Dual Functional Dopant‐Free Contacts with Titanium Protecting Layer: Boosting Stability while Balancing Electron Transport and Recombination Losses

Liu, Zhaolang; Lin, Hao; Wang, Zhong Lin; Chen, Liyan; Wu, Taojian; Pang, Yicong; Cai, Lun; He, Jiasong; Peng, Shanglong; Shen, Hui; Gao, Pingqi

doi:10.1002/advs.202202240

Cited by 27 publications

(44 citation statements)

References 43 publications

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“…They feature nonsilicon materials with wide bandgap and high or low workfunction (WF). [6][7][8][9] Using the dopant-free contacts, it is expected to reduce the parasitic optical absorption and simplify the fabrication process as well as lower the cost. Furthermore, wide-bandgap materials are also beneficial in realizing the large asymmetry between electron and hole conductivity, thus realizing superior charge carrier selectivity.…”

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confidence: 99%

Perovskite‐Based Electron‐Selective Contacts for Silicon Solar Cells

et al. 2022

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Efficient carrier-selective contacts play significant roles in highperformance solar cells, which are responsible for the separation and collection of photogenerated charge carriers. Electronselective contacts only collect electrons and block holes, while hole-selective contacts are opposite. It is believed that the large asymmetry between electron and hole conductivity, together with a suitable band offset, is the key to realize efficient carrierselective contacts. [1,2] To date, all of the mainstream commercial crystalline silicon (c-Si) solar cells, that is, passivated emitter and rear cell (PERC) cells, [3] tunnel oxide passivating contact (TPOCon) cells, [4] and heterojunction with intrinsic thin layer (HIT) cells, [5] utilize either heavily doped c-Si films, poly-Si films, or amorphous Si films as carrier-selective contacts. Although they are efficient, any heavily doped Si suffers from parasitic optical absorption, due to their narrow bandgaps (<2 eV). Moreover, heavy doping also induces Auger recombination in PERC solar cells, which further limit the power conversion efficiency (PCE). [6] From manufacturing aspects, the heavy doping in silicon is either achieved by high-temperature diffusion (e.g., >800 °C for PERC cells and TOPCon cells) or relies on capital-intensive equipment (e.g., plasmaenhanced chemical vapor deposition [PECVD] for HIT cells).These disadvantages have sparked intensive exploration of dopant-free carrierselective materials to replace heavily doped Si thin layers. They feature nonsilicon materials with wide bandgap and high or low workfunction (WF). [6][7][8][9] Using the dopant-free contacts, it is expected to reduce the parasitic optical absorption and simplify the fabrication process as well as lower the cost. Furthermore, wide-bandgap materials are also beneficial in realizing the large asymmetry between electron and hole conductivity, thus realizing superior charge carrier selectivity. [2] Up to now, a lot of metal compounds, such as metal oxides, [10][11][12][13] fluorides, [14][15][16] nitrides, and oxynitride, [17][18][19] have been reported as efficient electron transport layers for c-Si solar cells. They typically have a small conduction band offset (ΔE C ) and large valance band offset (ΔE V ) with c-Si. Combining with low-WF metals, they can form excellent ihmic contacts with c-Si, making photogenerated electrons collected efficiently.Despite the successful demonstration of carrier selectivity, it is widely accepted that environmental and thermal stability remains one of the challenges for dopant-free contacts to be considered for industrial adoption. [20][21][22][23][24] A lot of dopant-free contacts are found to be sensitive to air exposure, especially when combined with heating, leading to the degradation of solar cell performance. [24][25][26][27][28][29] For example, ρ c of KF x /Al and CsF x /Al increase by more than one order of magnitude when exposed to air for 1000 h. [14] Furthermore, the V OC and FF of the c-Si solar cell using ZnO/LiF/Al as the electron-selecti...

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confidence: 99%

Perovskite‐Based Electron‐Selective Contacts for Silicon Solar Cells

et al. 2022

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“…The energy band structure of the TX-100 film was analyzed through ultraviolet photoelectron spectroscopy (UPS). The work function of the TX-100 film is 3.4 eV as indicated by the secondary electron cutoff region ( Figure 1 a), which is lower than the work function of Al [ 14 ]. Figure 1 b shows the valence band spectrum and the valance band maximum of the TX-100 film is situated 2.6 eV below the Fermi level, which is good for blocking minority carriers.…”

Section: Resultsmentioning

confidence: 99%

“…The Al directly contacted heterojunction solar cell shows poor performance as the V oc , J sc , FF, and PCE are 375 mV, 37.5 mA·cm −2 , 51.6%, and 7.3%, respectively. The a-Si:H(i)/Al direct contact is not a good idea [ 14 , 43 , 44 ] as the metal atoms can easily diffuse through the thin a-Si:H layer and destroy the passivation [ 14 , 45 ]. The a-Si:H(i)/TX-100/Al contact demonstrates good performance, showing V oc close to 700 mV and the champion PCE of 20.4%, which is significant in similar investigations [ 25 , 27 ].…”

Section: Resultsmentioning

confidence: 99%

“…In addition, these materials can be easily deposited by thermal evaporation. As for dopant-free electron-selective contacts, halides of alkaline (earth) metals and rare earth metals such as LiF x [ 13 , 14 ], CsF x [ 15 ], MgF x [ 16 ], CeF x [ 17 ], and GdF x [ 18 ] are the most intensively investigated system. Contact resistivity as low as ~1 mΩ·cm 2 has been reported [ 19 ].…”

Section: Introductionmentioning

confidence: 99%

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A High-Quality Dopant-Free Electron-Selective Passivating Contact Made from Ultra-Low Concentration Water Solution

Zeng

Cai²,

Wang

et al. 2022

Nanomaterials

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Crystalline silicon solar cells produced by doping processes have intrinsic shortages of high Auger recombination and/or severe parasitic optical absorption. Dopant-free carrier-selective contacts (DF-CSCs) are alternative routines for the next generation of highly efficient solar cells. However, it is difficult to achieve both good passivating and low contact resistivity for most DF-CSCs. In this paper, a high-quality dopant-free electron-selective passivating contact made from ultra-low concentration water solution is reported. Both low recombination current (J0) ~10 fA/cm2 and low contact resistivity (ρc) ~31 mΩ·cm2 are demonstrated with this novel contact on intrinsic amorphous silicon thin film passivated n-Si. The electron selectivity is attributed to relieving of the interfacial Fermi level pinning because of dielectric properties (decaying of the metal-induced gap states (MIGS)). The full-area implementation of the novel passivating contact shows 20.4% efficiency on a prototype solar cell without an advanced lithography process. Our findings offer a very simple, cost-effective, and efficient solution for future semiconductor devices, including photovoltaics and thin-film transistors.

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“…Over the past 5 years, DASH solar cells have shown a substantial increase in PCE, from 11.2% to 21.4% 51,52 . By combining with the IBC architecture, the PCE of DASH solar cells was further boosted to 23.61% 53 …”

Section: Introductionmentioning

confidence: 99%

Dopant‐free passivating contacts for crystalline silicon solar cells: Progress and prospects

Wang

Zhang

et al. 2022

EcoMat

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The evolution of the contact scheme has driven the technology revolution of crystalline silicon (c-Si) solar cells. The state-of-the-art high-efficiency c-Si solar cells such as silicon heterojunction (SHJ) and tunnel oxide passivated contact (TOPCon) solar cells are featured with passivating contacts based on doped Si thin films, which induce parasitic optical absorption loss and require capitalintensive deposition processes involving flammable and toxic gasses. A promising solution to tackle this problem is to employ dopant-free passivating contact, involving the use of transparent and cost-effective wide band gap materials. In this review, we first introduce the dopant-free passivating contact, from carrier transport mechanisms, material classification to evaluation methods. Then we focus on the advances in different strategies to improve cell performance, including material property optimization, structural and interfacial engineering, as well as various post-treatments. At the end, the challenge and perspective of dopant-free passivating contact c-Si solar cells are discussed.

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Dual Functional Dopant‐Free Contacts with Titanium Protecting Layer: Boosting Stability while Balancing Electron Transport and Recombination Losses

Cited by 27 publications

References 43 publications

Perovskite‐Based Electron‐Selective Contacts for Silicon Solar Cells

Perovskite‐Based Electron‐Selective Contacts for Silicon Solar Cells

A High-Quality Dopant-Free Electron-Selective Passivating Contact Made from Ultra-Low Concentration Water Solution

Dopant‐free passivating contacts for crystalline silicon solar cells: Progress and prospects

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