Differential Response of the Photoluminescence and Photocurrent of Polycrystalline CH3NH3PbI3 and CH3NH3PbBr3 to the Exposure to Oxygen and Nitrogen
Konstantins Mantulnikovs a, Anastasiia Glushkova a, Márton Kollár a, László Forró a, Endre Horváth a, Andrzej Sienkiewicz a b
a Laboratory of Physics of Complex Matter, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
b ADSresonances SARL, Route de Genève 60B, CH-1028, Préverenges, Switzerland
Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics
Proceedings of International Conference on Perovskite and Organic Photovoltaics and Optoelectronics (IPEROP19)
Kyōto-shi, Japan, 2019 January 27th - 29th
Organizers: Hideo Ohkita, Atsushi Wakamiya and Mohammad Nazeeruddin
Poster, Konstantins Mantulnikovs, 045
Publication date: 23rd October 2018

The impact of gaseous media on photo-electronic properties of organic-inorganic metal halide perovskites (MHPs), such as methylammonium lead triiodide perovskite, CH3NH3PbI3 (MAPbI3), and methylammonium lead tribromide perovskite, CH3NH3PbBr3 (MAPbBr3), is not well understood. Here, the MHPs–based gas-sensing elements were grown by single-step solution coating on cylinder-shaped quartz substrates having diameters in the range from 80 μm to 1100 μm [1].  Particularly densely packed deposits, consisting of microwires and microcubes for MAPbI3 and MAPbBr3, respectively, were obtained for the smallest substrate diameters (80 μm and 330 mm). The elongated cylinder-shaped geometry and high surface-to-volume ratios of the thus prepared deposits revealed advantageous for designing miniature, light-transparent gas-flow chambers and made it possible to investigate the PL and PC responses of both MHPs exposed to the precisely controlled recurrent flow of either O2 or N2.  Moreover, small cross-sectional dimensions of the cylindrical substrates, having diameters of 80 μm or 330 μm, enabled us to position the deposits of two different MHPs side-by-side close to each other, thus making it possible to expose them simultaneously to the recurrently switched flows of either O2 or N2.

We found that under exposure to O2, the PL responses of MAPbI3 and MAPbBr3 were markedly opposite, i.e. the PL decreased for MAPbI3, whereas it increased for MAPbBr3. In contrast, under the exposure to N2, the PL of MAPbI3 increased, while it decreased for MAPbBr3. In addition, the simultaneous exposure of two different MHPs (positioned side-by-side) to the exactly identical environmental conditions clearly confirmed the differential responses of MAPbI3 and MAPbBr3 deposits to the recurrent flow of either of N2 or O2. A considerably differential behavior was also found for the PC responses. In particular, under exposure to O2, the PC strongly decreased for MAPbI3, whereas it markedly increased for O2.

In conclusion, the distinctly different PL and PC responses of polycrystalline deposits of MAPbI3 and MAPbBr3 to O2 and N2 reported herein point to markedly contrasting properties of the surface defects and carrier traps in these two MHPs. Moreover, by addressing dissimilar variations of the PL and PC of MAPbI3 and MAPbBr3 exposed to either O2 or N2, this study provides also a basis for the design of MHPs-based devices that are expected to function under various environmental conditions, including sensitive differential gas detectors.

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