mg of FAI (Aldrich, 99.5%), followed by addition of 20 μl of diethylether (99%) solution. A Spiro-OMeTAD layer as HTL was then spin-coated on the films at 5000 rpm for 40 s. Finally, 180 nm Au film was thermally evaporated on the top of device as an electrode. Note that all the above experiments were carried out in glove box. Materials characterization and Photocoupler analysis. The morphology and crystal structure of perovskite film, LED, and photodetector were analyzed using a SEM (Hitachi, SU8020) and TEM instrument (JEOL model JEM-2100F). The absorption spectra and XRD pattern of FA 0.85 Cs 0.15 PbI 3 perovskite film were recorded on a Shimadzu UV-2500 UV-Vis spectrophotometer and an X-ray diffractormeter (Rigaku 501D/max-rB), respectively. The EL spectra, density luminance-voltage characteristics and the external quantum efficiency (EQE) of the perovskite QDs LED was characterized by a home-assembled setup composed of a fiber integration sphere, PMA- 12 spectrometer and a 2400-Keithley source. A 510 nm laser diode (Tanon Company, UV-100) was used to illuminate the photodetector for optoelectronic property study. To fabricate the photocoupler, epoxide resin was used to bond the perovskite LED and photodetector on ITO glass. A low-power negative-positive-negative silicon transistor (S8050) was included in the circuit to increase the CTR value. During device analysis, a 2400-Keithley was used to drive the perovskite LED, and the photodetector was studied by a semiconductor characterization system (4200-SCS, Keithley Co. Ltd.). To measure the response speed of the photocoupler, a signal generator (Tektronix, S-3

4 TDS2022B) was used to drive the LED to produce a high-frequency incident light and an oscilloscope (Tektronix, TDS2012B) was employed to record the electrical data. Figure S1. (a) TEM images of CsPbBr 3 QDs which are used for fabrication perovskite LED. (b) The statistical distribution of the diameter of CsPbBr 3 QDs. S-4

5 Figure S2. The SEM image of FA 0.85 Cs 0.15 PbI 3 perovskite film at both low magnification (a), and high magnification (b). (c) Schematic illustration of the crystal structure of the FA 0.85 Cs 0.15 PbI 3 material. (d) The X-ray diffraction (XRD) patterns of FA 0.85 Cs 0.15 PbI 3 film. Figure S3. (a) PL spectrum of the CsPbBr 3 quantum dots and the inset was the digital photograph. (b) EQE of the CsPbBr 3 QDs LED. S-5

6 Figure S4. (a) Wavelength-dependent specific detectivity. (b) EQE of the photodetector. Calculation the responsivity (R), specific detectivity (D*) and external quantum efficiency (EQE) of the photodetector: we calculated responsivity (R), external quantum efficiency (EQE), and specific detectivity (D*), both of which are crucial performance figure-of-merits of a photodetector. R is defined as the photocurrent generated per unit power of the incident light on the effective area of a photodetector, while EQE is the ratio between the number of electron-hole pairs with contribution to the photocurrent and the number of incident photons at a given wavelength, the detectivity that is usually used to describe the smallest detectable signal, can be described by the following equation which are usually expressed by the following equation: R = I ph P λ S = EQE ( eλ hc)g R A D* (2 ei ) d 1/2 1/2 (1) (2) where P λ, S, e, λ, h, c, G, A, I d are the incident light intensity, effective illuminated area (0.1 cm 2 ), elementary charge, light wavelength, Planck s constant, speed of light and S-6

7 photoconductive gain, device effective area (0.1 cm 2 ), the dark current ( ), respectively. The G is unity in common photodiodes without internal gain mechanism. Therefore, according to the equation, R, EQE and D* were estimated to be 0.7 AW -1, 160% and Jones, respectively. S-7