Temperature-Dependent Ambipolar Charge Carrier Mobility in Large-Crystal Hybrid Halide Perovskite Thin Films

Abstract

Perovskite-based thin-film solar cells today reach power conversion efficiencies of more than 22%. Methylammonium lead iodide (MAPI) is prototypical for this material class of hybrid halide perovskite semiconductors and at the focal point of interest for a growing community in research and engineering. Here, a detailed understanding of the charge carrier transport and its limitations by underlying scattering mechanisms is of great interest to the material’s optimization and development. In this article, we present an all-optical study of the charge carrier diffusion properties in large-crystal MAPI thin films in the tetragonal crystal phase from 170 K to room temperature. We probe the local material properties of individual crystal grains within a MAPI thin film and find a steady decrease of the charge carrier diffusion constant with increasing temperature. From the resulting charge carrier mobility, we find a power law dependence of μ ∝ T m with m = −(1.8 ± 0.1). We further study the temperature-dependent mobility of the orthorhombic crystal phase from 50 to 140 K and observe a distinctly different exponent of m = −(1.2 ± 0.1).

Space-charge-limited electron and hole currents in hybrid organic-inorganic perovskites

“…We obtain a mobility of 1.2 × 10 −6 m 2 V −1 s −1 for electrons and 3.5 × 10 −10 m 2 V −1 s −1 for holes. We note that our extracted mobilities are comparable to values obtained by electrode-based mobility measurement techniques 31,40,43,64,65 and lower than the ones obtained by electrode-free techniques 27,28,31 . We note that the large variation in reported mobilities is likely the result of differences in sample morphologies, measurement techniques (e.g., different timescales), and their interpretation.…”

“…The accurate agreement between our experiments and simulations, based on experimentally determined parameters, demonstrates that the SCLC behavior in perovskites is completely governed by the temperature dependence of ion dynamics and the associated temperature and frequency-dependent permittivity. We note that temperature-dependent mobilities have been reported using different techniques, but in all cases the frequency and temperature dependence of permittivity due to ion dynamics were not taken into account in the interpretation of the data 24 , 28 , 29 , 53 , 64 , 65 , 69 – 72 . We cannot fully exclude a very small temperature dependence of the charge-carrier mobility but, if present, is fully overwhelmed by the temperature dependence of the permittivity and therefore of no relevance for the description of the SCLC.…”

“…One particularly important aspect in understanding the behavior of perovskite-based electronic devices is the characterization of the transport of electronic charges. Over recent years, many techniques have been employed to measure the charge-carrier mobility in perovskites [19][20][21][22][23][24][25][26][27][28][29][30] , giving a vast range of different numbers 31,32 . The large differences observed in the measured charge-carrier mobility may, in part, be the result of different perovskite formulations and processing conditions, resulting in different film morphologies.…”

Recent progress of graphene‐based materials for efficient charge transfer and device performance stability in perovskite solar cells

“…The organic‐inorganic hybrid perovskite includes semiconductor of CH 3 NH 3 PbI 3 , CH 3 NH 3 PbBr 3 , and the mixed halide form CH 3 NH 3 PbI 3–x Cl x or CH 3 NH 3 PbI 3–x Br x are the most common perovskite material frequently used for solar cell applications. The benefits of this class of materials as an active absorber layer include minimizing recombination losses, 121 low costs of material, 122 long charge carrier diffusion distances, 123 and the potential of cation and anion replacement for tuning the energy band 124 . Despite having promising advantages, PSCs also encounter several drawbacks to meet high efficiency, large‐scale production, low‐cost materials and procedures, and also high stability devices 125 .…”

Enhanced Selective Charge Collection with Metal–Insulator–Semiconductor Junction in Electron Transport Layer‐Free Perovskite Solar Cells

“…With their unique properties such as high light absorptivity, long and balanced charge diffusion lengths, [ 1–3 ] and ambipolar charge transport, [ 4,5 ] halide perovskites have drawn intense attention in recent years. Since the first report on perovskite solar cell (PSC) in 2009, [ 6 ] a sharp upswing of power conversion efficiency (PCE) to over 25.5% has been achieved, [ 7 ] which is adequate for commercial applications.…”