Understanding inversion layers and band discontinuities in hydrogenated amorphous silicon/crystalline silicon heterojunctions from the temperature dependence of the capacitance

Maslova, Olga; Brézard-Oudot, Aurore; Gueunier‐Farret, Marie‐Estelle; Alvarez, José; Favre, Wilfried; Muñoz, Delfina; Kleider, Jean‐Paul

doi:10.1063/1.4826920

Cited by 18 publications

(20 citation statements)

References 17 publications

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“…The small frequency dispersion of C-T curves at low temperatures has also been observed by other authors [24,25], and is related to hole response and collection at the p-side, but we will not go further into these details here. The overall capacitance increase with temperature is very similar to that previously observed on the high efficiency cell from INES [21].…”

Section: Temperature Dependencesupporting

confidence: 87%

“…8 One might argue that strong temperature dependence of physical parameters like the position of the Fermi level in a-Si:H or the valence band offset might be able to reconcile calculated and experimental data. This is not the case and we have shown that even with unreasonable temperature dependences of these parameters the calculated capacitance still exhibits weaker temperature dependence than observed experimentally [21]. This emphasizes the failure of the existing theory of the depletion capacitance that neglects minority carriers in the calculation of the space charge in cSi.…”

Section: Discussionmentioning

confidence: 42%

“…instead of increasing linearly as would be expected if V int would follow V d [26]. The same origin of the stronger temperature dependence and low intercept voltage value of 1/C 2 can be further evidenced if one considers the apparent diffusion voltage, V d app , obtained from capacitance data as defined in [21]:…”

Section: Discussionmentioning

confidence: 86%

“…Recently we have developed a complete analytical calculation of the a-Si:H/c-Si heterojunction capacitance [21]. We have solved Poisson's equation in both c-Si and a-Si:H, taking into account the overall charge neutrality from Eq.…”

Section: Calculation Of the A-si:h/c-si Heterojunction Capacitancementioning

confidence: 99%

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Revisiting the theory and usage of junction capacitance: Application to high efficiency amorphous/crystalline silicon heterojunction solar cells

Kleider

Alvarez

Brézard-Oudot

et al. 2015

Solar Energy Materials and Solar Cells

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International audienceWe briefly review the basic concepts of junction capacitance and the peculiarities related to amorphous semiconductors, paying tribute to Cohen and to his pioneering work. We extend the discussion to very high efficiency silicon heterojunction (SiHET) solar cells where both an amorphous semiconductor, namely hydrogenated amorphous silicon, and heterojunctions are present. By presenting both modeling and experimental results, we demonstrate that the conventional theory of junction capacitance based on the depletion approximation in the space charge region, cannot reproduce the capacitance data obtained on SiHET cells. The experimental temperature dependence is significantly stronger than that of the depletion-layer capacitance, while the bias dependence yields underestimated values of the diffusion potential, leading to strong errors if applied to the determination of band offsets using the procedure proposed precedingly in the literature. We demonstrate that this is not related to the amorphous nature of a-Si:H, but to the existence of a strongly inverted c-Si surface layer that requires minority carriers to be taken into account in the analysis of the junction capacitance

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Section: Temperature Dependencesupporting

confidence: 87%

Section: Discussionmentioning

confidence: 42%

Section: Discussionmentioning

confidence: 86%

Section: Calculation Of the A-si:h/c-si Heterojunction Capacitancementioning

confidence: 99%

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Revisiting the theory and usage of junction capacitance: Application to high efficiency amorphous/crystalline silicon heterojunction solar cells

Kleider

Alvarez

Brézard-Oudot

et al. 2015

Solar Energy Materials and Solar Cells

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“…2 In recent years, a-Si:H layers also garnered significant attention, thanks to their excellent crystalline silicon (c-Si) surface passivation properties, even when only a few nm thin. [3][4][5][6][7][8] This property is exploited with remarkable success for passivating-contact fabrication in silicon heterojunction (SHJ) solar cells, [9][10][11][12][13][14][15][16][17][18][19][20][21][22] with reported conversion cell efficiencies as high as 26.3%. 23 For any solar cell technology, an important criterion for ultimate device performance is its stability under prolonged light exposure.…”

mentioning

confidence: 99%

Light-induced performance increase of silicon heterojunction solar cells

Kobayashi

Wolf

Levrat

et al. 2016

Applied Physics Letters

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Silicon heterojunction solar cells consist of crystalline silicon (c-Si) wafers coated with doped/intrinsic hydrogenated amorphous silicon (a-Si:H) bilayers for passivating-contact formation. Here, we unambiguously demonstrate that carrier injection either due to light soaking or (dark) forward-voltage bias increases the open circuit voltage and fill factor of finished cells, leading to a conversion efficiency gain of up to 0.3% absolute. This phenomenon contrasts markedly with the light-induced degradation known for thin-film a-Si:H solar cells. We associate our performance gain with an increase in surface passivation, which we find is specific to doped a-Si:H/c-Si structures. Our experiments suggest that this improvement originates from a reduced density of recombination-active interface states. To understand the time dependence of the observed phenomena, a kinetic model is presented.

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Recent Progress in Understanding the Properties of the Amorphous Silicon/Crystalline Silicon Interface

Kleider

Alvarez

Brüggemann

et al. 2019

Physica Status Solidi (a)

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The authors review experimental and modeling approaches developed at GeePs to have a better knowledge and understanding of the interface between hydrogenated amorphous silicon (a‐Si:H) and crystalline silicon (c‐Si) in heterojunction solar cells. The authors emphasize the existence of a strong inversion layer at the c‐Si surface for both (n) a‐Si:H/(p) c‐Si and (p) a‐Si:H/(n) c‐Si heterojunctions. Conductive probe atomic force microscopy reveals the existence of a conductive channel at the c‐Si surface. The analysis of complementary lateral planar conductance and capacitance measurements allows for a better description of the band diagram in both types of heterojunctions especially through the determination of band offset values. Furthermore, the passivation properties of the (i) a‐Si:H buffer layer are studied by modeling the volume defects in a‐Si:H with the defect‐pool model. In particular, the DOS in the very thin (i) a‐Si:H layers is much larger than in bulk (i) a‐Si:H because the Fermi level position favors defect creation. Surface defects in c‐Si at the a‐Si:H/c‐Si interface are then quantified and the general trends of effective lifetime measurements with the (i) a‐Si:H layer thickness can be explained, notably the increase of the effective lifetime in c‐Si with increasing the (i) a‐Si:H buffer thickness.

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Understanding inversion layers and band discontinuities in hydrogenated amorphous silicon/crystalline silicon heterojunctions from the temperature dependence of the capacitance

Cited by 18 publications

References 17 publications

Revisiting the theory and usage of junction capacitance: Application to high efficiency amorphous/crystalline silicon heterojunction solar cells

Revisiting the theory and usage of junction capacitance: Application to high efficiency amorphous/crystalline silicon heterojunction solar cells

Light-induced performance increase of silicon heterojunction solar cells

Recent Progress in Understanding the Properties of the Amorphous Silicon/Crystalline Silicon Interface

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