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Clement Livache1 2 Wasim Mir4 Eva Izquierdo1 Bertille Martinez1 2 Mathieu Silly3 Benoit Dubertret1 Sandrine Ithurria1 Emmanuel Lhuillier2

1, ESPCI, Paris, , France
2, Université Pierre et Marie Curie, Paris, , France
4, ISER, Pune, , India
3, Synchrotron SOLEIL, Saint-Aubin, , France

Perovskites quantum dots (PQDs) have rapidly emerged as a new generation of light emitting nanocrystals despite their very recent report.1 However their transport2,3 and electronic properties4 remain poorly investigated which prevents the device optimization. In this paper we propose a procedure for the integration of PQD into conductive and photoconductive film.5 We demonstrate that the proposed film preparation can be applied to other halide PQDs compositions and shapes. We use X-ray photoemission to unveil the electronic spectrum of the PQDs, bring evidence of their n-type character and report a value of 4.1 eV for the work function of CsPb(Br0.65,I0.35)3 PQDs. Using a combination of high bandwidth transient photocurrent and DC photocurrent measurements, we show that the large exciton binding energy prevents efficient dissociation of the generated photocharges. We thus propose to use nanotrench electrodes as a path to boost the material photoresponse and report an enhancement by a factor 1000.

References

1. Protesescu, L.; Yakunin, S.; Bodnarchuk, M. I.; Krieg, F.; Caputo, R.; Hendon, C. H.; Yang, R. X.; Walsh, A.; Kovalenko, M. V. Nanocrystals of Cesium Lead Halide Perovskites (CsPbX3, X = Cl, Br, and I): Novel Optoelectronic Materials Showing Bright Emission with Wide Color Gamut. Nano Lett. 2015, 15, 3692-3696.
2. Kwak, D. H.; Lim, D. H.; Ra, H. S.; Ramasamy, P.; Lee, J. S., High Performance Hybrid Graphene-CsPbBr3-xIx Perovskite Nanocrystal Photodetector. RSC Adv. 2016, 6, 65252-65256.
3. Palazon, F.; Di Stasio, F.; Lauciello, S.; Krahne, R.; Prato, M.; Manna, L., Evolution of CsPbBr3 Nanocrystals upon Post-Synthesis Annealing under an Inert Atmosphere. J. Mater. Chem. C 2016, 4, 9179-9182.
4. Ravi, V. K.; Markad, G. B.; Nag, A. Band Edge Energies and Excitonic Transition Probabilities of Colloidal CsPbX3 (X = Cl, Br, I) Perovskite Nanocrystals. ACS Energy Lett. 2016, 1, 665-671.
5. Swarnkar, A.; Marshall, A. R.; Sanehira, E. M.; Chernomordik, B. D.; Moore, D. T.; Christians, J. A.; Chakrabarti, T.; Luther, J. M. Quantum Dot–Induced Phase Stabilization of α-CsPbI3 Perovskite for High-Efficiency Photovoltaics. Science 2016, 354, 92-95.

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