Relationship between absorber layer defect density and performance of a‐Si:H and µc‐Si:H solar cells studied over a wide range of defect densities generated by 2MeV electron bombardment

Theoretically predicted values of the open circuit voltage (VOC) for a-Si:H or μc-Si:H based solar cells are substantially higher than the values achieved in of state-of-the-art devices. Fundamentally, open circuit voltage is determined by generation-recombination kinetics, where recombination is often controlled by the defect density in the absorber layer of a solar cell. The latter aspect is the focus of the paper. The relation between the VOC and the bulk recombination in the absorber layer is addressed in experiment by varying the defect density. The absorber layer defect density (spin density, NS, monitored with ESR) in a-Si:H and μc-Si:H solar cells was varied over two orders of magnitude using a 2 MeV electron bombardment and successive stepwise annealing. The results of the electron bombardment experiment are analyzed with respect to the illumination intensity dependency of the VOC, measured for the same set of a-Si:H and μc-Si:H solar cells. We find that the VOC of a-Si:H solar cells is not limited by defects in the bulk of the absorber layer, even at relatively high defect density up to 3–5 × 1016 cm−3 and, therefore, other limiting mechanisms have to be identified to improve voltage in these devices. In contrast, μc-Si:H solar cells show nearly classical VOC–NS relation. The bulk defect density in μc-Si:H absorber layer is thus likely the key limiting factor for VOC in these devices at present status of material quality (NS of 3–7 × 1015 cm−3). Further optimization of μc-Si:H in terms of bulk defect density is highly relevant for VOC improvement in solar cells.

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Efficiency enhancement of CZTSSe solar cells via screening the absorber layer by examining of different possible defects

Scientific Reports ◽

10.1038/s41598-020-75686-2 ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

Mehran Minbashi ◽

Arash Ghobadi ◽

Elnaz Yazdani ◽

Amirhossein Ahmadkhan Kordbacheh ◽

Ali Hajjiah

Keyword(s):

Solar Cells ◽

Solar Cell ◽

Valence Band Maximum ◽

Absorber Layer ◽

Cell Performance ◽

Secondary Phases ◽

Cell Efficiency ◽

Wide Range ◽

Low Efficiency ◽

Defect Densities

AbstractThis study represents the investigation of earth-abundant and non-toxic CZTSSe absorber materials in kesterite solar cell by using the Finite Element Method (FEM) with (1) electrical, and (2) optical approaches. The simulated results have been validated with the experimental results to define guidelines for boosting the cell performance. For improving the cell efficiency, potential barrier variations in the front contact, and the effect of different lattice defects in the CZTSSe absorber layer have been examined. Controlling the defects and the secondary phases of absorber layer have significant influence on the cell performance improvement. Previous studies have demonstrated that, synthesis of CZTSSe:Na nanocrystals and controlling the S/(S + Se), Cu/(Zn + Sn), and Zn/Sn ratios (stoichiometry) have significant effects on the reduction of trap-assisted recombination (Shockley–Read–Hall recombination model). In this work, a screening-based approach has been employed to study the cell efficiency over a wide range of defect densities. Two categorized defect types including benign defects ($${N}_{t}<{10}^{16}$$ N t < 10 16 cm−3 , Nt defines trap density) and harmful defects $${(N}_{t}>{10}^{16}$$ ( N t > 10 16 cm−3) in the absorber bandgap in the CZTSSe solar cell, by analyzing their position changes with respect to the electron Fermi level (Efn) and the Valence Band Maximum positions have been identified. It is realized that, the harmful defects are the dominant reason for the low efficiency of the kesterite solar cells, therefore, reducing the number of harmful defects and also total defect densities lead to the power conversion efficiency record of 19.06%. This increment makes the CZTSSe solar cells as a promising candidate for industrial and commercial applications.

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Investigation on the Relative Influence of Absorber Layer Defect States Over Performance of Pb-Based and Sn-Based Perovskite Solar Cells

Renewable Energy and Climate Change - Smart Innovation, Systems and Technologies ◽

10.1007/978-981-32-9578-0_10 ◽

2019 ◽

pp. 109-118

Author(s):

Piyush Baldha ◽

Krunal Patel ◽

Kshitij Bhargava

Keyword(s):

Solar Cells ◽

Perovskite Solar Cells ◽

Absorber Layer ◽

Relative Influence ◽

Defect States ◽

Layer Defect

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Computational Study of Inverted All-Inorganic Perovskite Solar Cells Based on CsPbIxBr3-X Absorber Layer with Band Gap of 1.78 eV

10.26434/chemrxiv.13382069.v1 ◽

2020 ◽

Author(s):

Nahuel Martínez ◽

Carlos Pinzón ◽

Guillermo Casas ◽

Fernando Alvira ◽

Marcelo Cappelletti

Keyword(s):

Solar Cells ◽

Band Gap ◽

High Efficiency ◽

Defect Density ◽

Computational Study ◽

Perovskite Solar Cells ◽

Absorber Layer ◽

Inorganic Materials ◽

Tandem Solar Cells ◽

Inorganic Perovskite

All-inorganic perovskite solar cells (PSCs) with inverted p-i-n configuration have not yet reached the high efficiency achieved in the normal n-i-p architecture. However, the inverted all-inorganic PSC are more compatible with the fabrication of tandem solar cells. In this work, a theoretical study of all-inorganic PSCs with inverted structure ITO/HTL/CsPbIxBr3−x/ETL/Ag, has been performed by means of computer simulation. Four p‐type inorganic materials (NiO, Cu2O, CuSCN and CuI) and three n-type inorganic materials (ZnO, TiO2 and SnO2) were used as hole and electron transport layers (HTL and ETL), respectively. A band gap of 1.78 eV was used for the CsPbI x Br3−x perovskite layer. The simulation results allow identifying that CuI and ZnO are the most appropriate materials as HTL and ETL, respectively. Additionally, optimized values of thickness, acceptor density and defect density in the absorber layer have been obtained for the ITO/CuI/CsPbI x Br3−x /ZnO/Ag, from which, an optimum efficiency of 21.82% was achieved. These promising theoretical results aim to improve the manufacturing process of inverted all-inorganic PSCs and to enhance the performance of perovskite–perovskite tandem solar cells.

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Effect of C Impurities in a-Si:H as Measured by Drive-Level Capacitance, Photo Current, and Electron Spin Resonance

MRS Proceedings ◽

10.1557/proc-297-375 ◽

1993 ◽

Vol 297 ◽

Author(s):

J. Hautala ◽

T. Unold ◽

J.D. Cohen

Keyword(s):

Electron Spin Resonance ◽

Electron Spin ◽

Defect Density ◽

Drive Level ◽

Level Data ◽

Definite Effect ◽

Wide Range ◽

Spin Resonance ◽

Defect Densities ◽

Photo Current

The effect of C impurities in a-Si:H in levels of 0.4 to 2.6 at. % were studied over a wide range of metastable defect densities. Three complimentary experimental techniques [electron spin resonance (ESR), drive-level capacitance (DLC) and photo-current] were employed to track the material's defect density with light soaking and annealing, as well as Urbach energies, midgap absorption and mobility gaps energies as a function of the C content. Our results show C impurities have a definite effect on the initial and saturated defect densities, as well as the midgap absorption and Urbach energies at levels 1 at. % and above. The results indicate that C acts mainly as a center for increased disorder in the material which results in an increase in the bandtail widths, and consequently an increase in intrinsic defects. Comparison to the ESR and drive-level data show an excellent agreement between these two techniques in determining the bulk defect densities in a-Si:H.

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Defect generation and propagation in GaAs solar cells

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100106697 ◽

1988 ◽

Vol 46 ◽

pp. 926-927

Author(s):

K.M. Jones ◽

R.J. Matson ◽

M.M. Al-Jassim ◽

S.M. Vernon

Keyword(s):

Solar Cells ◽

Minority Carrier ◽

Lattice Mismatch ◽

Defect Density ◽

Wide Bandgap ◽

Cell Parameters ◽

P Concentration ◽

Gaas Substrates ◽

Wide Range ◽

Low Pressure Mocvd

It is well known that dislocations have deleterious effects on the performance of minority carrier semiconductor devices. In a previous study(1), the results of an EBIC examination of GaAsP wide bandgap solar cells was reported. The effects of defects in the 106-108 cm-2 range on various cell parameters were investigated. However, the equally important 104-106 range was not studied. In this work, we report a study on defects in low bandgap (1.4 eV) GaAs cells in the 104-108 cm-2 range. These cells were grown by low pressure MOCVD on GaAs substrates. In order to introduce dislocations with such a wide range of densities, an intermediate mismatched layer of GaAs1_xPx was introduced into the structure (Fig. 1). Five different device-type structures were grown in which the P concentration (x) was varied from 2% to 32%. These concentrations correspond to a lattice mismatch of 7.3x10-4 and 1.2xl0-2respectively. As expected, the higher the P concentration the larger the mismatch being introduced into the system and therefore, the higher the defect density.

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Metastability Under High-Intensity Light of Device-Quality He-Diluted, H2-Diluted and Standard a-Si:H Films Deposited Between 50°C and 350°C

MRS Proceedings ◽

10.1557/proc-336-281 ◽

1994 ◽

Vol 336 ◽

Cited By ~ 10

Author(s):

P. Morin ◽

P. Roca i Cabarrocas

Keyword(s):

High Intensity ◽

Defect Density ◽

Red Light ◽

Rf Power ◽

Wide Range ◽

Order Of Magnitude ◽

Kinetics Of ◽

Defect Densities ◽

High Intensity Light

ABSTRACTWe report the results of a study of the metastability under illumination by high intensity red light of device quality a-Si:H thin films deposited using a wide range of deposition conditions. The process variables included substrate temperature, pressure, rf power, and dilution of silane by He or H2. In-situ Monitoring of the sample conductivity and defect density during light-soaking provides the kinetics of the degradation of the electronic properties of the films. We observe equilibration of the photoconductivity and of the defect density. The characteristic time of equilibration τse of the defect density varies by more than an order of magnitude, dividing the samples into two groups: one group with a τse on the order of 103 seconds, the other with a τse on the order of 104 seconds. Low steady state defect densities combined with high ημτ products are observed for “standard” a-Si:H deposited between 100°C and 250°C and He-diluted films deposited above 250°C.

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Computational Probing of Tin-based Lead-free Perovskite Solar Cells: Effects of Absorber Parameters and Various ETL Materials on Device Performance

10.21203/rs.3.rs-658718/v1 ◽

2021 ◽

Author(s):

Arunkumar Prabhakaran Shyma ◽

Raja Sellappan

Keyword(s):

Solar Cells ◽

Defect Density ◽

Perovskite Solar Cells ◽

Lead Toxicity ◽

Open Circuit ◽

Absorber Layer ◽

Transport Layer ◽

Electron Transport Layer ◽

Maximum Efficiency ◽

Research Attention

Abstract Tin-based perovskite solar cells have gained global research attention due to the lead toxicity and health risk associated with its lead-based analogue. The promising opto-electrical properties of the Tin-based perovskite have attracted researchers to work on developing solar cells with higher efficiencies comparable to Lead-based analogues. Tin-based perovskites outperform the lead-based ones in areas like optimal band gap and carrier mobility. A detailed understanding regarding the effects of each parameters and working conditions on Tin-based perovskite is crucial in order to improve the efficiency. In the present work, we have carried out a numerical simulation of planar heterojunction Tin-based (CH3NH3SnI3) perovskite solar cell employing SCAPS 1D simulator. Device parameters namely thickness of the absorber layer, defect density of the absorber layer, working temperature, series resistance, metal work function have been exclusively investigated. ZnO has been employed as the ETL (Electron transport layer) material in the initial simulation to obtain optimized parameters and attained a maximum efficiency of 19.62 % with 1.1089 V open circuit potential (Voc) at 700 nm thickness (absorber layer). Further, different ETL materials have been introduced into the optimized device architecture and Zn2SnO4 based device delivers an efficiency of 24.3 % with a Voc of 1.1857 V. The obtained results indicate a strong possibility to model and construct better performing perovskite solar cells based on Tin (Sn) with Zn2SnO4 as ETL layer.

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