Interdigitated back contact solar cells with polycrystalline silicon on oxide passivating contacts for both polarities

Haase, Felix; Kiefer, Fabian; Schäfer, Sören; Kruse, Christian; Krügener, Jan; Brendel, Rolf; Peibst, Robby

doi:10.7567/jjap.56.08mb15

Cited by 78 publications

(47 citation statements)

References 17 publications

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“…Recently, different high efficiency silicon solar cells with passivating contacts have been reported . Aside from hydrogen‐rich amorphous (a‐) silicon/crystalline (c‐) silicon junction solar cells , polycrystalline (poly) silicon on interfacial oxide (POLO) junctions show an excellent passivation quality while featuring low contact resistances .…”

Section: Introductionmentioning

confidence: 99%

On the recombination behavior of p⁺-type polysilicon on oxide junctions deposited by different methods on textured and planar surfaces

Larionova

Turcu

Reiter

et al. 2017

Phys. Status Solidi A

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We investigate the passivation quality of hole‐collecting junctions consisting of thermally or wet‐chemically grown interfacial oxides, sandwiched between a monocrystalline‐Si substrate and a p‐type polycrystalline‐silicon (Si) layer. The three different approaches for polycrystalline‐Si preparation are compared: the plasma‐enhanced chemical vapor deposition (PECVD) of in situ p+‐type boron‐doped amorphous Si layers, the low pressure chemical vapor deposition (LPCVD) of in situ p+‐type B‐doped polycrystalline Si layers, and the LPCVD of intrinsic amorphous Si, subsequently ion‐implanted with boron. We observe the lowest J0e values of 3.8 fA cm−2 on thermally grown interfacial oxide on planar surfaces for the case of intrinsic amorphous Si deposited by LPCVD and subsequently implanted with boron. Also, we obtain a similar high passivation of p+‐type poly‐Si junctions on wet‐chemically grown oxides as well as for all the investigated polycrystalline‐Si deposition approaches. Conversely, on alkaline‐textured surfaces, J0e is at least 4 times higher compared to planar surfaces. This finding holds for all the junction preparation methods investigated. We show that the higher J0e on textured surfaces can be attributed to a poorer passivation of the p+ poly/c‐Si stacks on (111) when compared to (100) surfaces.

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Section: Introductionmentioning

confidence: 99%

On the recombination behavior of p⁺-type polysilicon on oxide junctions deposited by different methods on textured and planar surfaces

Larionova

Turcu

Reiter

et al. 2017

Phys. Status Solidi A

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confidence: 99%

Separating the two polarities of the POLO contacts of an 26.1%-efficient IBC solar cell

Hollemann

Haase

Rienäcker

et al. 2020

Sci Rep

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This is because the high conductivity of the poly-Si does not impede a transport limitation. Therefore, a separation of the n-type POLO (nPOLO) and p-type POLO (pPOLO) contact fingers is required [25][26][27][28][29] .In this work we employ a POLO junction scheme that consists of an initially full area intrinsic poly-Si (i poly-Si) layer that is locally doped by ion implantation. From process leanness point of view an attractive option to avoid these pn junctions in the poly-Si is to leave an (i) poly-Si region between emitter and base fingers. This is expected to result in lateral p(i)n poly-Si junction at the rear side of the IBC cell, which is connected in parallel to the nPOLO/p-type c-Si junctions ( Fig. 1a). By applying the described junction scheme we demonstrated a solar cell with an efficiency of 26.1% 11,21 .This concept was previously tested by other groups on precursor level 30 achieving a V OC of 682 mV with an pFF of 80% and on the cell level 27 yielding an efficiency of 18.4%. Both devices showed high ideality factors pointing to a non-ideal recombination in the space charge region. To evaluate why our cell, in contrast, does not suffer from a high ideality factor we perform a systematic study of the device physics of the resulting p(i)n poly-Si diodes.We quantify the defect density in our poly-Si layers prior and after hydrogenation using time-dependent photoluminescence decay measurements in the picosecond regime.As the purpose of the (i) poly-Si regions is to suppress high recombination currents across the p(i)n diode a large (i) poly-Si region is desirable. On the other hand, we observed a poor passivation quality of the c-Si absorber by the iPOLO on full-area lifetime test structures (see below). This is due to the moderate chemical passivation of SiO x on p-type Si, which further degrades when forming the nanometer-sized pinholes in the interfacial oxide 31 . This reasoning favors small (i) poly-Si widths. To find an optimum between these counteracting requirements, we experimentally vary the width of the (i) poly-Si region from nominal d gap = 0 µm up to 380 µm.We experimentally find that a width of the initially i poly-Si layer of d gap = 30 µm together with a high annealing temperature of over 1000 °C enables a record cell efficiency of 26.1%. From measurements on full area test structures and numerical device simulations we know that the surface recombination velocity at the intrinsic poly-Si is above 2000 cm/s and would limit the device efficiency to 15%. We conclude that the nominally intrinsic poly-Si layer is no longer intrinsic after the full cell process.We therefore investigate an inter-diffusion of dopants from the n-type and p-type doped fingers into the initially intrinsic poly-Si region by a lateral Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS) measurement. Combining all three aspects, we are, for the first time, able to present a comprehensive understanding of the working principle of high-efficient POLO IBC cells with p(i)n poly-Si diodes. Scientific RepoRtS |(202...

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“…To analyze the recombination behavior, we measure the spatially resolved charge carrier lifetime of the cell precursors during the cell process with the infrared lifetime mapping (ILM) method . To determine implied pseudo efficiencies, we perform this measurement at different illumination intensities to analyze the injection dependent recombination . The ILM measurement is firstly carried out in the state after junction formation, hydrogenation and the subsequent annealing.…”

Section: Methodsmentioning

confidence: 99%

“…10,11 To determine implied pseudo efficiencies, we perform this measurement at different illumination intensities to analyze the injection dependent recombination. 14 The ILM measurement is firstly carried out in the state after junction formation, hydrogenation and the subsequent annealing. The second measurement is done after contact opening, and the third measurement is done after finishing the cell.…”

Section: Measurementsmentioning

confidence: 99%

26.1%‐efficient POLO‐IBC cells: Quantification of electrical and optical loss mechanisms

Hollemann

Haase

Schäfer

et al. 2019

Progress in Photovoltaics

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We present experimental results for interdigitated back contacted (IBC) solar cells with passivating POLO contacts for both polarities with a nominal intrinsic poly‐Si region between them. We reach efficiencies of 26.1% and 24.9% on a 1.3 Ω cm and 80 Ω cm p‐type FZ wafer and 24.6% on a 2 Ω cm n‐type Cz wafer, respectively. The initially measured implied efficiency potentials of the cells after passivating the surfaces are very similar, namely, 26.8%, 26.8%, and 26.4%, respectively. We attribute the difference between the efficiency potential and the final current‐voltage measurement to degradation, perimeter, and series and shunt resistance losses, which we quantify by lifetime measurements. With these measurements in combination with a finite element simulation, we determine the surface recombination velocity in the nominal intrinsic poly‐Si region to be in the range from 13 to 21 cm s−1. Using the same approach, we analyze the increase of the front surface recombination velocity during cell processing from 2 to 10 cm s−1 for the 1.3 Ω cm and from 0.5 to 2.3 cm s−1 for the 80 Ω cm. This leads to the fact that cells fabricated on lowly doped bulk material are more vulnerable to a process‐induced degradation of the surface passivation quality. We further determine the theoretical limits of the cells by firstly idealizing the recombination (28% for 1.3 Ω cm and 28.2% for 80 Ω cm) and secondly also idealizing the optics of the solar cells (29.4% and 29.5%).

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Interdigitated back contact solar cells with polycrystalline silicon on oxide passivating contacts for both polarities

Cited by 78 publications

References 17 publications

On the recombination behavior of p⁺-type polysilicon on oxide junctions deposited by different methods on textured and planar surfaces

On the recombination behavior of p⁺-type polysilicon on oxide junctions deposited by different methods on textured and planar surfaces

Separating the two polarities of the POLO contacts of an 26.1%-efficient IBC solar cell

26.1%‐efficient POLO‐IBC cells: Quantification of electrical and optical loss mechanisms

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Interdigitated back contact solar cells with polycrystalline silicon on oxide passivating contacts for both polarities

Cited by 78 publications

References 17 publications

On the recombination behavior of p+-type polysilicon on oxide junctions deposited by different methods on textured and planar surfaces

On the recombination behavior of p+-type polysilicon on oxide junctions deposited by different methods on textured and planar surfaces

Separating the two polarities of the POLO contacts of an 26.1%-efficient IBC solar cell

26.1%‐efficient POLO‐IBC cells: Quantification of electrical and optical loss mechanisms

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On the recombination behavior of p⁺-type polysilicon on oxide junctions deposited by different methods on textured and planar surfaces

On the recombination behavior of p⁺-type polysilicon on oxide junctions deposited by different methods on textured and planar surfaces