Charge‐Carrier Dynamics, Mobilities, and Diffusion Lengths of 2D–3D Hybrid Butylammonium–Cesium–Formamidinium Lead Halide Perovskites

Abstract

Perovskite solar cells (PSCs) have improved dramatically over the past decade, increasing in efficiency and gradually overcoming hurdles of temperature-and humidity-induced instability. Materials that combine high charge-carrier lifetimes and mobilities, strong absorption, and good crystallinity of 3D perovskites with the hydrophobic properties of 2D perovskites have become particularly promising candidates for use in solar cells. In order to fully understand the optoelectronic properties of these 2D-3D hybrid systems, the hybrid perovskite BA x (FA 0.83 Cs 0.17 ) 1-x Pb(I 0.6 Br 0.4 ) 3 is investigated across the composition range 0 ≤ x ≤ 0.8. Small amounts of butylammonium (BA) are found that help to improve crystallinity and appear to passivate grain boundaries, thus reducing trap-mediated chargecarrier recombination and enhancing charge-carrier mobilities. Excessive amounts of BA lead to poor crystallinity and inhomogeneous film formation, greatly reducing effective charge-carrier mobility. For low amounts of BA, the benevolent effects of reduced recombination and enhanced mobilities lead to charge-carrier diffusion lengths up to 7.7 µm for x = 0.167. These measurements pave the way for highly efficient, highly stable PSCs and other optoelectronic devices based on 2D-3D hybrid materials.

Correlating Phase Behavior with Photophysical Properties in Mixed‐Cation Mixed‐Halide Perovskite Thin Films

“…Buizza et al [57] recently presented an analytical solution to this modified form of the rate equation, which is as follows …”

Toward Real Setting Applications of Organic and Perovskite Solar Cells: A Comparative Review

“…The main distinguishing characteristics of hybrid perovskites are: 1) low electron and hole effective masses [ 45 ] ; 2) high carrier mobility of both electron and holes (13–15 cm 2 V −1 s −1 ); [ 46 ] 3) long carrier lifetime (on the order of tenths of μs); [ 47 ] 4) high charge carrier diffusion length (>μm) [ 46 ] ; 5) ambipolar behavior with good charge carrier separation; 6) tunable direct bandgap (1.47–2 eV); [ 48 ] 7) large absorption coefficient (1.5 × 10 5 cm −1 ); [ 48 ] 8) high dielectric constant (60 at low frequency); [ 49,50 ] and 9) low exciton binding energy (few meV). [ 45 ]…”

“…The physical properties of hybrid perovskites make this class of materials striking for many optoelectronic devices, not only for solar cells, but also for high-performance LEDs. [44] The main distinguishing characteristics of hybrid perovskites are: 1) low electron and hole effective masses [45] ; 2) high carrier mobility of both electron and holes (13-15 cm 2 V À1 s À1 ); [46] 3) long carrier lifetime (on the order of tenths of μs); [47] 4) high charge carrier diffusion length (>μm) [46] ; 5) ambipolar behavior with good charge carrier separation; 6) tunable direct bandgap (1.47-2 eV); [48] 7) large absorption coefficient (1.5 Â 10 5 cm À1 ); [48] 8) high dielectric constant (60 at low frequency); [49,50] and 9) low exciton binding energy (few meV). [45] While the large absorption coefficient of perovskites ensures the possibility to work with thin active films, low exciton binding energy, high dielectric constant, high mobility, long lifetime, diffusion length of charge carriers, and ambipolar behavior of perovskites are the essential ingredients for an efficient generation, transport, and collection of photogenerated carriers at the electrodes of the solar cells.…”

Stimuli‐Enabled Artificial Synapses for Neuromorphic Perception: Progress and Perspectives

“…Perovskites are promising alternative candidate materials for memory applications because of their ambipolar charge transport [56,57] properties and their long charge carrier diffusion lengths. [58][59][60] In perovskite-based memristors, dynamic ion migration related to the device current-voltage hysteresis has been considered as a basic form for data storage. [42,61,62] Xu et al [63] investigated the ionic migration mechanism in an organometeal halide perovskite (OHP) artificial synapse.…”