Influence of organic cations on high-performance CH 3 NH 3 PbI 3 based photovoltaics

Addressing the Reliability and Electron Transport Kinetics in Halide Perovskite Film via Pulsed Laser Engineering

“…Time‐resolved photoluminescence (TRPL) spectra is measured under different scanning speed for MAPbI 3 thin films on glass slide, as shown in Figure a. To investigate the carrier kinetics in the MAPbI 3 perovskite film, the TRPL pattern is fitted by a 2‐constant exponential decay function where A 1 is the intensity for exciton–exciton annihilation, A 2 is the intensity for excitons, τ 1 and τ 2 are carrier lifetimes, corresponding to exciton–exciton annihilation and radiative recombination. When the scanning speed is decreased from 500 to 300 mm s −1 , both τ 1 and τ 2 are increasing, when the scanning speed further decreases to 100 mm s −1 , the carrier lifetimes turn to decrease (Figure b).…”

“…Such carrier density change is also an evidence of Fermi level shifts, verifying that the perovskite film undergoes transition between n‐type and p‐type characters, and the Fermi level is closer to the medium of the bandgap under 300 mm s −1 scanning speed. Since the carrier concentration and the carrier mobility are inversely related by the formula µ = 1/ neρ , the carrier mobility also reaches a maximum at the scanning speed of 300 mm s −1 . Parasitic resistance is also a major factor affecting the photoelectric performance of perovskite, which is mainly divided into series resistance and shunt resistance.…”

“…As a result, larger crystal size with higher crystalline quality under 300 mm s −1 laser scanning speed can induce higher electronic performances. In addition, the d‐spacing along (110) direction is also calculated from XPS spectra based on the Bragg diffraction Equation . With increasing laser scanning speed, the d‐spacing presents a slightly decreasing trend and then saturates due to the laser‐induced movement of ions across the thin film, which indicates that the PbI bond strength of the perovskite film gradually weakens as the scanning speed decreases, thus the band structure of perovskite film can be modulated.…”

CH3NH3PbI3: precise structural consequences of water absorption at ambient conditions

“…Organic-inorganic hybrid perovskite CH 3 NH 3 PbI 3 (MAPbI 3 ) is currently under precise investigation owing to its application in solar cells (Kojima et al, 2009;Im et al, 2011;Service, 2013;Snaith, 2013;Grä tzel, 2014;Spina et al, 2015;Bi et al, 2016;Chang et al, 2016;Hodes & Cahen, 2014). The crystal structure of this compound contains a methyl ammonium (MA + ) cation, [H 3 C-NH 3 ] + , in the cuboctahedral interstices of the framework formed by [PbI 6 ] octahedra.…”

Controlled crystallization of CH3NH3PbI3 films for perovskite solar cells by various PbI2(X) complexes

“…Firstly, the basic film processing parameters have been investigated by tuning the annealing temperature [20][21][22][23] and time [21], spin-coating rate [24], the atmospheric conditions [25,26], or by employing different solvents [22,27,28] or additives [29][30][31][32][33]. Secondly, the starting materials including inorganic lead source and organic ammonia salt have been found to determine the perovskite crystal growth kinetics, which in turn affects the film morphology and device performance [34][35][36][37][38][39][40]. Recently, a stable complex of methyl ammonia iodide or bromide (MAI(Br)), lead iodide or bromide (PbI(Br) 2 ) and dimethyl sulfoxide (DMSO) was demonstrated to be a decisive factor in retarding the rapid reaction between MAI(Br) and PbI(Br) 2 in a solvent engineering method, which enabled the formation of a highly uniform and dense film [41][42][43].…”