Improving the Bulk Emission Properties of CH3NH3PbBr3 by Modifying the Halide-Related Defect Structure
David O. Tiede a, Juan F. Galisteo-López a, Maurico E. Calvo a, Hernán Míguez a
a Instituto de Ciencia de Materiales de Sevilla (ICMS-CSIC), C/ Américo Vespucio 49, Seville, 41092, Spain
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, David O. Tiede, 138
Publication date: 11th February 2019

The outstanding potential of halide perovskite for optoelectronic devices has been widely demonstrated over the past years. In particular, the defect chemistry of hybrid organic–inorganic lead halide perovskites is believed to be partially responsible for the optical performance of this solution-processed material. In this work, the role of bromine-based defects on the emission properties of CH3NH3PbBr3 is investigated.

Herein, micron sized single crystals are analyzed to study effects on surface and bulk emission as they are exposed to bromine vapors. We follow the evolution of the emission by means of photoluminescence (PL) microscopy as well as spectral and time resolved measurements. This allows us to carry out a complete analysis with spatial, spectral and temporal resolution of the emission from these systems. Through this study we find evidence for a strong PL improvement through bromine vapor treatment which remains for tens of hours. We observe bromine penetration into the material which positively affects bulk emission.  A defect-related mechanism behind this improvement is proposed which takes into account crystal orientation and the nature of bromine defects as deep or shallow traps. Furthermore, an insight on spatial distribution of light emission origins in the material is given.  

With these results we help understand the defect structure in these materials and present a post-fabrication method to improve the emission throughout the entire volume of CH3NH3PbBr3 in the absence of appreciable degradation. 

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