Abstract Passivating contacts are an important technological innovation for crystalline silicon (c-Si) solar cells that can deliver efficiencies of over 24% in mass production. In this study, we comprehensively analyze n-type bifacial c-Si solar cells with rear side SiOx/phosphorus-doped (n+) poly-Si passivating contacts (monoPoly™ cells) with varying thicknesses (50–250 nm) of the n+ poly-Si layer. The poly-Si layers are deposited by low-pressure chemical vapor deposition (LPCVD) and then phosphorus doped ex-situ in a diffusion furnace. The ex-situ doping is carefully optimized for each individual thickness to achieve a step-function-like doping profile. Excellent passivation properties are achieved with the SiOx/n+ poly-Si stack, with a dark saturation current density of only 1 fA/cm2 for 150 nm n+ poly-Si layers. Metallization is realized by screen printing using commercially available fire-through pastes. Very low dark saturation current densities of

Development of thin polysilicon layers for application in monoPoly (TM) cells with screen-printed and fired metallization

Photovoltaic (PV) technology is ready to become one of the main energy sources of, and contributers to, carbon neutrality by the mid‐21st century. In 2020, a total of 135 GW of PV modules were produced. Crystalline silicon solar cells dominate the world's PV market due to high power conversion efficiency, high stability, and low cost. Silicon heterojunction (SHJ) solar cells are one of the promising technologies for next‐generation crystalline silicon solar cells. Compared to the commercialized homojunction silicon solar cells, SHJ solar cells have higher power conversion efficiency, lower temperature coefficient, and lower manufacturing temperatures. Recently, several new record efficiencies have been achieved. To meet the continued demand for high‐efficiency solar cells, expectations for large‐scale mass production of SHJ solar cells are rising. To approach the efficiency limit and industrialization of SHJ solar cells, serious attempts have been made, yielding higher short‐circuit current, open‐circuit voltage, and fill factor. In this article, these recent advancements are reviewed, which reveals the future roadmap for approaching the efficiency limit.

Toward Efficiency Limits of Crystalline Silicon Solar Cells: Recent Progress in High‐Efficiency Silicon Heterojunction Solar Cells

Passivating contact crystalline silicon solar cells are among the most promising industrially feasible photovoltaic (PV) technologies and require excellent physical contacts to handle device performance. Here, we report a versatile polysilicon (poly-Si) film intentionally doped with carbon (C) to suppress blistering and improve physical contacts. Our investigations of blistering mechanisms reveal that the reduced crystallization fraction of poly-Si in conjunction with the suppressed level of hydrogen release should primarily be responsible for the blistering-free appearance of the C-doped poly-Si films. Moreover, additional advantages of high-quality passivation with a high implied open-circuit voltage (iVoc) exceeding 750 mV and an excellent optical response in the infrared band with a net current-density gain of 0.31 mA cm−2 are endowed to the C-doped poly-Si films. Consequently, the proof-of-concept devices featuring C-doping show a champion efficiency of 24.27%, which is 1.18% higher than that of the C-free counterparts (23.09%). Also, we present a certified efficiency of 23.82%, suggesting that the C-doped poly-Si has the potential to achieve high-efficiency c-Si solar cells.

Dual-functional carbon-doped polysilicon films for passivating contact solar cells: regulating physical contacts while promoting photoelectrical properties

Silicon heterojunction solar cells: Techno-economic assessment and opportunities

Passivating contacts for high-efficiency silicon-based solar cells: From single-junction to tandem architecture

Polysilicon passivated junctions: The next technology for silicon solar cells?

The year 2014 marks the point when silicon solar cells surpassed the 25% efficiency mark. Since then, all devices exceeding this mark, both small and large area, with contacts on both sides of the silicon wafer or just at the back, have utilized at least one passivating contact. Here, a passivating contact is defined as a group of layers that simultaneously provide selective conduction of charge carriers and effective passivation of the silicon surface. The widespread success of passivating contacts has prompted increased research into ways in which carrier‐selective junctions can be formed, yielding a diverse range of approaches. This paper seeks to classify passivating contact solar cells into three families, according to the material used for charge‐carrier selection: doped amorphous silicon, doped polycrystalline silicon, and metal compounds/organic materials. The paper tabulates their current efficiency values, discusses distinctive features, advantages, and limitations, and highlights promising opportunities going forth towards even higher conversion efficiencies.

https://onlinelibrary.wiley.com/doi/pdfdirect/10.1002/pip.3574

Silicon solar cells with passivating contacts: Classification and performance

The self-terminated, layered structure of van der Waals materials introduces fundamental advantages for infrared (IR) optoelectronic devices. These are mainly associated with the potential for low noise while maintaining high internal quantum efficiency when reducing IR absorber thicknesses. In this study, we introduce a new van der Waals material candidate, zirconium germanium telluride (ZrGeTe4), to a growing family of promising IR van der Waals materials. We find the bulk form ZrGeTe4 has an indirect band edge around ∼0.5 eV, in close agreement with previous theoretical predictions. This material is found to be stable up to 140 °C and shows minimal compositional variation even after >30 days storage in humid air. We demonstrate simple proof-of-concept broad spectrum photodetectors with responsivities above 0.1 AW-1 across both the visible and short-wave infrared wavelengths. This corresponds to a specific detectivity of ∼109 cm Hz1/2 W-1 at λ = 1.4 μm at room temperature. These devices show a linear photoresponse vs illumination intensity relationship over ∼4 orders of magnitude, and fast rise/fall times of ∼50 ns, also verified by a 3 dB roll-off frequency of 5.9 MHz. As the first demonstration of photodetection using ZrGeTe4, these characteristics measured on a simple proof-of-concept device show the exciting potential of the ZrGeTe4 for room temperature IR optoelectronic applications.

Visible to Short-Wave Infrared Photodetectors Based on ZrGeTe4 van der Waals Materials.

Temperature‐dependent performance of silicon heterojunction solar cells with transition‐metal‐oxide‐based selective contacts

This article presents a comprehensive study regarding the impact of the Al electrode on the surface passivation of three TiOx‐based passivating selective contacts: TiOx:Al/LiFx/Al,TiOx/LiFx/Al, and a‐Si/TiOx:Al/LiFx/Al. A deterioration in passivation is recorded after the deposition of the Al electrode at close to room temperature, where the deterioration correlated to the Al thickness. A thin Al (10 nm) electrode resulted in the most severe passivation decline, while samples with a 100 nm Al electrode showed much less passivation deterioration. Furthermore, it is found that a low‐temperature annealing step led to a partial recovery of the passivation, particularly in the case of TiOx:Al/LiFx/Al and a‐Si/TiOx:Al/LiFx/Al contacts. The presented discovery in this article provides crucial insight into the importance of characterization and evaluation of passivating contacts, which is demonstrated here to be highly sensitive to the deposited metal thickness and the interfacial layers, as well as to the post‐deposition annealing.

https://onlinelibrary.wiley.com/doi/pdfdirect/10.1002/pssr.202200304

Jesús Ibarra Michel

Papers

Polysilicon passivated junctions: The next technology for silicon solar cells?

Silicon solar cells with passivating contacts: Classification and performance

Visible to Short-Wave Infrared Photodetectors Based on ZrGeTe4 van der Waals Materials.

Temperature‐dependent performance of silicon heterojunction solar cells with transition‐metal‐oxide‐based selective contacts

Effect of Al Electrodes on Surface Passivation of TiOx Selective Heterocontacts for Si Solar Cells