Abstract
In this paper we explain the temperature dependence of excitonic effective mass and charge carrier conduction mechanism occurs in CH3NH3PbI3−xClx thin films prepared by chemical dip coating (CDC), spray pyrolysis (Spray) and repeated dipping-withdrawing (Dipping). Hall Effect study confirmed that prepared CH3NH3PbI3−xClx samples are p-type semiconductor having carrier concentration of the order of ~ 1016 cm−3. The charge carrier mobility, mean free path and mean free life time were found to decrease with increasing temperature due to polaronic effect. The excitonic effective mass is estimated to (0.090–0.196)me and excitonic binding energy (15–33) meV, well consistent with Wannier-Mott hydrogenic model and the nature of exciton is likely to be Mott-Wannier type. From electrical measurement, it was observed that charge carrier conduction in CH3NH3PbI3−xClx is governed by migration of {mathrm{I}}^{-} and CH3N {mathrm{H}}_{3}^{+} vacancies and vacancy-assisted diffusion processes depending on temperature.
Highlights
In this paper we explain the temperature dependence of excitonic effective mass and charge carrier conduction mechanism occurs in CH3NH3PbI3−xClx thin films prepared by chemical dip coating (CDC), spray pyrolysis (Spray) and repeated dipping-withdrawing (Dipping)
When X site is replaced by another halogen element such as chlorine (Cl) into A MX3, it converts to mixed halide perovskites CH3NH3PbI3−xClx
In our previous work we report the characterization of nano-crystalline C H3NH3PbI3−xClx thin films prepared on glass substrate by chemical dipping-withdrawing (CDC)[2], spray pyrolysis (Spray)[5] and repeated dipping-withdrawing (Dipping)[3] techniques in an ambient atmosphere
Summary
In this paper we explain the temperature dependence of excitonic effective mass and charge carrier conduction mechanism occurs in CH3NH3PbI3−xClx thin films prepared by chemical dip coating (CDC), spray pyrolysis (Spray) and repeated dipping-withdrawing (Dipping). Multiple approaches such as transient terahertz (THz) s pectroscopy[6,12], combination of timeresolved terahertz with optical transient reflection spectroscopy (TRTS-TR)[13], photoluminescence quenching (PLQ)[14], time resolved electro-absorption spectroscopy[15], time-of-flight (TOF) photoconductivity[16] and Hall effect measurement[17] have been carried out to explore the transport properties of lead halide perovskites These pioneer studies reveal the presence of non-Langevin charge carriers[6], strong back-scattering on free carrier dynamics[12], existence of higher hole mobility compared to electron m obility[13], large electron–hole diffusion lengths (˃1 μm)[14], electric field assisted charge carrier s eperation[15], grain size dependent m obility[16], and influence of self-doping in carrier concentration[17]. The study of charge carrier dynamics is limited to tetragonal phase while it is important to explore such properties for cubic phase above room temperature (RT)
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