Illumination Intensity Dependence of the Recombination Mechanism in Mixed Perovskite Solar Cells

Abstract

Recombination mechanisms in solar cells are frequently assessed through the determination of ideality factors. In this work we report an abrupt change of the value of the “apparent” ideality factor (nAP) in high‐efficiency FA0.71MA0.29PbI2.9Br0.1 based mesoscopic perovskite solar cells as a function of light intensity. This change is manifested as a transition from a regime characterized by nAP∼1.8–2.5 at low light intensities (<10 mWcm‐2) to one characterized by nAP∼1. This transition is equally observed in the recombination resistance extracted from open‐circuit impedance measurements. We use drift‐diffusion simulations with explicit consideration of ion migration to determine the origin of this transition. We find that a change ofrecombination mechanism concurrent with a modification of the concentration of ionic vacancies is the most likely explanation of the observed behaviour. In the drift‐diffusion simulations we show that the apparent ideality factor is in fact affected by the ion vacancy concentration so it is not the optimal parameter to assess the dominant recombination mechanism. We argue that a procedure based on a recently derived “electronic” ideality factor obtained from the high frequency feature of the impedance spectrum is better suited to determine the recombination route that dictates the photovoltage.

Ultrathin Plasma Polymer Passivation of Perovskite Solar Cells for Improved Stability and Reproducibility

“…According to previous works, the change in the β parameter suggests a different main recombination mechanism inside of the PSC, although some ionic effects cannot be ruled out. [ 29,34 ] On the other hand, Figure S5, Supporting Information, shows that the high‐frequency capacitance is also not significantly altered by the presence of Adamantane interlayer.…”

Degradation Analysis of Triple-Cation Perovskite Solar Cells by Electrochemical Impedance Spectroscopy

“…For the sake of clarity, we differentiate this ideality factor from other solar cells, where it is just determined by electron dynamics. Hereafter, we will call “ m ” the apparent ideality factor of PSCs. ,, The ideality factor can be related to the recombination mechanism . Also, it has been recently used to track the performance of PSCs outdoors …”

“…Hereafter, we will call "m" the apparent ideality factor of PSCs. 40,48,49 The ideality factor can be related to the recombination mechanism. 50 Also, it has been recently used to track the performance of PSCs outdoors.…”

Impact of non-stoichiometry on ion migration and photovoltaic performance of formamidinium-based perovskite solar cells

“…In recent work it has been shown that ionic features can also affect the recombination parameters and complicate the interpretation of the impedance spectrum and the ideality factor. 22,26,30,56 Recently, Bennett and coworkers 30 have proposed an “electronic” ideality factor which is not “contaminated” by the ionic properties of the sample. This quantity is calculated via where q is the elementary charge, R hf is the high frequency resistance described before and J rec the DC recombination current.…”

“…Photovoltaic performance in PSC is also strongly dependent on recombination kinetics. Charge collection efficiencies are determined by the interplay between recombination in the bulk and at the interfaces [19][20][21][22] and the internal electric eld created by ion migration and ion accumulation at the interfaces. [23][24][25][26] Thus, electronic recombination and ion motion phenomena are linked to each other in PSC under operation.…”