N and p-type properties in organo-metal halide perovskites studied by Seebeck effects

• Changing composition can tune Seebeck coefficient between positive and negative values.
• Varying composition can tune semiconducting properties between n and p-type regimes.
• Internal polarization is responsible for large temperature-dependent Seebeck effects.

Organo-metal halide perovskites can exhibit co-existed electrical polarizations and semiconducting properties respectively from organic and inorganic components. Here, we find that the Seebeck coefficient can be changed between positive and negative values when the concentration of chloride ions is varied between single-halide (CH3NH3PbI3) and mixed-halide structures (CH3NH3PbIxCl3−x). This indicates that varying the concentration of chloride ions can tune the semiconducting properties between the n-type and p-type regimes in the organo-metal halide perovskites. Our temperature-dependent capacitance measurement shows that increasing temperature can cause a change on internal electrical polarization. As a result, we can propose that the internal polarization functions as the underlying mechanism responsible for large temperature-dependent Seebeck coefficients in organo-metal halide perovskites operating between n-type and p-type regimes.

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