Electronic Supplementary Material (ESI) for Journal of Materials Chemistry A. This journal is The Royal Society of Chemistry 2015 Supporting Information 1. Synthesis of perovskite materials CH 3 NH 3 I was synthesized by reacting methylamine (37.2 ml, 33 wt% in ethanol, Aladdin) and hydroiodic acid (40 ml, 57% in water, Aldrich) in an ice bath for 2 h under stirring. Hydroiodic acid was added dropwise during stirring. The resulting solution was evaporated at 50 C to produce a white powder. The crude product was then dissolved in ethanol to form a saturated solution and recrystallized by diethyl ether. The resulting product was further washed for three times with diethyl ether and dried under vacuum. To form the non-stoichiometric CH 3 NH 3 PbI 3-x Cl x precursor solution (40 wt%), CH 3 NH 3 I (0.801 g) and PbCl 2 (0.468 g, 99% Aldrich) were first mixed in anhydrous dimethylformamide (DMF, Aldrich). 1 wt% of 1,8-diiodooctane (DIO, Alfa Aesar) was added to the CH 3 NH 3 PbI 3-x Cl x precursor solution and then stirred overnight at 80 C. The resulting solution was filtered by poly (vinylidene fluoride) filters with a diameter of 0.45 µm. 2. Preparation of the spinnable CNT array CNT arrays were grown by chemical vapor deposition with Fe (1.2 nm)/al 2 O 3 (3 nm) on a silicon substrate as the catalyst at 740 C. Ethylene was used as the carbon source, and a gas mixture of Ar and H 2 was used as the carrier gas. The flow rates of Ar, H 2, and C 2 H 4 were typically 400, 30, and 90 sccm, respectively. CNT arrays with thicknesses of about 250 m were mainly used in this work. 3. Electrodeposition of perovskite layer. Electrodeposition process was operated in an aqueous solution of 2 mm Pb(NO 3 ) 2 and 0.2 M H 2 O 2 with modified Ti wire acted as a working electrode and Pt wire served as a counter electrode. Then, the as-prepared Ti wire was immersed in hydriodic acid for 0.5 h, followed by immersing in the CH 3 NH 3 I solution (10 mg in 1ml DMF) for 5 minutes. Finally, it was annealed at 100 C for 2h. 4. Characterization The structures were characterized by SEM (Hitachi FE-SEM S-4800 operated at 1 kv). X-ray diffraction patterns were obtained from an X-ray powder diffractometer (D8 ADVANCE and DAVINCI.DESIGN). The absorbance spectra were recorded from an UV-Vis Spectrophotometer (Shimadzu, UV-2550). J-V curves were produced S1
by a Keithley 2400 Source Meter under illumination (100 mw/cm 2 ) of simulated AM1.5 solar light coming from a solar simulator (Oriel-Sol3A 94023A equipped with a 450 W Xe lamp and an AM1.5 filter). The light intensity was calibrated using a reference Si solar cell (Oriel-91150). S2
Figure S1. Schematic illustration to the calculation of the effective area of the working electrode. S3
Figure S2. Scanning electron microscopy (SEM) image of CH 3 NH 3 PbI 3-X Cl X layer coated on aligned TiO 2 nanotubes (a) and nanoparticles (b) without assistance of DIO. S4
Figure S3. X-ray diffraction pattern of CH 3 NH 3 PbI 3-X Cl X layer annealed for 0.5 h without DIO. S5
Figure S4. Typical J-V curves of elastic PSCs with and without DIO. S6
Figure S5. (a) UV-vis absorption spectra of dilute CH 3 NH 3 PbI 3-X Cl X precursor solution with different concentrations of DIO. (b) Labelled red rectangle at (a). S7
Figure S6. (a) SEM image of a spinnable CNT array. (b) Optical image of a transparent conducting CNT sheet. S8
Figure S7. High-resolution transmission electron microscopy (TEM) image of a CNT. S9
Figure S8. X-ray diffraction pattern of TiO 2 with an anatase structure. S10
Figure S9. Bottom view of an aligned TiO 2 nanotube array. S11
Figure S10. Cross-sectional SEM images of aligned TiO 2 nanotubes grown with the increasing time. (a) 10 min. (b) 20 min. (c) 30 min. (d) 40 min. S12
Figure S11. SEM images of a broken compact TiO 2 layer that was dip-coated for 5 times at low (a) and high (b) magnifications. S13
Figure S12. Different thickness of TiO 2 nanoparticles layers. (a) ~0.9 μm. (b) ~2.2 μm. (c) ~3.6 μm. (d) ~5.8 μm. S14
Figure S13. Cross-sectional SEM image of a Ti wire coated with compact TiO 2, TiO 2 nanoparticles, CH 3 NH 3 PbI 3-X Cl X and hole transport layer. S15
Figure S14. (a) A spring-shaped TiO2 nanotube-modified Ti wire coated with CH3NH3PbI3-XClX. (b-d) Higher magnifications of (a) at different regions. S16
Figure S15. UV-vis spectra of an aligned MWCNT sheet. S17
Figure S16. J-V curves of a series of elastic fiber-shpaed PSCs with the same TiO 2 nanotube (length of 1.6 μm) modified electrode. S18
Table S1. Photovoltaic parameters in Figure S16. Sample V OC /mv J SC /ma cm -2 FF η/% number 1 629 3.46 0.47 1.01 2 633 3.26 0.48 0.99 3 630 3.44 0.48 1.04 4 634 3.31 0.49 1.03 5 622 3.22 0.51 1.02 6 612 3.16 0.52 1.01 7 620 3.53 0.48 1.05 8 633 3.46 0.51 1.12 9 625 3,34 0.52 1.08 10 628 3.61 0.48 1.09 S19
Figure S17. Schematic illustration to an elastic PSC fiber based on TiO 2 nanoparticles on the Ti wire electrode. S20
Figure S18. J-V curve of an elastic PSC without the outermost aligned CNT sheet. S21
Figure S19. J-V curve of an optimized fiber-shaped PSC. S22
Figure S20. SEM image of the perovsktie layer on the spring-shaped electrode after stretching for 100 cycles with a strain of 30%. S23
References for the Supporting Information [S1] M. R. Lee, R. D. Eckert, K. Forberich, G. Dennler, C. J. Brabec, R. A. Gaudiana, Science 2009, 324, 232-235. [S2] W. Guo, C. Xu, X. Wang, S. Wang, C. Pan, C. Lin, Z. L. Wang, J. Am. Chem. Soc. 2012, 134, 4437-4441. [S3] Y. Fu, Z. Lv, S. Hou, H. Wu, D. Wang, C. Zhang, Z. Chu, X. Cai, X. Fan, Z. L. Wang, Energy Environ. Sci. 2011, 4, 3379-3383. [S4] Z. Yang, H. Sun, T. Chen, L. Qiu, Y. Luo, H. Peng, Angew. Chem. Int. Ed. 2013, 52, 7545-7548. [S5] B. Weintraub, Y. Wei, Z. L. Wang, Angew. Chem. Int. Ed. 2009, 121, 9143- - 9147. S24