Characterization of the SnO/sub 2//p and ZnO/p contact resistance and junction properties in a-Si p-i-n solar cells and modules

Hegedus, Steven; Kaplan, R.; Ganguly, Gautam; Wood, G.

doi:10.1109/pvsc.2000.915977

Cited by 3 publications

(3 citation statements)

References 6 publications

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“…The ZnO/p contact gave lower V OC and FF, which was widely attributed to a barrier or contact resistance. 42 R was determined as in plot (c) for cells with different path length in the ZnO or SnO 2 and the contact resistance was determined by extrapolating to zero path-length. This analysis showed that the ZnO/p contact was ohmic with low resistance, contrary to standard assumptions.…”

Section: Parasitic Effectsmentioning

confidence: 99%

Thin‐film solar cells: device measurements and analysis

Hegedus

Shafarman

2004

Progress in Photovoltaics

1,029

740

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Characterization of amorphous Si, CdTe, and Cu(InGa)Se 2 -based thin-film solar cells is described with focus on the deviations in device behavior from standard device models. Quantum efficiency (QE), current-voltage (J-V), and admittance measurements are reviewed with regard to aspects of interpretation unique to the thin-film solar cells. In each case, methods are presented for characterizing parasitic effects common in these solar cells in order to identify loss mechanisms and reveal fundamental device properties. Differences between these thin-film solar cells and idealized devices are largely due to a high density of defect states in the absorbing layers and to parasitic losses due to the device structure and contacts. There is also commonly a voltage-dependent photocurrent collection which affects J-V and QE measurements. The voltage and light bias dependence of these measurements can be used to diagnose specific losses. Examples of how these losses impact the QE, J-V, and admittance characterization are shown for each type of solar cell.Solar cell operation, either crystalline or thin film, can be described by identifying loss mechanisms. These can be divided into three categories. First are recombination losses which limit the open-circuit voltage V OC . Second are parasitic losses, such as series resistance, shunt conductance, and voltage-dependent current collection, which primarily impact the fill factor (FF), but can also reduce short circuit current J SC and V OC . Finally, there are optical losses which limit generation of carriers and, therefore, J SC . We focus on losses largely unique to TFSCs.Physical and electrical properties of TFSCs which cause them to have different losses from the standard 'textbook' crystalline Si (c-Si) cells include: * TFSC absorber layers have much higher absorption coefficients than c-Si so a large fraction of the photogeneration occurs near the interface and in the high field space charge region (SCR). This enables high currents, even with relatively small collection lengths; * the semiconductor films often have a range of shallow and deep defect levels or defect bands within the bandgap. These result from imperfect crystallinity or amorphous structure and from the use of low-cost materials and processes optimized for high throughput and low cost as much as for high device efficiency. This can create different recombination mechanisms than radiative band-to-band recombination commonly found in ideal crystalline semiconductor devices; * poor minority carrier lifetime, due to the above factors, leads to increased reliance on the electric field for sufficient minority carrier collection rather than diffusion alone. This often results in voltage-dependent collection of light-generated current; * TFSCs are heterojunction device structures with high densities of defect states at interfaces which can provide a path for interface recombination; * the grain boundaries in polycrystalline Cu(InGa)Se 2 and CdTe devices may act as high recombination surfaces or shunt paths. This l...

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Section: Parasitic Effectsmentioning

confidence: 99%

Thin‐film solar cells: device measurements and analysis

Hegedus

Shafarman

2004

Progress in Photovoltaics

1,029

740

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“…Transparent conductive oxide (TCO) film which forms the front contact of the a-Si:H cell, can also introduce rough interfaces in cell if textured. Optimum texturing with best optical and electrical properties for TCO materials is desired [10]. Aluminum doped zinc oxide (AZO), tin oxide (SnO), indium tin oxide (ITO), are some of the well known TCO materials.…”

Section: Development Of Tco Filmsmentioning

confidence: 99%

Development, characterization and interface engineering of films for enhanced amorphous silicon solar cell performance

Joshi¹,

Steen²,

Sivakumar³

et al. 2010

2010 35th IEEE Photovoltaic Specialists Conference

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We are reporting comprehensive efforts for development and characterization of thin film PECVD a:SiH and TCO materials, and novel surface modification techniques to enhance solar cell performance. All process development and cell fabrication was conducted on 200 mm substrate wafers on CMOS manufacturing platform tools. Entire process parameter space of our PECVD tool was explored to enable increased understanding for process parameter effects on phase transition between amorphous and micro-crystalline Si films as well as film quality. In-depth characterizations helped understood material properties. It was observed that a range of crystallinity can be achieved by carefully tuning the plasma conditions. A PVD process for in-situ highly textured TCO surface with high overall transmittance was developed. Novel modification techniques were designed, which significantly improved open circuit voltage (Voc) and current density (Jsc). Highest Voc and Jsc achieved till date is 920 mV and 15mA/cm 2 on 0.16cm 2 devices. Initial efficiency of 8.4 % is also reported on a 0.16cm 2 single junction device.

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“…The main research activities in the photovoltaic field are related to materials development, which can be obtained at relatively low cost and to improve the conversion efficiency [4][5][6][7]. Owing to its many exciting technological applications, hydrogenated amorphous silicon, a-Si:H, became the most intensively studied amorphous semiconductor [8,9].…”

Section: Introductionmentioning

confidence: 99%