1 Supporting Information Size Tunable Cesium Antimony Chloride Perovskite Nanowires and Nanorods Bapi Pradhan † , Gundam Sandeep Kumar † , Sumanta Sain ‡ , Amit Dalui †,§ , Uttam Kumar Ghorai ¶ , Swapan Kumar Pradhan # and Somobrata Acharya* ,† † Centre for Advanced Materials, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032, India ‡ Department of Materials Science, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032, India § Department of Chemistry, Jogamaya Devi College, Kolkata 700026, India ¶ Department of Industrial & Applied Chemistry, Swami Vivekananda Research Center, Ramakrishna Mission Vidyamandira, Belur Math, Howrah 711202, India # Department of Physics, The University of Burdwan, Burdwan 713104, West Bengal, India *Corresponding author email: camsa2@iacs.res.in Table of Contents 1. Low resolution TEM images and EDX of CSC NWs……………………..…………………….....................................................................Figure S1 2. UV-vis, PL spectra and photographs of CSC NWs......................................................................................................................Figure S2 3. Raman spectra of CSC NWs..........................................................................................................................................................Figure S3 4. XPS of CSC NWs……….………………………...……….....……………………..................................................................................................Figure S4 5. FTIR spectra of CSC NWs and NRs…...........................................................................................................................................Figure S5 6. TGA of CSC NWs..........................................................................................................................................................................Figure S6 7. Cs−Cl bond lengths in the axial hexagon within the triangular orthobicupola.......................................................................Figure S7 8. XRD and TEM image of pure trigonal phase……………………………………………………………………………………….................................Figure S8 9. XRD and TEM image of pure orthorhombic phase……….……..……………………............................................................................Figure S9 10. Structural parameters from Rietveld analysis of mixed phase CSC NWs..................................................................................Table S1 11. XRD of CSC NWs under ambient condition…………………….……………........................................................................................Figure S10 12. TEM image of uncontrolled morphologies……………………………………........................................................................................Figure S11 13. Absorbance of CSC NRs with annealing time variation ……..…….……......................................................................................Figure S12 14. XRD of CSC NRs …………..………………...……….......……..................................................................................................................Figure S13 15. Raman spectra of CSC NWs.......................................................................................................................................................Figure S14 16. Experimental setup for photoconductivity measurements.....................................................................................................Figure S15 17. Photoswitching performance of CSC NRs................................................................................................................................Figure S16 18. Photodetector performances comparison…………………………………………......................................................................................Table S2