Accessing the conduction band dispersion in CH3NH3PbI3 single crystals

TL;DR

This study investigates the conduction band structure of CH3NH3PbI3 single crystals using advanced spectroscopic techniques, revealing dispersion characteristics, effective mass, and surface effects relevant for optoelectronic applications.

Contribution

It provides the first direct experimental observation of conduction band dispersion in CH3NH3PbI3 using AR-2PPE and AR-LEIPS, confirming theoretical predictions and highlighting electron correlation effects.

Findings

Conduction band shows clear dispersion along the ΓM direction.

Effective electron mass at Γ point is approximately 0.20m0 at 90 K.

Surface structure maintains cubic-like electronic properties at lower temperatures.

Abstract

The conduction band structure in methylammonium lead iodide (CH3NH3PbI3) was studied both by angle-resolved two-photon photoemission spectroscopy (AR-2PPE) with low-photon intensity and angle-resolved low-energy inverse photoelectron spectroscopy (AR-LEIPS). Clear energy dispersion of the conduction band along the {\Gamma}M direction was observed by these independent methods under different temperatures, and the dispersion was found to be consistent with band calculations under the cubic phase. The effective mass of the electrons at the {\Gamma} point was estimated to be (0.20+-0.05)m0 at 90 K. The observed energy position was largely different between the AR-LEIPS and AR-2PPE, demonstrating the electron correlation effects on the band structures. The present results also indicate that the surface structure in CH3NH3PbI3 provides the cubic-dominated electronic property even at lower temperatures.