With a global market share of about 90%, crystalline silicon is by far the most important photovoltaic technology today. This article reviews the dynamic field of crystalline silicon photovoltaics from a device-engineering perspective. First, it discusses key factors responsible for the success of the classic dopant-diffused silicon homojunction solar cell. Next it analyzes two archetypal high-efficiency device architectures – the interdigitated back-contact silicon cell and the silicon heterojunction cell – both of which have demonstrated power conversion efficiencies greater than 25%. Last, it gives an up-to-date summary of promising recent pathways for further efficiency improvements and cost reduction employing novel carrier-selective passivating contact schemes, as well as tandem multi-junction architectures, in particular those that combine silicon absorbers with organic–inorganic perovskite materials.

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High-efficiency crystalline silicon solar cells: status and perspectives

Excellent surface passivation of c-Si has been achieved by Al2O3 films prepared by plasma-assisted atomic layer deposition, yielding effective surface recombination velocities of 2 and 13cm∕s on low resistivity n- and p-type c-Si, respectively. These results obtained for ∼30nm thick Al2O3 films are comparable to state-of-the-art results when employing thermal oxide as used in record-efficiency c-Si solar cells. A 7nm thin Al2O3 film still yields an effective surface recombination velocity of 5cm∕s on n-type silicon.

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Ultralow surface recombination of c-Si substrates passivated by plasma-assisted atomic layer deposited Al2O3

In the 1980s, advances in the passivation of both cell surfaces led to the first crystalline silicon solar cells with conversion efficiencies above 20%. With today's industry trend towards thinner wafers and higher cell efficiency, the passivation of the front and rear surfaces is now also becoming vitally important for commercial silicon cells. This paper presents a review of the surface passivation methods used since the 1970s, both on laboratory-type as well as industrial cells. Given the trend towards lower-cost (but also lower-quality) Si materials such as block-cast multicrystalline Si, ribbon Si or thin-film polycrystalline Si, the most promising surface passivation methods identified to date are the fabrication of a p–n junction and the subsequent passivation of the resulting silicon surface with plasma silicon nitride as this material, besides reducing surface recombination and reflection losses, additionally provides a very efficient passivation of bulk defects. Copyright © 2000 John Wiley & Sons, Ltd.

Surface passivation of crystalline silicon solar cells: a review

Thin Al2O3 films with a thickness of 7–30 nm synthesized by plasma-assisted atomic layer deposition (ALD) were used for surface passivation of crystalline silicon (c-Si) of different doping concentrations. The level of surface passivation in this study was determined by techniques based on photoconductance, photoluminescence, and infrared emission. Effective surface recombination velocities of 2 and 6 cm/s were obtained on 1.9 Ω cm n-type and 2.0 Ω cm p-type c-Si, respectively. An effective surface recombination velocity below 1 cm/s was unambiguously obtained for nearly intrinsic c-Si passivated by Al2O3. A high density of negative fixed charges was detected in the Al2O3 films and its impact on the level of surface passivation was demonstrated experimentally. The negative fixed charge density results in a flat injection level dependence of the effective lifetime on p-type c-Si and explains the excellent passivation of highly B-doped c-Si by Al2O3. Furthermore, a brief comparison is presented between the ...

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Silicon surface passivation by atomic layer deposited Al2O3

Atomic-layer-deposited aluminium oxide (Al2O3) is applied as rear-surface-passivating dielectric layer to passivated emitter and rear cell (PERC)-type crystalline silicon (c-Si) solar cells. The excellent passivation of low-resistivity p-type silicon by the negative-charge-dielectric Al2O3 is confirmed on the device level by an independently confirmed energy conversion efficiency of 20·6%. The best results are obtained for a stack consisting of a 30 nm Al2O3 film covered by a 200 nm plasma-enhanced-chemical-vapour-deposited silicon oxide (SiOx) layer, resulting in a rear surface recombination velocity (SRV) of 70 cm/s. Comparable results are obtained for a 130 nm single-layer of Al2O3, resulting in a rear SRV of 90 cm/s. Copyright © 2008 John Wiley & Sons, Ltd.

Surface passivation of high‐efficiency silicon solar cells by atomic‐layer‐deposited Al2O3

In a recent letter [Lauinger et al., Appl. Phys. Lett. 68, 1232 (1996)] we have shown that record low effective surface recombination velocities Seff of 4 cm/s have been obtained at ISFH on low-resistivity (1 Ω cm) p-type crystalline silicon using microwave-excited remote plasma-enhanced chemical vapor deposition (RPECVD) of silicon nitride at low temperature (300–400 °C). As an important application, this technique allows a simple fabrication of rear-passivated high-efficiency silicon solar cells with monofacial or bifacial sensitivity. In this work, we present details of the required optimization of the PECVD parameters and a characterization of the resulting silicon nitride films. All deposition parameters are shown to strongly affect Seff as well as the stability of the films against the ultraviolet (UV) photons of terrestrial sunlight. A clear correlation between Seff and the film stoichiometry is observed, allowing a simple control and even a rough optimization of the surface passivation quality by ...

Optimization and characterization of remote plasma-enhanced chemical vapor deposition silicon nitride for the passivation of p-type crystalline silicon surfaces

Industrial high performance crystalline silicon solar cells and modules based on rear surface passivation technology

A comprehensive and systematic investigation of low-cost surface passivation technologies is presented for achieving high-performance silicon devices such as solar cells. Most commercial solar cells today lack adequate surface passivation, while laboratory cells use conventional furnace oxides (CFO) for high-quality surface passivation involving an expensive and lengthy high-temperature step. This investigation tries to bridge the gap between commercial and laboratory cells by providing fast, low-cost methods for effective surface passivation. This paper demonstrates for the first time, the efficacy of TiO/sub 2/, thin ( 15 for a 90 /spl Omega//sq. emitter, 2) reduce J/sub 0e/ by a factor of >3 for a 40 /spl Omega//sq, emitter, and 3) reduce S/sub back/ below 20 cm/s on 1.3 /spl Omega/cm p-Si. Furthermore, this double-layer RTO+SiN passivation is relatively independent of the deposition conditions (direct or remote) of the SiN film and is more stable under heat treatment than SiN or RTO alone. Model calculations are also performed to show that the RTO+SiN surface passivation scheme may lead to 17%-efficient thin screen-printed cells even with a low bulk lifetime of 20 /spl mu/s.

Comprehensive study of rapid, low-cost silicon surface passivation technologies

We have studied the surface passivation of silicon by deposition of silicon nitride (SiN) in an industrial-type inline plasma-enhanced chemical vapor deposition (PECVD) reactor designed for the continuous coating of silicon solar cells with high throughput. An optimization study for the passivation of low-resistivity p-type silicon has been performed exploring the dependence of the film quality on key deposition parameters of the system. With the optimized films, excellent passivation properties have been obtained, both on undiffused p-type silicon and on phosphorus-diffused n + emitters. Using a simple design, solar cells with conversion efficiencies above 20% have been fabricated to prove the efficacy of the inline PECVD SiN. The passivation properties of the films are on a par with those of high-quality films prepared in small-area laboratory PECVD reactors.

Jens Moschner

Papers

Optimization and characterization of remote plasma-enhanced chemical vapor deposition silicon nitride for the passivation of p-type crystalline silicon surfaces

Industrial high performance crystalline silicon solar cells and modules based on rear surface passivation technology

Comprehensive study of rapid, low-cost silicon surface passivation technologies

High-quality surface passivation of silicon solar cells in an industrial-type inline plasma silicon nitride deposition system

Recent Progress in the Surface Passivation of Silicon Solar Cells Using Silicon Nitride