Morphological and Electronic Tailoring: Insights into Zero Dimensional Bismuth Based (CH3NH3)3Bi2I9 Lead Free Perovskites
Priya Shrivastava a, K.R. Balasubramaniam b, Parag Bhargava c
a Centre for Research in Nanotechnology and Science, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
b Department of Energy Science and Engineering, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
c Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV19)
Roma, Italy, 2019 May 12th - 15th
Organizers: Prashant Kamat, Filippo De Angelis and Aldo Di Carlo
Poster, Priya Shrivastava, 001
Publication date: 11th February 2019

Efforts towards replacement of the benign Bi for lead in perovskite light absorber have redoubled. However, synthetic challenges due to the non 3D perovskite structure in the Bi-based perovskites are difficult to overcome. Recent reports suggests alternate ways by using vapor based techniques however these methods are not very cost effective and scalable. Here, we tackle this problem by choosing solution processing methods and achieve a high coverage film. We demonstrate Br-doping of the zero dimensional (CH3NH3)3Bi2I9 perovskites to fine tune the electronic properties. A simple two step deposition technique, using a preferred precursor solvent and optimized concentration of methylammonium halide salts has been used for fabricating pure I and Br-doped perovskite analogues. X-ray Photoelectron Spectroscopy (XPS) results reveal that Br-doped films are less prone to degradation as compared to pristine films. Also, the amount of degradation of the Spiro-perovskite interface in a device employing un-doped perovskite is larger compared to that in a Br-doped perovskite based device.

The authors would like to acknowledge the support from the Center of Excellence in
Nanoelectronics (CEN) for device fabrication facility, Central Surface Analytical Facility (ESCA)
Department of Physics, IIT Bombay, and the National Center for Photovoltaic Research and
Education (NCPRE) for characterization facilities. P.S. thanks the University Grants Commission
for the UGC (NET-JRF) Fellowship for the financial support. We are thankful to Professor Arindam Chowdhury, IIT Bombay,
for providing PL facility.

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