Organometal Halide Perovskite Solar Cell Materials Rationalized: Ultrafast Charge Generation, High and Microsecond-Long Balanced Mobilities, and Slow Recombination

Abstract

Organometal halide perovskite-based solar cells have recently been reported to be highly efficient, giving an overall power conversion efficiency of up to 15%. However, much of the fundamental photophysical properties underlying this performance has remained unknown. Here, we apply photoluminescence, transient absorption, time-resolved terahertz and microwave conductivity measurements to determine the time scales of generation and recombination of charge carriers as well as their transport properties in solution-processed CH3NH3PbI3 perovskite materials. We found that electron-hole pairs are generated almost instantaneously after photoexcitation and dissociate in 2 ps forming highly mobile charges (25 cm(2) V(-1) s(-1)) in the neat perovskite and in perovskite/alumina blends; almost balanced electron and hole mobilities remain very high up to the microsecond time scale. When the perovskite is introduced into a TiO2 mesoporous structure, electron injection from perovskite to the metal oxide is efficient in less than a picosecond, but the lower intrinsic electron mobility of TiO2 leads to unbalanced charge transport. Microwave conductivity measurements showed that the decay of mobile charges is very slow in CH3NH3PbI3, lasting up to tens of microseconds. These results unravel the remarkable intrinsic properties of CH3NH3PbI3 perovskite material if used as light absorber and charge transport layer. Moreover, finding a metal oxide with higher electron mobility may further increase the performance of this class of solar cells.

Dynamic Stereochemical Activity of the Sn2+ Lone Pair in Perovskite CsSnBr3

“…[1][2][3][4][5][6][7] In addition to being investigated for use in radiation detectors and light emitting diodes, 8 the all-inorganic CsMX 3 (M = Ge, Sn, Pb; X = Cl, Br, I) perovskites offer an opportunity to understand the crystal chemistry of the divalent metal-halogen network without the added complexity introduced by the organic molecular ions present in the heavily studied organic-inorganic hybrids. [9][10][11][12] These materials are distinguished from tetrahedral semiconductors and from transition metal oxides in part by the presence of a s 2 lone pair on the divalent M-site cation.…”

Defect Dynamics in Proton Irradiated CH3NH3PbI3 Perovskite Solar Cells

“…high efficient solar cells [4,5] , photo-capacitors and piezoelectric sensors [6] , memristors [7] , etc.…”

High Performance Perovskite Solar Cells

“…Nevertheless, the PCEs of these solar cells are mostly poor (≈10%–12%) to date, primarily owing to imperfect device fabrication, low light absorbing efficiency and unexpected charge recombination 2. Holding promise for addressing these problems, novel perovskite materials based on organometal halide CH3NH3PbX3 (CH3NH3 + = MA, X = I, Cl and Br)3 are developed and their suitable attributes for solar cells including strong light absorption, bipolar transporting abilities, balanced electron and hole diffusion lengths, lower charge recombination and facile fabrication are demonstrated as well 4. Solar cells utilizing these perovskite materials (i.e., perovskite solar cells) have emerged as a rising star since being first investigated by Miyasaka and his colleagues in 2009, who employed perovskite material as a sensitizer in liquid‐dye‐sensitized solar cells and demonstrated a relatively low PCE of around 3.8% 5.…”