Supplemental Information. A Generic Route of Hydrophobic Doping. in Hole Transporting Material to Increase. Longevity of Perovskite Solar Cells

Transcription

1 JOUL, Volume 2 Supplemental Information A Generic Route of Hydrophobic Doping in Hole Transporting Material to Increase Longevity of Perovskite Solar Cells Laura Caliò, Manuel Salado, Samrana Kazim, and Shahzada Ahmad

2 Figure S1. Related to Figure 1B; Time evolution of the oxidation peak of doped Spiro- OMeTAD under illumination. UV absorption spectra of Spiro-OMeTAD with A) 5.3 mol%,b) 7.8 mol%, C) 10.1 mol%; D) 12.3 mol% BMPyTFSI and E) 50 mol% LiTFSI+330 mol% t-bp. For each different solution absorption spectra were recorded after 0 min (black line), 15 (red line), 20 (green line) and 30 min (blue line) of light exposure at 1 sun. The inset shows the zoom spectra of the oxidized Spiro-OMeTAD band at around 525 nm. As can be seen from Fig. S1 similar spectral features, like shown in Fig.1B, were observed for other molar concentration of BMPyTFSI and for conventional bi-component dopant LiTFSI and t-bp doped Spiro-OMeTAD at different illumination time. For conventional dopant, LiTFSI and t-bp, the employed concentration of LiTFSI was relatively high 330 mol% compare to ionic liquid dopant ( mol %) but the obtained results were comparable with a negligible difference in absorption intensity. In case of undoped, Spiro-OMeTAD, only absorption peak at 308 and 389 nm can be observed, and no new absorption band appears in the visible region after exposing to the light. Similar spectral features were also observed with Cobalt (III) complex doping where Cobalt complex chemically oxidizes Spiro-OMeTAD as shown in figure S2.

3 Figure S2. Comparison of the oxidation peak arises as a result of chemically doped and photo induced doped Spiro-OMeTAD. UV-vis absorption of Spiro-OMeTAD solution in chlorobenzene using conventional LiTFSI (50 mol%) + t-bp (330 mol%) + FK209 (10 mol%) dopant and LiTFSI (50 mol%) + t-bp (330 mol%) under 1 sun illumination (100mW/cm 2 ) showing appearance of the new peak at around 520 nm due to oxidation of Spiro-OMeTAD. Figure S3. Related to Figure 1F; Trend of absorption intensity at 520 nm as a function of BMPyTFSI concentration as shown in Fig.1F

4 Figure S4. 1 H NMR characterization. NMR spectra recorded in deuterated DMSO-d 6 for pristine, LiTFSI doped and BMPyTFSI doped Spiro-OMeTAD. Spiro-OMeTAD+BMPyTFSI: 1 H-NMR (DMSO): 8.97 (s, BMPy) (d, BMPy), (d, BMPy), (m, BMPy) (d, Ph, Spiro), (m, Ph+fluorene, Spiro), (m, Ph, Spiro), 6.17 (s, Ph, Spiro) (t, BMPy), 3.70 (s, OMe, Spiro), 2.49 (s, BMPy) (m, BMPy), (m, BMPy) (t, BMPy) Spiro-OMeTAD+LiTFSI+t-BP: 1 H-NMR (DMSO): 8.45 (s, Ph, t-bp) (d, Ph, Spiro), (d, Ph, t-bp) (m, Ph+fluorene, Spiro), (m, Ph, Spiro), 3.70 (s, OMe, Spiro), 1.3 (s, t-bu, t-bp) Spiro-OMeTAD pristine: 1 H-NMR (DMSO): (d, Ph), (m, Ph+fluorene), (m, Ph), 6.17 (s, Ph) 3.70 (s, OMe), In all these spectra Solvent: 2.5 (q, DMSO), impurity 3.3 (s, H 2 O)

5 Figure S5. Related to Figure 3A; Dark current measurement of mixed perovskite based solar cells using different dopants. J V curves in dark of best performing devices prepared with Spiro-OMeTAD as HTM using 7.8 mol% BMPyTFSI dopant, conventional dopant and additive LiTFSI, FK209, and t-bp. Undoped, Spiro-OMeTAD was also used as reference.

6 Figure S6. Photovoltaic characterization of MAPbI 3 based perovskite solar cell. A) J V curves of device prepared with conventional doped Spiro-OMeTAD and 7.8 mol% BMPyTFSI doped Spiro-OMeTAD as dopant, B) normalized PCE at maximum power point tracking for conventional and 7.8 mol% BMPyTFSI doped Spiro-OMeTAD with MAPbI 3 as light harvester.

7 Figure S7. Absorption measurements of perovskite films. UV-Vis absorption spectra of mixed perovskite-based devices with varying concentration of BMPyTFSI ionic liquid. The devices were prepared without Au metal contact (cathode) under the same conditions as of full device. Table S1. Summary of statistical photovoltaic parameters of PSCs calculated on 5 devices for each configuration. HTM composition V OC (V) J SC (ma cm -2 ) FF (%) PCE (%) Spiro mol% BMPyTFSI 1.00 ± ± ± ± 0.64 Spiro mol% BMPyTFSI 1.02 ± ± ± ± 0.24 Spiro mol% BMPyTFSI 1.00 ± ± ± ± 0.54 Spiro mol% BMPyTFSI 1.00 ± ± ± ± 0.65 Spiro + undoped 0.94 ± ± ± ± 0.57 Spiro + LiTFSI + t-bp + FK209 a 0.95 ± ± ± ± 0.64 Spiro + LiTFSI + t-bp 1.03 ± ± ± ± 0.37 a The molar concentration of LiTFSI, FK209 and t-bp used here was 50 mol%,10 mol% and 330 mol% respectively relative to Spiro-OMeTAD and (FAPbI 3 ) 0.85 (MAPbBr 3 ) 0.15 as light harvester.

8 Figure S8. Calculated Hysteresis index at maximum power point. J-V curves recorded in forward (red dotted lines) and reverse (black solid lines) bias for the devices with different HTLs, and the calculated hystresis index (HI) for each configuration.

9 Figure S9. Hysteresis index versus concentration analysis. Plot of hysteresis index(hi) with respect to the different concentration of BMPyTFSI as dopant for Spiro-OMeTAD and compared with other conventional dopants, HI was calculated from the best cell of each configuration. J-V curves are reported in Figure S8.

10 Figure S10. Top view of SEM images. Spiro-OMeTAD surface doped with different concentration of BMPyTFSI and conventional dopant.

11 Figure S11. Optical microscope images. Spiro-OMeTAD surfaces doped with different concentration of BMPyTFSI. It can be observed that the number of pinhole decreases with the increase in the concentration of BMPyTFSI.

12 Figure S12. Related to Figure 3C & 3D; Impedance spectroscopy (IS) measurements for MAPbI 3 perovskite based solar cells using different dopants. Nyquist plots, capacitance, and theta value were derived from the IS measurements at different bias voltage for solar cells based on MAPbI 3 perovskite and spiro-ometad doped with 7.8 mol% BMPyTFSI, LiTFSI+tBP and LiTFSI+tBP+FK209 dopant.

13 Figure S13. Photographic image of the mixed perovskite based devices kept outside in natural sunlight, (>50%RH) and monitored for a month. Images of the top-view (the above two row) and back-view (the down two row) of the devices with the different HTLs, stored in a controlled humidity chamber (50 %RH) for checking the visual effect of degradation after 1, 2, 4, 8 and 16 weeks. The labels next to the devices correspond to a different configuration of HTL, differing in Spiro-OMeTAD doping, as such: a) LiTFSI+t-BP+FK209; b) no doping; c) 5.3 mol%, d)7.8 mol% e)10.1 mol% and f) 12.3 mol% BMPyTFSI.