Search query: Admittance SpectroscopyAutoencoder

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abstract: Thermal admittance spectroscopy (TAS) is frequently used to analyze the properties of trap states in semiconductor devices. We perform detailed simulations in combination with experiments to understand the effect of low carrier mobility on the analysis of trap states by TAS. We show that the apparent characteristic peak in the differential capacitance spectra is strongly dominated by the dielectric relaxation (DR) peak caused by low carrier mobilities for the case of shallow traps and low trap densities. The model for the DR dominated case is successfully applied to interpret the experimental results from poly(3 hexylthiophene 2,5 diyl) (P3HT) based diodes. In contrast, for deep states with high density of states, we are able to properly estimate the energetic position, but the low carrier mobility affects the correct determination of the attempt to escape frequency as well as the capture cross section. Our results reveal that low carrier mobilities cause inherent obstacles in accurately determining the t.
author_names: Shuo Wang

Pascal Kaienburg

Benjamin Klingebiel

Diana Schillings

Thomas Kirchartz
title: Understanding Thermal Admittance Spectroscopy in Low Mobility Semiconductors
year: 2018

abstract: Abstract CdTe solar cells have recently reached its highest conversion efficiencies, comparable to CuInGaSe 2 and Si devices. One of the key factors for the success of these devices is the so called "activation" treatment, which typically consists in depositing a CdCl 2 film on the CdTe absorber layer and in a subsequent annealing in air or nitrogen atmosphere. Nevertheless CdCl 2 is a carcinogenic and water soluble compound; for this reason recent studies have found MgCl 2 as a good alternative. In this work we have studied devices (exceeding 14% efficiency) prepared by low substrate temperature CdTe deposition and activated with MgCl 2 treatment (applied by wet deposition) The devices were characterized by means of current voltage, capacitance voltage, drive level capacitance profiling and admittance spectroscopy techniques. Carrier concentration and also concentration and distribution of shallow and deep defects are presented and compared with data obtained from analogous devices but activated with the standard CdCl 2 Despite CdTe layers treated with the two different processes exhibit similar structural properties, the distribution of deep and shallow defects results to be different and moreover admittance spectroscopy technique reveals the presence of different defects, at 344 and 358 meV, which are present only in MgCl 2 treatment case.
author_names: Daniele Menossi

Elisa Artegiani

Andrei Salavei

Simone Di Mare

Alessandro Romeo
title: Study of MgCl2 activation treatment on the defects of CdTe solar cells by capacitance voltage, drive level capacitance profiling and admittance spectroscopy techniques
year: 2017

abstract: Admittance spectroscopy is a useful tool used to study defects in semiconductor materials. However, metastable defect responses in non ideal semiconductors can greatly impact the measurement and therefore the interpretation of results. Here, admittance spectroscopy was performed on Cu2ZnSn(S,Se)4 where metastable defect response is illustrated due to the trapping of injected carriers into a deep defect state. To investigate the metastable response, admittance measurements were performed under electrically and optically relaxed conditions in comparison to a device following a low level carrier injection pretreatment. The relaxed measurement demonstrates a single capacitance signature while two capacitance signatures are observed for the device measured following carrier injection. The deeper level signature, typically reported for kesterites, is activated by charge trapping following carrier injection. Both signatures are attributed to bulk level defects. The significant metastable response observed on kes.
author_names: Mark J Koeper

Charles J Hages

Jian V Li

Dean Howard Levi

Rakesh Agrawal
title: Metastable defect response in CZTSSe from admittance spectroscopy
year: 2017

abstract: The introduction of Cl into CH3NH3PbI3 precursors is reported to enhance the performance of CH3NH3PbI3 solar cell, which is attributed to the significantly increased diffusion lengths of carriers in CH3NH3Pb(I,Cl)3 solar cell. It has been assumed but never experimentally approved that the defect density in CH3NH3Pb(I,Cl)3 solar cell should be reduced according to the higher carrier lifetime observed from photoluminescence (PL) measurement. We have fabricated CH3NH3Pb(I,Cl)3 solar cell by adding a small amount of Cl source into CH3NH3PbI3 precursor. The performance of CH3NH3Pb(I,Cl)3 solar cell is significantly improved from 15.39% to 18.60% Results from scanning electron microscopy and X ray diffraction indicate that the morphologies and crystal structures of CH3NH3PbI3 and CH3NH3Pb(I,Cl)3 thin films remain unchanged. Open circuit voltage decay and admittance spectroscopy characterization jointly approve that Cl plays an extremely important role in suppressing the formation of defects in perovskite solar cells.
author_names: Minlin Jiang

Fei Lan

Bingxin Zhao

Quan Tao

Jiamin Wu

Di Gao

Guangyong Li
title: Observation of lower defect density in CH3NH3Pb(I,Cl)3 solar cells by admittance spectroscopy
year: 2016

abstract: Abstract Heat light soaking effects on Cu(In,Ga)Se2 (CIGS) solar cells with atomic layer deposition (ALD) Zn(O,S) and chemical bath deposition (CBD) ZnS(O,OH) buffer layers were investigated using temperature dependent current voltage and admittance spectroscopy measurements. Both CBD ZnS(O,OH)/CIGS and ALD Zn(O,S)/CIGS solar cells showed a significant increase in the cell performance after the combined heat and light soaking (HLS) post treatment. Temperature dependent current voltage measurements showed a reduced roll over of current density voltage curve after the HLS post treatment, suggesting a reduced recombination at the absorber/buffer interface. Admittance spectroscopy measurement revealed a remarkable shift towards shallower energy positions for the defect N1 after HLS post treatment in both CIGS solar cells fabricated using CBD and ALD methods. By optimizing the HLS and the deposition conditions for each buffer layer, CBD ZnS(O,OH)/CIGS and ALD Zn(O,S)/CIGS solar cells yielded total efficiencies of 18.8 and 18.7% respectively.
author_names: Taizou Kobayashi

Zacharie Jehl Li Kao

Tokio Nakada
title: Temperature dependent current voltage and admittance spectroscopy on heat light soaking effects of Cu(In,Ga)Se2 solar cells with ALD Zn(O,S) and CBD ZnS(O,OH) buffer layers
year: 2015

abstract: Abstract Thanks to their strong absorption in the near infrared, squaraine dyes have raised interest in the field of organic photovoltaics and photodetection. We develop photodetectors based on the bulk heterojunction of an indolic squaraine and of a fullerene derivative, obtaining an external quantum efficiency as high as 12% at 590 nm. To gain insight into carrier transport and recombination phenomena, devices are characterized in the dark by means of admittance spectroscopy. At low applied voltages carrier transport is dominated by holes, which show dispersive transport and an electric field dependent mobility of about 10 5 10 4 cm2 V 1 s 1. At higher voltages electron injection occurs as well and a bipolar, recombination limited regime sets in. The modeling of the low frequency negative capacitance contribution suggests a trap mediated carrier recombination mechanism.
author_names: Sebastiano Bellani

Antonio Iacchetti

Matteo Porro

Luca Beverina

Maria Rosa Antognazza

Dario Natali
title: Charge transport characterization in a squaraine based photodetector by means of admittance spectroscopy
year: 2015

abstract: Precision admittance spectroscopy measurements over wide temperature and frequency ranges were carried out for chemical vapor deposition epitaxial diamond samples doped with various concentrations of boron. It was found that the experimentally detected boron activation energy in the samples decreased from 314 meV down to 101 meV with an increase of B/C ratio from 600 to 18000 ppm in the gas reactants. For the heavily doped samples, a transition from thermally activated valence band conduction to hopping within the impurity band (with apparent activation energy 20 meV) was detected at temperatures 120 150 K. Numerical simulation was used to estimate the impurity DOS broadening. Accurate determination of continuously altering activation energy, which takes place during the transformation of conduction mechanisms, was proposed by numerical differentiation of the Arrhenius plot. With increase of boron doping level the gradual decreasing of capture cross section from 3 x 10 13 down to 2 x 10 17 cm2 was noticed.
author_names: Vasily Zubkov

O V Kucherova

Sergey A Bogdanov

Anna V Zubkova

James E Butler

Vladimir A Ilyin

Andrey V Afanas'ev

Anatoly Leontievich Vikharev
title: Temperature admittance spectroscopy of boron doped chemical vapor deposition diamond
year: 2015

abstract: Evaluating interfering capacitance steps in admittance spectroscopy for solar cell defect analysis is still a problem which needs to be solved. While the common analysis developed by Walter et al.[1] is capable of extracting defect distributions from the capacitance data, it results in erroneous defect densities in the presence of overlapping capacitance steps. We derive an expression for the capacitance step caused by defects with a density of states distributed in energy. By adding several of these defect distributions, interfering capacitance steps can be described. Thus, it is possible to fit the entire capacitance spectrum simultaneously for all temperatures. We apply the presented method to Cu2ZnSnSe4 based solar cells with power conversion efficiencies between 5% and 7% Comparing the obtained defect parameters with the ones obtained by the method from Walter et al. reveals that the Walter method overestimates the defect densities in the case of overlapping capacitance steps.
author_names: Thomas Paul Weiss

Alex Redinger

David Regesch

Marina Mousel

Susanne Siebentritt
title: Direct Evaluation of Defect Distributions From Admittance Spectroscopy
venue: IEEE Journal of Photovoltaics
year: 2014

abstract: Admittance spectra and drive level capacitance profiles of several high performance Cu2ZnSn(Se,S)4 (CZTSSe) solar cells with bandgap ~1.0 1.5 eV are reported. In contrast to the case for Cu(In,Ga)(S,Se)2, the CZTSSe capacitance spectra exhibit a dielectric freeze out to the geometric capacitance plateau at moderately low frequencies and intermediate temperatures (120 200 K) These spectra reveal important information regarding the bulk properties of the CZTSSe films, such as the dielectric constant and a dominant acceptor with energy level of 0.13 0.2 eV depending on the bandgap. This deep acceptor leads to a carrier freeze out effect that quenches the CZTSSe fill factor and efficiency at low temperatures.
author_names: Oki Gunawan

Tayfun Gokmen

Charles W Warren

J David Cohen

Teodor K Todorov

D Aaron R Barkhouse

Santanu Bag

Jiang Tang

Byungha Shin

David B Mitzi
title: Electronic properties of the Cu2ZnSn(Se,S)4 absorber layer in solar cells as revealed by admittance spectroscopy and related methods
year: 2012

abstract: The effect of the electrostatic interaction of charges in multiple quantum wells of a doped heterostructure is studied by admittance spectroscopy methods and numerical self consistent calculations. Samples containing three InGaAs/GaAs quantum wells each 7 nm thick, separated by 150 nm barriers, are studied in detail. The InAs content in the wells is 22, 16, and 11.5% Experimentally and by simulation, it is shown that the effect of the relative carrier depletion in the middle quantum well occurs due to the joining of local spacecharge regions around the quantum wells and is accompanied by raise of the middle well potential. The quantitative characteristics of this effect are analyzed depending on temperature, barrier thickness, and dopant concentration.
author_names: Vasily Zubkov

Ilya N Yakovlev

Vladimir G Litvinov

A V Ermachihin

O V Kucherova

V N Cherkasova
title: Analysis of the electrostatic interaction of charges in multiple InGaAs/GaAs quantum wells by admittance spectroscopy methods
year: 2014