The Influence of Solvent Coordination on Hybrid. Organic-Inorganic Perovskite Formation. (Supporting Information)

Transcription

1 The Influence of Solvent Coordination on Hybrid Organic-Inorganic Perovskite Formation (Supporting Information) J. Clay Hamill, Jr., Jeffrey Schwartz, and Yueh-Lin Loo, * Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ Department of Chemistry, Princeton University, Princeton, NJ Andlinger Center for Energy and the Environment, Princeton University, Princeton, NJ *To whom correspondence should be addressed. Yueh-Lin Loo, Andlinger Center for Energy and the Environment, Princeton University, Princeton, NJ lloo@princeton.edu 1

2 Section 1: Materials and methods Materials. All reagents were used without further purification. PbI 2 with % purity, DMPU, DMSO, DMAC, NMP, DMF, GBL, EC, PC, TMS, ACN and NME were all purchased from Sigma-Aldrich. PEAI and BAI were purchased from DyeSol. The synthesis for MAI is reported elsewhere ; methylamine (CH 1 3NH 3, 33% in absolute ethanol), hydroiodic acid (57% in water), ethanol, and diethyl ether required for the synthesis of and purification of MAI were purchased from Sigma-Aldrich. Solubility studies. MAI and PbI 2 were dissolved at a 1:1 molar ratio at a total concentration of 1 M in the solvents of interest. The solutions were left to mechanically stir for 1 day in an N2 atmosphere and examined visually for signs of precipitation of precursors. Solvents that did not show precipitation after 1 day were allowed to stir for an additional 6 days and were judged to be stable if no precipitation was observed within this timeframe. E-SEM and SEM imaging. We prepared aliquots of the MAPbI3 precipitate with residual solvent and transferred these to sample stubs for environmental imaging using a FEI Quanta 200 FEG E-SEM. In the case of large crystals grown in solution and subsequently isolated and dried, images were obtained after mounting the crystals to carbon tape and a sample stub. A FEI Verios 460 XHR SEM was used to obtain the images. UV-vis absorption measurements. Aliquots of samples were prepared in an N2 atmosphere with a fixed amount of PbI2 and varying amounts of MAI. After 5 days, the samples were transferred to a vent hood for UV-vis absorption measurements using a Cary 5000 UV-vis spectrophotometer. The absorption spectrum of each aliquot was collected in the range of nm using a 1 cm quartz cuvette and the data was subsequently used for Benesi-Hildebrand analyses. 2

3 Thin-film fabrication. The method of substrate preparation is presented elsewhere. Briefly, S1 PEDOT:PSS was coated on glass substrates as a hole-transport layer typical of HOIP-based PV devices. MAI and PbI 2 were dissolved in the solvent mixture and stirred for 3 h in an N 2-filled glovebox. Subsequently, 0.1 ml of the solution was spin-coated on the substrate at 4000 rpm for 30 s. The films were subjected to thermal annealing at 70 C for 10 minutes and subsequently transferred to an SEM stub for imaging. Powder XRD characterization. Following the growth of HOIP single crystals, the samples were grounded and transferred to double-sided carbon tape for XRD characterization. A Bruker D8 Discover diffractometer using Cu Kα radiation source (λ = 1.54 Å) was used to obtain diffraction traces of the powders. The step size was 0.04 for all measurements. Device fabrication. Substrates were prepared using pre-patterned ITO-glass as the cathode. The substrates where cleaned and coated with PEDOT:PSS as described elsewhere. Afterwards, 1 precursor solutions containing 1:1 molar ratio of MAI to PbI 2 at total concentrations of 2.5 M were spin-coated on the substrates at 4000 rpm for 30 s. At specified times, (i.e., the time at which toluene washing took place) 0.5 ml of toluene was applied to the spinning substrates to extract residual solvent and induce MAPbI3 crystallization. The active layers were then annealed at 70 C for 1 m then 100 C for 5 minutes. Following thermal annealing, 30 nm of C60 (Sigma-Aldrich) and 5.5 nm of bathocuproine (BCP, Sigma-Aldrich) were deposited by sequential thermal evaporation. Finally, a 100-nm thick Al top electrode was thermally evaporated to complete the device stacks. The current-voltage (I-V) curves of the devices were measured with a Keithley 2635 source-measurement unit. A 300 Watt xenon lamp with a AM 1.5G filter was used as a solar simulator. To calibrate the light intensity of the solar simulator (to 100 mw/cm ), the power of the 2 3

4 lamp was adjusted so the short-circuit current density (Jsc) of a Newport model reference cell matched its specified calibrated value. Section 2: Supporting figures Figure S1: Powder XRD trace of MAPbI3 crystals grown in propylene carbonate. All reflections are consistent with the expected reflections of the tetragonal phase of MAPbI3. 4

5 Figure S2: Powder XRD trace of PEA2PbI4 crystals grown in propylene carbonate. The reflections are consistent with the expected layer spacing of PEA2PbI4. 5

6 Figure S3: Powder XRD trace of FA 0.83MA 0.17PbI 3 crystals grown in propylene carbonate. The reflections are consistent with the reported pattern for the cubic phase of FA0.85MA0.15PbI3, with S2 reflections shifted to slightly higher 2θ, corresponding to a smaller unit cell dimension, presumably due to the higher MA:FA ratio in our crystals. 6

7 Figure S4: a) Absorbance data for 0.2 mm PbI2 in DMF with increasing [MAI]:[PbI2]. As [MAI]:[PbI2] increases, the characteristic absorbance of PbI3- at λ = 370 nm decreases while the absorbance of PbI42- at λ = 420 nm increases. The spectra are stacked along the y-axis for clarity. b) Peak absorbances of PbI3- (open circles) and PbI42- (filled circles) as a function of [MAI]:[PbI2] in 0.2 mm PbI2 in DMF. c) Benesi-Hildebrand analysis of the UV-vis data presented in Figures S4a and S4b. The equilibrium constant for the formation of PbI42- in DMF is 9.8 ± 0.3 M. -1 7

8 Figure S5: (a) SEM images of FA 0.83 MA 0.17 PbI 3 films cast from precursor solutions comprising DMF as the solvent and (b) with 10% DMPU as an additive. Section 3: References (S1) Khlyabich, P. P.; Loo, Y.-L. Crystalline Intermediates and Their Transformation Kinetics during the Formation of Methylammonium Lead Halide Perovskite Thin Films. Chem. Mater. 2016, 28, DOI: /acs.chemmater.6b (S2) Huang, Y.; Li, L.; Liu, Z.; Jiao, H.; He, Y.; Wang, X.; Zhu, R.; Wang, D.; Sun, J.; Chen, Q.; et al. The intrinsic properties of FA (1 x) MA x PbI 3 perovskite single crystals. J. Mater. Chem. A 2017, 5, DOI: /C7TA01441D. 8