Quasi cw lasing and runaway heating in trihalide perovskites

Feipeng Chen^a, Michele Cadelano^a, Giovanni Bongiovanni^a, Valerio Sarritzu^a, Nicola Sestu^a, Daniela Marongiu^a, Francesco Quochi^a, Andrea Mura^a, Michele Saba^a

^aUniversità di Cagliari - Dipartimento di Fisica, Cittadella Universitaria, Monserrato, 0, Italy

International Conference on Hybrid and Organic Photovoltaics
Proceedings of International Conference on Hybrid and Organic Photovoltaics 2015 (HOPV15)

Roma, Italy, 2015 May 11th - 13th

Organizer: Filippo De Angelis

Oral, Michele Saba, presentation 135
Publication date: 5th February 2015

What makes trihalide lead perovskites a great materials system for photovoltaic applications suggest their successful employ also as active media in LEDs and lasers. Particularly, high emission efficiency under intense excitation, high carrier mobility and films with good optical quality are all desirable properties for a lasing medium. Few recent studies have demonstrated stimulated emission in perovskite films under ultrafast pulsed laser excitation. Such regime is however very far away from the continuous-wave working conditions of real-world lasers. Here we explore the possibility of achieving continuous-wave lasing in both CH₃NH₃PbI₃ and CH₃NH₃PbBr₃. Using an array of optical spectroscopy techniques, including femtosecond and nanosecond time-resolved photoluminescence, we measure the electronic temperature under stimulated emission conditions and test heating in the sample under both short and long laser pulse excitation conditions, meaning for exciting optical pulses much shorter and much longer than the photoluminescence lifetime. Time-resolved thermometry of the electron-hole gas demonstrates runaway heating phenomena caused by both the excess energy of exciting photons with respect to the bandgap and intrinsic non-radiative Auger recombination. Circumventing such limitations is possible by a choice of lattice temperature and laser excitation wavelength. We therefore demonstrate stimulated emission for transients as long as 100 ns at 200 K temperature.
Figure 1 | Quasi-steady-state stimulated emission in trihalide perovskite films. The photoluminescence was excited at different temperatures by 300-ns-long laser pulses with a repetition rate of 6 Hz and 2.35 eV photon energy. Panels a to d show time-integrated photoluminescence spectra of MAPbI3 (red lines) and MAPbBr3 (green lines) perovskites detected by a CCD camera; stimulated emission occurs at cryogenic temperatures (180 K), but disappears around 220K; in spite of a higher lasing threshold under fs excitation, the MAPbBr3 sample supports stimulated emission for higher temperatures than MAPbI3.

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