Evidences of the defect pool model in the dark current-voltage characteristics of hydrogenated amorphous silicon based p-i-n devices

Sturiale, A.; Rubinelli, Francisco Alberto

doi:10.1016/j.tsf.2008.04.002

Cited by 5 publications

(6 citation statements)

References 22 publications

(47 reference statements)

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“…3,15,21 As a consequence, the recombination rate is expected to exhibit a peak close to the p/i interface, which is confirmed by our simulations. Kroon and Van Table I (using E l ¼ 1.69 eV).…”

Section: Discussionsupporting

confidence: 85%

“…However, these values were adjusted by Sturiale and Rubinelli after analysis of the same data using D-AMPS. 15 Their study indicated that the mobility gaps of the studied materials were actually 0.08 eV smaller, implying a mobility gap of 1.72 eV for material deposited using no hydrogen dilution. This value resembles the values of 1.70 eV and 1.73 eV mentioned before and is also fairly close to the value we determined in this study by considering the activation energy curve.…”

Section: Simulationsmentioning

confidence: 93%

“…3, 15 We also tested it with another simulation package, D-AMPS, which was developed at INTEC, UNL (Universidad Nacional del Litoral) in Argentina. With this package too we were able to reproduce the curves only by applying the defect-pool model.…”

Section: Simulationsmentioning

confidence: 99%

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Thermal ideality factor of hydrogenated amorphous silicon p-i-n solar cells

Kind

Swaaij

Rubinelli

et al. 2011

Journal of Applied Physics

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The performance of hydrogenated amorphous silicon (a-Si:H) p-i-n solar cells is limited, as they contain a relatively high concentration of defects. The dark current voltage (JV) characteristics at low forward voltages of these devices are dominated by recombination processes. The recombination rate depends on the concentration of active recombination centers and the recombination efficacy of each of these centers. The first factor causes the ideality factor of the devices to be non-integer and to vary with voltage. The temperature dependence of the dark current can be expressed by its activation energy. For microcrystalline silicon solar cells the activation energy varies with voltage with a so-called thermal ideality factor of 2. This value was derived for devices with a spatially uniform defect distribution and reflects the recombination efficacy. Here we present results of a thickness series of a-Si:H p-i-n solar cells. We have matched the experimental curves with computer simulations, and show that the voltage-dependent ideality factor curve can be used to extract information on the cross sections for electron and hole capture. Also, the activation energy is used as a measure for the mobility gap, resulting in a mobility gap for a-Si:H of 1.69 eV. We find a thermal ideality factor close to 2 for all samples. This is explained with a theoretical derivation, followed by a comparison between the internal electric field strength and the spatial variation of the defect density in the intrinsic layer. The thermal ideality factor is shown to be insensitive to the defect distribution and the recombination profile in the device. It is, therefore, an appropriate parameter to characterize a-Si:H p-i-n devices, providing direct insight on the recombination efficacy.

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Section: Discussionsupporting

confidence: 85%

Section: Simulationsmentioning

confidence: 93%

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Thermal ideality factor of hydrogenated amorphous silicon p-i-n solar cells

Kind

Swaaij

Rubinelli

et al. 2011

Journal of Applied Physics

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“…This issue was not covered in our previous contribution due to its inherent complexity and an excessive extension of our manuscript. Although fittings of characteristics J – V and spectral responses (SR) of a‐S:H devices can be achieved with either the DPM or the UDM, the DPM is widely used in a‐S:H devices because it can successfully capture experimentally trends while the UDM could give rise to predictions in contradiction with some experimental findings .…”

Section: Introductionmentioning

confidence: 99%

Evaluation of the characteristic curves of a-Si:H based devices with the Simmons-Taylor approximation when the defect pool model is used

Greef

Rubinelli

2014

Phys. Status Solidi B

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The performance of a-Si:H devices is highly sensitive to the density of gap states: tail states are distributed in two exponentials and defect states are generated by dangling bonds (DB). The density of DB in a-Si:H can be evaluated with the defect pool model (DPM). Charge trapping and recombination of electron-hole pairs through tail states are described by the Shockley-Read-Hall (SRH) formalism while defect states behave as amphoteric. Equations derived with the SRH formalism can be simplified with the Simmons-Taylor's approximation (STA), especially with the "0 K" approximation (0KSTA). Amphoteric-like defect states were approximated by donor-and acceptor-like decoupled states (DSA). The accuracy of STA was tested in a-Si:H based devices when the density of DB is evaluated with the DPM for different illumination conditions, voltages, temperatures, and some key electrical parameters. Our code was modified to include both the STA and the DSA. Our results indicate that the STA is very accurate under illuminated conditions. Under dark conditions, the STA is acceptable for forward voltages but overestimates the dark current at reverse voltages. The 0KSTA can be used under illuminated conditions for any applied voltage and under dark conditions for forward voltages.

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“…This is to a large extent due to the higher defect density near the p-i and i-n interfaces than in the center of the intrinsic region, as predicted by the defect-pool model [4,5]. In addition to the distribution of recombination centers, the recombination efficacy also influences the recombination rate.…”

Section: Introductionmentioning

confidence: 99%