Magnetic field e ects have been a successful tool for studying carrier dynamics in organic semiconductors as the weak spin-orbit coupling in these materials gives rise to long spin relaxation times. As the spin-orbit coupling is strong in organic-inorganic hybrid perovskites, which are promising materials for photovoltaic and light-emitting applications, magnetic field e ects are expected to be negligible in these optoelectronic devices. We measured significant magneto-photocurrent, magneto-electroluminescence and magneto-photoluminescence responses in hybrid perovskite devices and thin films, where the amplitude and shape are correlated to each other through the electron-hole lifetime, which depends on the perovskite film morphology. We attribute these responses to magnetic-field-induced spin-mixing of the photogenerated electron-hole pairs with di erent g-factors-the g model. We validate this model by measuring large g (∼ 0.65) using field-induced circularly polarized photoluminescence, and electron-hole pair lifetime using picosecond pump-probe spectroscopy.T he organic-inorganic hybrid perovskites (CH 3 NH 3 PbX 3 , X = halogen; Fig. 1a) have attracted an immense interest recently as an excellent candidate for photovoltaic solar cells 1-7 . Record power conversion efficiency (PCE) of 19.3% has been achieved in optimized devices with a finely grown perovskite active layer 8 . It has been shown that the perovskites have a large absorption coefficient in the visible-near-infrared spectral range, and high charge carriers' photogeneration efficiency 9-11 ; both properties are excellent for photovoltaic applications. Interestingly, the same hybrid perovskites show photoluminescence (PL) emission ( Fig. 1b), laser action 12 and electroluminescence (EL) in lightemitting diodes 13 (LEDs). However, the underlying photophysics of the efficient charge photogeneration for photovoltaic applications, and the mechanism of radiative charge recombination that is required for LED applications are not yet clear 14,15 . In particular the perovskite layer consists of many tiny crystalline domains, where the natural disorder may encourage the formation of relatively long-lived spin-1/2 electron-hole (e-h) pairs 16 . Consequently, the generation and recombination of these spin-pair species may be influenced by a magnetic field.The magnetic field effect (MFE) technique has been a powerful tool for studying spin-dependent generation and recombination processes of spin-pair species in carbon-based semiconductor film devices 17,18 . In this technique the applied magnetic field, B, modulates the outcome physical quantity in the optoelectronic device, in the form of magneto-conductivity (MC) and magnetophotoconductivity (MPC) in organic photovoltaic cells 19 , magnetoelectroluminescence (MEL) in organic LEDs (ref. 20), and magnetophotoluminescence (MPL) in pristine films 21 . This occurs because B changes the spin sublevels character in the spin-pair manifold; which, in turn changes the inter-sublevels spin-mixing rates that consequently ...

The nature of the primary photoexcitations in semiconducting single-walled carbon nanotubes ͑S-SWCNTs͒ is of strong current interest. We have studied the emission spectra of S-SWCNTs and two different -conjugated polymers in solutions and films, and have also performed ultrafast pump-probe spectroscopy on these systems with unprecedented spectral range from 0.1 to 2.6 eV. The emission spectra relative to the absorption bands are very similar in S-SWCNTs and polymers, with redshifted photoluminescence in films showing exciton migration. We also found that the transient excited state spectra of both polymers and SWCNTs contain two prominent photoinduced absorption ͑PA͒ bands ͑PA 1 and PA 2 ͒ that are due to photogenerated excitons; in the polymers these PA bands are correlated with a stimulated emission band, which is absent in the S-SWCNTs. In order to understand the similarities in the PA spectra we have performed theoretical calculations of excited state absorptions in -conjugated polymers as well as S-SWCNTs within the same correlated electron Hamiltonian. We find strong similarities in the excitonic energy spectra of these two classes of quasi-one-dimensional materials, although there exist also subtle differences such as the occurrence of dark excitons below the optical excitons in the S-SWCNTs. In the polymers PA 1 is an excited state absorption from the optical exciton to a two-photon exciton that occurs below the continuum band threshold. In the S-SWCNTs PA 1 occurs from both the optical exciton and the dark exciton, to final states which are close in energy and again below the continuum band threshold. PA 1 therefore gives the lower limit of the binding energy of the lowest optical exciton in both -conjugated polymers and S-SWCNTs. The binding energy of lowest exciton that belongs to the widest S-SWCNTs with diameters ജ1 nm in films is 0.3-0.4 eV, as determined by both experimental and theoretical methods.

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