Camera‐based high frequency heterodyne lock‐in carrierographic (frequency‐domain photoluminescence) imaging of crystalline silicon wafers

Sun, Qiming; Melnikov, Alexander; Mandelis, Andreas

doi:10.1002/pssa.201532033

Cited by 23 publications

(16 citation statements)

References 34 publications

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“…Therefore, the value of γ can be used to physically interpret the linear or nonlinear behavior of a charge carrier recombination process with respect to the laser excitation and reveals the underlying radiative recombination process. It is an important parameter for the LIC process because nonlinear PL responses to the laser excitation, acting as a nonlinear frequency mixer, are essential for PL-based heterodyne LIC imaging. ,,, …”

Section: Theoretical Methodsmentioning

confidence: 99%

“…It is an important parameter for the LIC process because nonlinear PL responses to the laser excitation, acting as a nonlinear frequency mixer, are essential for PL-based heterodyne LIC imaging. 40,42,43,46 As opposed to CQD thin films, excitons in polycrystalline and amorphous Si wafers, upon their formation, immediately dissociate into free electrons and holes, with the dominant recombination process being via defect states. In this situation, the nonlinear recombination term an 2 in the rate equation…”

Section: Can Be Expressed Bymentioning

confidence: 99%

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Quantitative Analysis of Trap-State-Mediated Exciton Transport in Perovskite-Shelled PbS Quantum Dot Thin Films Using Photocarrier Diffusion-Wave Nondestructive Evaluation and Imaging

Yang

Mandelis

et al. 2016

J. Phys. Chem. C

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Perovskite-shelled colloidal quantum dots (CQDs) with low trap-state density are promising candidates for largescale, low-cost, and lightweight solar cell applications. However, even minimal trap states can significantly limit CQD-based solar cell efficiency. We reported trap-state-mediated exciton transports in methylammonium lead triiodide (MAPbI 3 ) perovskitepassivated PbS CQD thin films. Excitation power-dependent photocarrier radiometry (PCR) intensity study demonstrated the free (electrons/holes)-to-bound (acceptors/donors) and trap-state-related transition-induced nonlinear response of CQD thin films to excitation. The existence of shallow trap states (activation energy: 33.8−40.7 meV) was characterized using photothermal emission spectra at different modulation frequencies. CQD thin films were imaged, for the first time, by InGaAs-camera-based nondestructive homodyne and heterodyne lock-in carrierographies (LIC; spectrally gated dynamic photoluminescence imaging), clearly showcasing photocarrier density diffusion-wave inhomogeneities that stem from defect-associated multiple effective exciton lifetimes. PCR frequency scans, coupled with the trap-state-mediated exciton transport model, extracted multiple material and carrier transport parameters such as effective exciton lifetime τ E , hopping diffusivity D h , dark and bright state separation energy ΔE, and carrier trapping rate N T . Camera-based contactless homodyne and heterodyne LIC imaging of QD thin films was found to be a promising nondestructive characterization technique for monitoring optoelectronic qualities of QD materials and devices.

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Section: Theoretical Methodsmentioning

confidence: 99%

Section: Can Be Expressed Bymentioning

confidence: 99%

Quantitative Analysis of Trap-State-Mediated Exciton Transport in Perovskite-Shelled PbS Quantum Dot Thin Films Using Photocarrier Diffusion-Wave Nondestructive Evaluation and Imaging

Yang

Mandelis

et al. 2016

J. Phys. Chem. C

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“…Beyond that, the automated micro-cracks detection methods based on machine vision have been widely used in industry because of its convenience and efficiency (Sun et al, 2016;Teo and Abdullah, 2016;Tsai et al, 2015). The performance of these methods heavily relies on the features being used.…”

Section: Introductionmentioning

confidence: 99%

Micro-cracks detection of multicrystalline solar cell surface based on self-learning features and low-rank matrix recovery

Qian

Zhang

Cui

et al. 2018

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Purpose This paper aims to improve the generalization capability of feature extraction scheme by introducing a micro-cracks detection method based on self-learning features. Micro-cracks detection of multicrystalline solar cell surface based on machine vision is fast, economical, intelligent and easier for on-line detection. However, the generalization capability of feature extraction scheme adopted by existed methods is limited, which has become an obstacle for further improving the detection accuracy. Design/methodology/approach A novel micro-cracks detection method based on self-learning features and low-rank matrix recovery is proposed in this paper. First, the input image is preprocessed to suppress the noises and remove the busbars and fingers. Second, a self-learning feature extraction scheme in which the feature extraction templates are changed along with the input image is introduced. Third, the low-rank matrix recovery is applied to the decomposition of self-learning feature matrix for obtaining the preliminary detection result. Fourth, the preliminary detection result is optimized by incorporating the superpixel segmentation. Finally, the optimized result is further fine-tuned by morphological postprocessing. Findings Comprehensive evaluations are implemented on a data set which includes 120 testing images and corresponding human-annotated ground truth. Specifically, subjective evaluations show that the shape of detected micro-cracks is similar to the ground truth, and objective evaluations demonstrate that the proposed method has a high detection accuracy. Originality/value First, a self-learning feature extraction method which has good generalization capability is proposed. Second, the low-rank matrix recovery is combined with superpixel segmentation for locating the defective regions.

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“…Apart from these, measurements based on modulated excitation‐based techniques such as modulated photoluminescence (MPL) have been widely used after the work of Bruggemann et al, Trupke et al, and Giesecke et al With acexcitation, the advantage is that lock‐in amplifier based instrumentation can be used to separate the inphase and quadrature components as well as enhance the sensitivity of detecting weak luminescence. Sun et al incorporated ac lock‐in technique in luminescence imaging to enhance the sensitivity of these measurements. Both optical and electrical excitations are currently in use for solar cell‐related luminescence work.…”

Section: Introductionmentioning

confidence: 99%

Measurement of Relaxation Time of Excess Carriers in Si and CIGS Solar Cells by Modulated Electroluminescence Technique

Khatavkar

Muniappan

Kannan³

et al. 2017

Physica Status Solidi (a)

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Excess carrier lifetime plays a crucial role in determining the efficiency of solar cells. In this paper, we use the frequency dependence of inphase and quadrature components of modulated electroluminescence (MEL) to measure the relaxation time (decay) of excess carriers. The advantage of the MEL technique is that the relaxation time is obtained directly from the angular frequency at which the quadrature component peaks. It does not need knowledge of the material parameters like mobility, etc., and can be used for any finished solar cells which have detectable light emission. The experiment is easy to perform with standard electrical equipment. For silicon solar cells, the relaxation time is dominated by recombination and hence, the relaxation time is indeed the excess carrier lifetime. In contrast, for the CIGS solar cells investigated here, the relaxation time is dominated by trapping and emission from shallow minority carrier traps.

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Camera‐based high frequency heterodyne lock‐in carrierographic (frequency‐domain photoluminescence) imaging of crystalline silicon wafers

Cited by 23 publications

References 34 publications

Quantitative Analysis of Trap-State-Mediated Exciton Transport in Perovskite-Shelled PbS Quantum Dot Thin Films Using Photocarrier Diffusion-Wave Nondestructive Evaluation and Imaging

Quantitative Analysis of Trap-State-Mediated Exciton Transport in Perovskite-Shelled PbS Quantum Dot Thin Films Using Photocarrier Diffusion-Wave Nondestructive Evaluation and Imaging

Micro-cracks detection of multicrystalline solar cell surface based on self-learning features and low-rank matrix recovery

Measurement of Relaxation Time of Excess Carriers in Si and CIGS Solar Cells by Modulated Electroluminescence Technique

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