Nature of the different emissive states and strong exciton-phonon couplings in quasi-two-dimensional perovskites derived from phase-modulated two-photon micro-photoluminescence spectroscopy.

Quasi two-dimensional perovskites have attracted great attention for applications in light-emitting devices and photovoltaics due to their robustness and tunable highly efficient photoluminescence (PL). However, the mechanism of intrinsic PL in these materials is still not fully understood. In this work, we have analysed the nature of the different emissive states and the impact of temperature on the emissions in quasi two-dimensional methyl ammonium lead bromide perovskite (q-MPB) and cesium lead bromide perovskite (q-CPB).

Ultrafast polaron-pair dynamics in a poly(3-hexylthiophene-2,5-diyl) device influenced by a static electric field: insights into electric-field-related charge loss.

The generation and decay mechanisms of polaron pairs in organic semiconductor-based optoelectronic devices under operational conditions are relevant for a better understanding of photophysical processes affecting the device performance, since the possible occurrence of a polaron pair introduces an intermediate step in exciton dissociation into fully separated charge carriers. The role played by static electric fields in polaron-pair dynamics is important but poorly understood or not investigated in detail. In this work, insights into the polaron-pair dynamics in neat poly(3-hexylthiophene-2,5-diyl) (P3HT) thin films and P3HT films sandwiched between electrical contacts with an applied external static electric field are probed using femtosecond pump-probe transient absorption spectroscopy.

Influence of the alkyl side-chain length on the ultrafast vibrational dynamics of 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide (CmimNTf) ionic liquids.

Probing the vibrational dynamics of 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide (CmimNTf) ionic liquids (ILs) using femtosecond time-resolved coherent anti-Stokes Raman scattering (fs-CARS) has indicated the ultrafast vibrational energy transfer between counter ions which is governed by interionic interactions and facilitated by hydrogen bonds. In this study, fs-CARS is used to investigate the ultrafast dynamics of the vibrational modes of the CmimNTf ILs with n = 6, 8, 10, and 12 in a spectral region, which involves the imidazolium ring and the alkyl side-chain vibrations. The vibrational Raman modes with wavenumbers around 1418 cm are excited through the CARS process and the ultrafast time evolution of the consequently excited vibrational modes is monitored.