Impact of different capping layers on carrier injection efficiency between amorphous and crystalline silicon measured using photoluminescence

Paduthol, Appu; Juhl, Mattias K.; Nogay, Gizem; Löper, P.; Ingenito, Andrea; Trupke, Thorsten

doi:10.1016/j.solmat.2018.07.016

Cited by 9 publications

(10 citation statements)

References 13 publications

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“…49 Meanwhile, Paduthol et al measured spectral responses of PL and compared them with IQEs calculated from absorption losses in a-Si:H to quantify such free-carrier couplings. 50,51 In this section, applying the same concept mentioned above, we also find direct evidence of the freecarrier coupling despite our very different approach compared to the previous works. Figure 4 shows typical PL spectra captured from c-Si samples capped with a-Si:H films.…”

Section: Acs Applied Energy Materialssupporting

confidence: 60%

“…Recently, several works have reported free-carrier coupling from a-Si:H passivation films with c-Si substrates in heterojunction solar cells. − Using internal quantum efficiency (IQE) and ellipsometry measurements, Holman et al found an electronic coupling of free carriers generated in a-Si:H films with c-Si absorbers, thus adding to the final photocurrent of their c-Si heterojunction cells . Meanwhile, Paduthol et al measured spectral responses of PL and compared them with IQEs calculated from absorption losses in a-Si:H to quantify such free-carrier couplings. , In this section, applying the same concept mentioned above, we also find direct evidence of the free-carrier coupling despite our very different approach compared to the previous works.…”

Section: Resultsmentioning

confidence: 99%

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Sub-Bandgap Luminescence from Doped Polycrystalline and Amorphous Silicon Films and Its Application to Understanding Passivating-Contact Solar Cells

Nguyen

Liu

Yan

et al. 2018

ACS Appl. Energy Mater.

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We report luminescence phenomena from doped polycrystalline silicon (poly-Si) films and their applications to study carrier transport properties in passivating-contact solar cells. Low-temperature luminescence spectra emitted from doped poly-Si layers are found to be very broad and stretched from the crystalline silicon (c-Si) luminescence peak to significantly lower energies. This suggests that these layers contain radiative defect levels whose energies are continuously distributed from the band edges to deep levels in the poly-Si bandgap. Moreover, photoinduced carriers inside poly-Si layers are found to be completely blocked by an ultrathin SiO x interlayer (∼1.3 nm). This demonstrates that there is no free-carrier coupling from poly-Si layers in practical passivating-contact solar cells. Finally, we demonstrate that the same principle can be applied to study carrier transport properties in hydrogenated amorphous silicon films.

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Section: Acs Applied Energy Materialssupporting

confidence: 60%

Section: Resultsmentioning

confidence: 99%

Sub-Bandgap Luminescence from Doped Polycrystalline and Amorphous Silicon Films and Its Application to Understanding Passivating-Contact Solar Cells

Nguyen

Liu

Yan

et al. 2018

ACS Appl. Energy Mater.

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“…This effect stems from the lower conductivity of doped a-Si:H compared to crystalline silicon, band offsets between these two phases [9] [10], and the formation of an opposing Schottky contact between a-Si:H and the transparent conductive oxide (TCO) [11]- [13]. In addition, the use of a-Si:H (bandgap of ~1.7 eV) on the light-incoming side of the device leads to severe short-wavelength (below 500 nm [1], [14]) parasitic light absorption, part light absorbed in the instrinsic a-Si:H ((i)a-Si:H) layers and all light absorbed in the doped a-Si:H layer being lost [14], [15]. This typically causes a short circuit current density (Jsc) loss of up to 2.1 mAcm -2 compared to the one of a cell with an ideal cell frontside [15].…”

Section: Introductionmentioning

confidence: 99%

23.5%-efficient silicon heterojunction silicon solar cell using molybdenum oxide as hole-selective contact

et al. 2020

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Interest in silicon heterojunction solar cells is growing due to their manufacturing simplicity and record efficiencies. A significant limitation of these devices stems from parasitic absorption in the amorphous silicon layers. This can be mitigated replacing the traditional (p) and (n) doped amorphous silicon selective layers by other materials. While promising results have been achieved using molybdenum oxide (MoOx) as front-side hole-selective layer, charge transport mechanisms in that contact stack have remained elusive and device efficiencies below predictions. By carefully analyzing the influence of the MoOx and intrinsic a-Si:H thicknesses on current-voltage properties, we discuss transport and performance-loss mechanisms. In particular, we find that thinning down the MoOx and (i) a-Si:H layers (down to 4 nm and 6 nm respectively) mitigates parasitic optical sub-bandgap MoOx absorption and drastically enhances charge transport, while still providing excellent passivation and selectivity. High-resolution transmission microscopy reveals that such thin MoOx layer remains continuous and close to a MoO3 stoichiometry in spite of the reactive sputtering and annealing steps involved in the electrode deposition. Based on these insights, a screen-printed device reaching a certified efficiency of 23.5% and a fill factor of 81.8% is demonstrated, bridging the gap with traditional Si-based contacts and demonstrating that dopant-free selective contacts can rival traditional approaches.

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“…This is a lower fraction than reported for a‐Si:H/c‐Si heterojunctions with the respective increase in J sc of only 0.05 mA cm −2 . [ 25 ]…”

Section: Resultsmentioning

confidence: 99%

“…It has previously been shown in literature for silicon heterojunction solar cells that carriers that are photo‐generated in the amorphous silicon can be efficiently electronically injected into the crystalline silicon, adding to the cell's photocurrent. [ 23–25 ] Here we analyze this effect and vary the poly‐Si thickness on the front, including ultra‐thin (down to 10 nm) values for the cells with POLO junctions. This effect would reduce the parasitic absorption in the poly‐Si as compared with the expectations based on ray‐tracing simulations.…”

Section: Introductionmentioning

confidence: 99%

Ultra‐Thin Poly‐Si Layers: Passivation Quality, Utilization of Charge Carriers Generated in the Poly‐Si and Application on Screen‐Printed Double‐Side Contacted Polycrystalline Si on Oxide Cells

et al. 2020

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Herein, the various measures to improve the efficiency of large‐area screen‐printed double‐side contacted polycrystalline Si on oxide (POLO)‐cells are experimentally demonstrated. The short‐circuit current density Jsc increases by 0.6 mA cm−2 upon reducing the thickness of poly‐Si from 25 to 10 nm due to the reduction of the parasitic absorption in the poly‐Si layer at the textured front side of the cell. Additionally, it is shown for the first time that the minority carriers generated by light absorbed in the poly‐Si layer can at least partially be transferred into the crystalline Si base. Remarkably high implied open‐circuit voltage Voc,impl values are achieved with n‐type cell precursors by introducing an hydrogenation step by AlxOy after reducing the poly‐Si thickness, and by an additional annealing step after sputtering of transparent conductive oxides (TCOs). All cell precursors show Voc,impl values of up to 740 mV independent of the poly‐Si thickness. A reduction in the open‐circuit voltage Voc is observed during back‐end processing to 728 mV as measured on the final cells. A certified cell energy conversion efficiency of 22.3% is reported.

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Impact of different capping layers on carrier injection efficiency between amorphous and crystalline silicon measured using photoluminescence

Cited by 9 publications

References 13 publications

Sub-Bandgap Luminescence from Doped Polycrystalline and Amorphous Silicon Films and Its Application to Understanding Passivating-Contact Solar Cells

Sub-Bandgap Luminescence from Doped Polycrystalline and Amorphous Silicon Films and Its Application to Understanding Passivating-Contact Solar Cells

23.5%-efficient silicon heterojunction silicon solar cell using molybdenum oxide as hole-selective contact

Ultra‐Thin Poly‐Si Layers: Passivation Quality, Utilization of Charge Carriers Generated in the Poly‐Si and Application on Screen‐Printed Double‐Side Contacted Polycrystalline Si on Oxide Cells

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