Towards the improvement of the stability of a-Si:H pin devices

Martins, Rodrigo; Águas, Hugo; Ferreira, I.; Fortunato, Elvira; Guimarães, L.

doi:10.1016/s0038-092x(01)00063-9

Cited by 5 publications

(8 citation statements)

References 8 publications

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“…Figures 2 and 3 show the calculated J -V characteristic and the spectral response, SR (external quantum efficiency), of the proposed cell structure. The obtained output photoparameters, J sc = 14.18 mA cm −2 , V oc = 0.82 V, FF = 0.58 and η = 6.75%, are close to the ones measured generally in conventional single a-Si:H p-i-n solar cells [1,19,20]. The external quantum efficiency is 0.73 at 0.4 μm and reaches a maximum value, about 0.85, between 0.52 and 0.56 μm; afterwards, it decreases strongly at long wavelengths.…”

Section: Resultssupporting

confidence: 81%

Computer simulation of the a-Si:H p–i–n solar cell performance sensitivity to the free carrier’s mobilities, the capture cross sections and the density of gap states

Meftah¹,

Belghachi²

2006

J. Phys.: Condens. Matter

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This paper deals with the effects of some material properties on the J -V characteristic of hydrogenated amorphous silicon (a-Si:H)-based p-i-n solar cell. The factors considered are the free carrier's mobilities, the capture cross sections of the gap states and the bulk density of states (i-layer DOS). Accurate investigation of the cell photo-parameters' sensitivity to these factors is carried out using a simulation program, previously developed by our group. The model is based on a complete set of Poisson and carrier continuity equations taking into account the defect pool model for the a-Si:H gap density of states. Ours results reveal the important role of the hole mobility when it takes low values, as given frequently in the literature, on the recombination rate at interface regions as well as in the bulk. This considerably affects the short-circuit current density (J sc ), the open-circuit voltage (V oc ), the fill factor (FF) and the conversion efficiency (η). Moreover, by changing separately the capture cross sections of the band's tails and those of dangling bonds we found more precisely that J sc , V oc , and η are more sensitive to the interface recombination while the FF seems to depend more on the bulk recombination. Ultimately, when the i-layer DOS is higher than 10 16 cm −3 , the recombination rate, which was first limited by the valence band tail's states, becomes limited by the dangling bond's states. Then, any further increase significantly deteriorates the solar cell performance.

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Section: Resultssupporting

confidence: 81%

Computer simulation of the a-Si:H p–i–n solar cell performance sensitivity to the free carrier’s mobilities, the capture cross sections and the density of gap states

Meftah¹,

Belghachi²

2006

J. Phys.: Condens. Matter

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“…However, an effective barrier can be made by the carrier accumulation at defect sites, which forces the increase in V oc of the p - i - n device, again leading to saturation. − The V oc value of device #2 with normal p-i-n layers showed quick degradation and a subsequent quick recovery, which indicated that the defect sites in the p , n -a-Si:H initial layers induced degradation; however, ultimately, the carriers were captured and accumulated at the defect sites. This accumulation is helpful in the recovery and saturation of V oc . − However, these data and this explanation based on only the initial state of light-induced degradation over approximately 10 h are pure speculation and are inadequate. More detailed study and analysis are needed for at least 1000 h, to give information such as the defect density, light intensity change, and temperature dependence.…”

Section: Resultsmentioning

confidence: 99%

“…The stability of J sc , V oc , FF, and PCE over 10 h of selected devices with such as p-i-n layers, T-MoO 3 (20 nm), and S-MoO 3 (7.5 nm) are also shown in Figure g–i, respectively. This could be ascribed to the higher importance of the interface between p and i layers than that between the i and n layers and the recombination of carriers reducing R sh and increasing R s , leading to poor FF values. − In the device with normal p-i-n layers, the doping elements in the doping layers can act as defect sites and thus are easily degraded under illumination. − This effect induces p , n -layer degradation and finally degradation of V oc because the residual boron doping or boron diffusion at the interface reduces the electrical field. − …”

Section: Resultsmentioning

confidence: 99%

“…In comparison, the V oc values obtained for the dopant-free structures containing MoO 3 were stable with increasing operation duration owing to the lower number of defect sites because of the absence of dopants, leading to a less contaminated oxide surface that was compacted and smooth, resulting in an increase in the electron lifetime and thus giving improved light stability. − …”

Section: Resultsmentioning

confidence: 99%

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Dopant-Free Hydrogenated Amorphous Silicon Thin-Film Solar Cells Using Molybdenum Oxide and Lithium Fluoride

et al. 2013

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Toxic doping gases are usually used to produce hydrogenated amorphous silicon (a-Si:H) layers in thin-film solar cells (TFSCs). Hence, an alternative structure that avoids the use of toxic gases is desirable. In this work, we replaced both the p-type-a-Si:H and n-type-a-Si:H layers simultaneously in a normal TFSC to form a structure that is dopant-free. Molybdenum oxide (MoO3) and lithium fluoride were used as the p-type and n-type layers, respectively. The effects of the deposition method and the thickness of the MoO3 layer on the device performance were investigated. The power-conversion efficiency of the optimized hybrid solar cell reached a maximum of 7.08%, which is remarkable considering the novel structure of the dopant-free devices. The light stability of the devices with and without MoO3 was also compared: the light stability of the device with MoO3 was found to be much better than that of the device without MoO3 and with p-i-n Si layers. This was ascribed to the insignificant number of defect sites generated by the nondoping elements, which led to a less contaminated, more compact, and smoother oxide surface, resulting in an increase in the electron lifetime and improved light stability. This work opens up a new direction toward the development of a truly dopant-free device that does not involve the use of toxic gases during fabrication and provides the potential for further enhancement of the efficiency of future dopant-free solar cells.

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“…Eliminating this effect allows the development of a-Si:H solar cells with higher stabilized efficiency. Several a-Si:H-based solar cell (single or multijunctions) structures with higher resistance to the light soaking effect and higher conversion efficiency has been developed by using new materials and techniques [7][8][9][10][11][12][13][14].…”

Section: Introductionmentioning

confidence: 99%

Two-dimensional modelling and simulation of hydrogenated amorphous silicon p+–n–n+ solar cell

Letha

Hwang

2009

Journal of Non-Crystalline Solids

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Towards the improvement of the stability of a-Si:H pin devices

Cited by 5 publications

References 8 publications

Computer simulation of the a-Si:H p–i–n solar cell performance sensitivity to the free carrier’s mobilities, the capture cross sections and the density of gap states

Computer simulation of the a-Si:H p–i–n solar cell performance sensitivity to the free carrier’s mobilities, the capture cross sections and the density of gap states

Dopant-Free Hydrogenated Amorphous Silicon Thin-Film Solar Cells Using Molybdenum Oxide and Lithium Fluoride

Two-dimensional modelling and simulation of hydrogenated amorphous silicon p+–n–n+ solar cell

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