Assessing Temperature Dependence of Drift Mobility in Methylammonium Lead Iodide Perovskite Single Crystals

Hybrid organic–inorganic perovskites have emerged as cost-effective and high-performance semiconductors for optoelectronic applications. Precise knowledge of charge carrier mobility and especially the temperature dependence of mobility is therefore of utmost relevance for advancing high-performance materials. Here, the charge carrier mobility in methylammonium lead iodide single crystals is investigated with time of flight technique from 290 to 100 K. A nondispersive transport with an electron mobility of 135 (±20) cm²/V s and a hole mobility of 90 (±20) cm²/V s is obtained at room temperature. A power-law temperature dependence of mobility, μ ∝ <i>T</i>^<i>m</i>, with an exponent <i>m</i> = −2.8 and −2.0, is measured for electrons and holes in the tetragonal phase. The highest electron and hole mobilities measured are 635 (±70) and 415 (±20) cm²/V s, respectively. Our results indicate that the scattering of charge carriers with phonons is the limiting factor for carrier mobilities at room temperature

Persistent Energetic Electrons in Methylammonium Lead Iodide Perovskite Thin Films

In conventional semiconductor solar cells, carriers are extracted at the band edges and the excess electronic energy (<i>E*</i>) is lost as heat. If <i>E</i>* is harvested, power conversion efficiency can be as high as twice the Shockley–Queisser limit. To date, materials suitable for hot carrier solar cells have not been found due to efficient electron/optical-phonon scattering in most semiconductors, but our recent experiments revealed long-lived hot carriers in single-crystal hybrid lead bromide perovskites. Here we turn to polycrystalline methylammonium lead iodide perovskite, which has emerged as the material for highly efficient solar cells. We observe energetic electrons with excess energy ⟨<i>E*</i>⟩ ≈ 0.25 eV above the conduction band minimum and with lifetime as long as ∼100 ps, which is 2–3 orders of magnitude longer than those in conventional semiconductors. The energetic carriers also give rise to hot fluorescence emission with pseudo-electronic temperatures as high as 1900 K. These findings point to a suppression of hot carrier scattering with optical phonons in methylammonium lead iodide perovskite. We address mechanistic origins of this suppression and, in particular, the correlation of this suppression with dynamic disorder. We discuss potential harvesting of energetic carriers for solar energy conversion