Search query: impedance solar cells

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abstract: Metal halide perovskites are mixed electronic ionic semiconductors with an extraordinarily rich optoelectronic behavior and the capability to function very efficiently as active layers in solar cells, with a record efficiency surpassing 23% nowadays. In this work, we carry out an impedance spectroscopy analysis of two perovskite solar cells with quite distinct optical and electrical characteristics, i.e. MAPbI3 and CsPbBr3 based devices. The main aim of the analysis is to establish how, regardless of the inherent complexity of the impedance spectrum due to ionic effects, information like ideality factors, recombination losses and the collection efficiency can be qualitatively and quantitatively assessed from impedance experiments under operating conditions.
author_names: Lidia Contreras-Bernal

Susana Ramos-Terron

Antonio J Riquelme

Pablo P Boix

Jesus Idigoras

Ivan Mora-Sero

Juan Antonio Anta
title: Impedance analysis of perovskite solar cells: a case study
year: 2019

abstract: We fabricated perovskite quantum dot solar cells (PQDSCs) and varied the thickness of the QD layer by controlling the number of deposition cycles; the cells were systematically investigated with impedance spectroscopy. Despite the evident structural differences with respect to standard perovskite solar cells (PSCs) similar impedance spectra were obtained for PQDSCs, pointing to similar working principles in terms of the active layer. We distinguish two different regimes: At low illumination, recombination is ruled by multiple trapping with trap distributions and/or shunting. However, at higher light intensities, Shockley Read Hall recombination is observed. In addition, the low frequency capacitance, CLF, of PQDSCs increases several orders of magnitude when the illumination is varied from dark to 1 sun conditions. This feature has not been observed in other kinds of photovoltaic devices and is characteristic of PSCs. Although there is no consensus about the exact mechanism responsible for CLF, the sugges.
author_names: Zahra Zolfaghari

Ehsan Hassanabadi

Didac Pitarch-Tena

Seog Joon Yoon

Zahra Shariatinia

Jao van de Lagemaat

Joseph M Luther

Ivan Mora-Sero
title: Operation Mechanism of Perovskite Quantum Dot Solar Cells Probed by Impedance Spectroscopy
year: 2019

abstract: Perovskite solar cells are notorious for exhibiting transient behaviour not seen in conventional inorganic semiconductor devices. Significant inroads have been made into understanding this fact in terms of rapid ion migration, now a well established property of the prototype photovoltaic perovskite MAPbI$_3$ and strongly implicated in the newer mixed compositions. Here we study the manifestations of ion migration in frequency domain small signal measurements, focusing on the popular technique of Electrical Impedance Spectroscopy (EIS) We provide new interpretations for a variety of previously puzzling features, including giant photo induced low frequency capacitance and negative capacitance in a variety of forms. We show that these apparently strange measurements can be rationalized by the splitting of AC current into two components, one associated with charge storage, and the other with the quasi steady state recombination current of electrons and holes. The latter contribution to the capacitance can take either a positive or a negative sign, and is potentially very large when slow, voltage sensitive processes such as ion migration are at play. Using numerical drift diffusion semiconductor models, we show that giant photo induced capacitance, inductive loop features, and low frequency negative capacitance all emerge naturally as consequences of ion migration via its coupling to quasi steady state electron and hole currents. In doing so, we unify the understanding of EIS measurements with the comparably well developed theory of rate dependent current voltage (I V) measurements in perovskite cells. Comparing the two techniques, we argue that EIS is more suitable for quantifying I V hysteresis than conventional methods based on I V sweeps, and demonstrate this application on a variety of cell types.
author_names: Daniel A Jacobs

Heping Shen

Florian Pfeffer

Jun Peng

Thomas P White

Fiona J Beck

Kylie R Catchpole Research School of Engineering

The Australian National University
title: The Two Faces of Capacitance: New Interpretations for Electrical Impedance Measurements of Perovskite Solar Cells and Their Relation to Hysteresis
year: 2018

abstract: Abstract The ubiquitous hysteresis in the current voltage characteristic of perovskite solar cells (PSCs) interferes in a proper determination of the diode ideality factor n a key parameter commonly adopted to analyze recombination mechanisms. An alternative way of determining n is by measuring the voltage variation of the ac resistances in conditions of negligible steady state dc currents. A reliable analysis of n based on the determination of the resistive response, free of hysteretic influences, reveals two separated voltage exponential dependences using different perovskite absorbers (3D perovskites layer based on CH3NH3PbI3 or mixed Cs0.1FA0.74MA0.13PbI2.48Br0.39) and a variety of interlayers (2D perovskite thin capping) The dominant resistive element always exhibits an exponential dependence with factor n 2 irrespective of the type of perovskite and capping layers. In addition, a non negligible resistive mechanism occurs at low frequencies (with voltage independent time constant 1 s) which is related to the kinetic properties of the outer interfaces, with varying ideality factor n 2 for CH3NH3PbI3, and n 1.5 for Cs0.1FA0.74MA0.13PbI2.48Br0.39) Our work identifies common features in the carrier recombination mechanisms among different types of high efficiency PSCs, and simultaneously signals particularities on specific architectures, mostly in the carrier dynamics at outer interfaces.
author_names: Osbel Almora

Kyung Taek Cho

Sadig Aghazada

Iwan Zimmermann

Gebhard J Matt

Christoph J Brabec

Mohammad Khaja Nazeeruddin

Germa Garcia-Belmonte
title: Discerning recombination mechanisms and ideality factors through impedance analysis of high efficiency perovskite solar cells
year: 2018

abstract: Mobile ions in hybrid perovskite semiconductors introduce a new degree of freedom to electronic devices suggesting applications beyond photovoltaics. An intuitive device model describing the interplay between ionic and electronic charge transfer is needed to unlock the full potential of the technology. We describe the perovskite contact interfaces as transistors which couple ionic charge redistribution to energetic barriers controlling electronic injection and recombination. This reveals an amplification factor between the out of phase electronic current and the ionic current. Our findings suggest a strategy to design thin film electronic components with large, tuneable, capacitor like and inductor like characteristics. The resulting simple equivalent circuit model, which we verified with time dependent drift diffusion simulations of measured impedance spectra, allows a general description and interpretation of perovskite solar cell behaviour.
author_names: Davide Moia

Ilario Gelmetti

Philip Calado

William Fisher

Michael Stringer

Onkar S Game

Yinghong Hu

Pablo Docampo

David G Lidzey

Emilio Jose Palomares

Jenny Nelson

Piers R F Barnes
title: Ionic to electronic current amplification in hybrid perovskite solar cells: ionically gated transistor interface circuit model explains hysteresis and impedance of mixed conducting devices
year: 2018

abstract: The partial replacement of methylammonium by formamidinium and cesium in organolead trihalide materials is of great importance to improve the performance and stability of photovoltaic solar cells. However, the effect of multiple cations on the cell functioning and their electrical characteristics remains to be clarified. By using the impedance spectroscopy technique, we have investigated the electrical response to a small ac perturbation applied to solar cells implementing hybrid perovskites with various compositions, polarized over a large potential range. The solar cell preparation protocols have been optimized to reach power conversion efficiencies higher than 17% The impedance response has been investigated both under light and in the dark to discriminate the light sensitive parameters. The spectra have been carefully analyzed using an ad hoc equivalent circuit, and the data have been discussed in the light of the existing literature. The spectra showed no intermediate frequency inductive loop due to.
author_names: Pengjiu Wang

Maria Ulfa

Thierry Pauporte
title: Effects of Perovskite Monovalent Cation Composition on the High and Low Frequency Impedance Response of Efficient Solar Cells
year: 2018

author_names: Didac Pitarch-Tena

Thi Tuyen Ngo

Marta Valles-Pelarda

Thierry Pauporte

Ivan Mora-Sero
title: Impedance Spectroscopy Measurements in Perovskite Solar Cells: Device Stability and Noise Reduction
year: 2018

abstract: Dye sensitized solar cells (DSCs) have emerged in the photovoltaic scenario as one of the most promising low cost alternative to the most employed solar devices based on silicon, especially for some niche application. Despite of the huge work carried out by scientists and researchers, detailed mechanism of some of the charge transfer processes occurring inside DSCs is not still fully understood. Electrochemical impedance spectroscopy (EIS) gave an immense help in analyzing these processes, and has been widely employed in the DSCs to characterize novel materials and architectures. The scope of this Review is to provide an insight on the application of EIS for the study of DSCs. A general introduction of the technique will be given, followed by an in depth review of its application in the DSC field. Finally, a brief discussion of future research directions concerning this topic will be presented.
author_names: Adriano Sacco
title: Electrochemical impedance spectroscopy: Fundamentals and application in dye sensitized solar cells
year: 2017

abstract: The analysis of perovskite solar cells by impedance spectroscopy has provided a rich variety of behaviors that demand adequate interpretation. Two main features have been reported: First, different impedance spectral arcs vary in combination; second, inductive loops and negative capacitance characteristics appear as an intrinsic property of the current configuration of perovskite solar cells. Here we adopt a previously developed surface polarization model based on the assumption of large electric and ionic charge accumulation at the external contact interface. Just from the equations of the model, the impedance spectroscopy response is calculated and explains the mentioned general features. The inductance element in the equivalent circuit is the result of the delay of the surface voltage and depends on the kinetic relaxation time. The model is therefore able to quantitatively describe exotic features of the perovskite solar cell and provides insight into the operation mechanisms of the device.
author_names: Elnaz Ghahremanirad

Agustin Bou

Saeed Olyaee

Juan Bisquert
title: Inductive Loop in the Impedance Response of Perovskite Solar Cells Explained by Surface Polarization Model.
venue: The journal of physical chemistry letters
year: 2017

abstract: Mesoscopic solid state solar cells based on the inorganic organic hybrid perovskite CH3NH3PbI3 in conjunction with the amorphous organic semiconductor spiro MeOTAD as a hole transport material (HTM) are investigated using impedance spectroscopy (IS) A model to interpret the frequency response of these devices is established by expanding and elaborating on the existing models used for the liquid and solid state dye sensitized solar cells. Furthermore, the influence of changing the additive concentrations of tert butylpyridine and LiTFSI in the HTM and varying the HTM overlayer thickness on top of the sub micrometer thick TiO2 on the extracted IS parameters is investigated. The internal electrical processes of such devices are studied and correlated with the overall device performance. In particular, the features in the IS responses that are attributed to the ionic and electronic transport properties of the perovskite material and manifest as a slow response at low frequency and an additional RC element at intermediate frequency, respectively, are explored.
author_names: Amalie Dualeh

Thomas Moehl

Nicolas Tetreault

Joel Teuscher

Peng Gao

Mohammad Khaja Nazeeruddin

Michael Gratzel
title: Impedance spectroscopic analysis of lead iodide perovskite sensitized solid state solar cells.
venue: ACS nano
year: 2014