Abstract
Organic-inorganic perovskite as a promising candidate for solar energy harvesting has attracted immense interest for its low-cost preparation and extremely high quantum efficiency. However, the fundamental understanding of the photophysics in perovskite remains elusive. In this work, we have revealed two distinct states in MAPbI3 thin films at low temperature through time-resolved photoluminescence spectroscopy (TRPL). In particular, we observed a photo-induced carrier injection from the high energy (HE) state to the low energy (LE) state which has a longer lifetime. The strong interaction between the two states, evidenced by the injection kinetics, can be sensitively controlled through the excitation power. Understanding of the interacting two-states not only sheds light on the long PL lifetime in perovskite but also helps to understand the different behavior of perovskite in response to different excitation power. Further efforts in modifying the low energy state could significantly improve the quantum efficiency and lead to novel application in optoelectronics based on perovskite.
Highlights
Communication to the low energy (LE) state of longer lifetime for temporary storage
We prepared the MAPbI3 thin film using the spin-coating method and the polycrystalline film was deposited on a silicon wafer with 300 nm thermal oxide[24,25]
We first characterized the film in PL at room temperature and 77 K under 2.33 eV (λ = 532 nm) continuous wave (CW) laser excitation with an excitation power of 1 μW (Fig. 1a)
Summary
Communication to the LE state of longer lifetime for temporary storage. Upon high excitation power, the LE state exhibits a saturation behavior and the response of the perovskite is found to be dominated by the HE state. Peak B (blue, 77 K) behaves distinctively different in that the rise after the excitation pulse occurs asymptotically with a delay on the time scale of hundreds of picoseconds. To explore the rising delay of peak B in TRPL, we varied the excitation fluence (Fig. 2).
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