| Autor: |
Freestone, B.G., Smith, J.A., Piana, G., Kilbride, R., Parnell, A., Sortino, L., Coles, D.M., Ball, O.B., Martsinovich, N., Thompson, C., Alanazi, T.I., Game, O.S., Tartakovskii, A., Lagoudakis, P.G., Lidzey, D.G. |
| Jazyk: |
angličtina |
| Rok vydání: |
2019 |
| ISSN: |
2050-7488 |
| Popis: |
Mixed-halide perovskites prepared from methylammonium iodide and lead chloride (MAPbI3−xClx) precursors are becoming increasingly well understood, however the effect of non-stoichiometry in this system is still not clear. Here, we create MAPbI3−xClx perovskites from starting mixtures containing an excess of MAI, and study them using a variety of structural and optical probes. Using grazing incidence X-ray scattering (GIWAXS) we demonstrate the existence of non-perovskite structures, and show that addition of hydroiodic acid (HI) also leads to similar low-dimensional phase formation. Photoluminescence spectroscopy performed at cryogenic temperatures indicates the existence of multiple emissive states between 510 nm and 605 nm resulting from a low dimensional phase (LDP) or multiple phases. By mapping the distribution of luminescence across the surface with submicron resolution, we found strong co-localisation of LDP emissive states. At certain blend ratios, emission is seen from both LDP states and methylammonium lead iodide perovskite (around 770 nm). Photoluminescence excitation spectroscopy of mixed-phase films reveals energy transfer, or a cascade, between different LDP states, but this process only occurs inefficiently to the surrounding perovskite. Time-resolved photoluminescence measurements demonstrate that LDP excited-state lifetimes decrease as a function of increasing temperature; a process consistent with a thermally-activated charge transfer process. Our work suggests that non-stoichiometric materials prepared via this processing route can lead to the formation of metastable LDPs with unique material properties that merit further investigation. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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