Gadolinium Fluoride as a High-Thickness-Tolerant Electron-Selective Contact Material for Solar Cells

Chen, Nuo; Cai, Lun; Xie, Fangyan; Wang, Wenxian; Wei, Huiqi; Hong, Yang; Shen, Hui; Liang, Zongcun

doi:10.1021/acsaem.1c03919

Cited by 16 publications

(12 citation statements)

References 48 publications

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“…the degradation of ZnO-based electron-selective contacts was significantly mitigated, maintaining over 93% of the initial V OC and over 88% of the initial FF after being exposed to air for 380 h. [29] In addition, several other electron-selective contacts have been tested either at room temperature or at 85 °C for 1000 h and show improved long-term stability. [23,28,30,31] Yet, more efforts are still needed on this aspect.…”

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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 test structure of TLM is shown in Figure 2 b. A champion ρ c value of 0.31 mΩ·cm 2 is achieved, lower than most reported structures [ 17 , 18 , 19 , 39 ]. The contact resistance increases significantly once the optimal concentration (~4 mg/mL) deviates as shown in Figure 2 c.…”

Section: Resultsmentioning

confidence: 77%

“…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%

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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“…Although there still exists some contention as to the mechanism of the high electron conductivity across this interface, [59,60,61] the formation of a low-work-function electrode have attributed as the most important consequence in most studies (such as LiF x and TiO x ). [26,42,62,63] Hence resulting in a significant increase of V oc to 630 mV, FF to 82.5%, and J sc to 38.4 mA cm −2 . The ultrathin SiO x layer annealed with forming gas was inserted, which provides chemical passivation.…”

Section: Proof-of-concept Solar Cellsmentioning

confidence: 99%

“…It is well known that MoO x , [27][28][29] WO x , [30] V 2 O 5 [31,32] and NiO x [33,34] have the property of high-work function as superior hole selective materials. And LiF x , [35] TiO x , [36,37] MgO x , [38] In 2 S 3 , [39] EuF x , [40] MgF x , [41] GdF x [42] have the property of low-work function as electron selective materials. However, it is important to note that the low efficiency of full-area contact and dopant-free crystalline silicon solar cells limits their industrialization, and the well-known LiF x is a safety risk for both experimental and industrial applications due to its high toxicity.…”

Section: Introductionmentioning

confidence: 99%

A Novel Ultra‐Low Work Function TbF_x for High Efficiency Dopant‐Free Silicon Solar Cells

Wei

Meng

Liu

et al. 2023

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The ability of carrier selective contact is mainly determined by the surface passivation and work function for dopant‐free materials applied in crystalline silicon (c‐Si) solar cells, which have received considerable attention in recent years. In this contribution, a novel electron‐selective material, lanthanide terbium trifluoride (TbFx), with an ultra‐low work function of 2.4 eV characteristic, is presented, allowing a low contact resistivity (ρc) of ≈3 mΩ cm2. Additionally, the insertion of ultrathin passivated SiOx layer deposited by PECVD between TbFx and n‐Si resulted in ρc only increase slightly. SiOx/TbFx stack eliminated fermi pinning between aluminum and n‐type c‐Si (n‐Si), which further enhanced the electron selectivity of TbFx on full‐area contacts to n‐Si. Last, SiOx/TbFx/Al electron‐selective contacts significantly improves the open circuit voltage (Voc) for silicon solar cells, but rarely impacts the short circuit current (Jsc) and fill factor (FF), thus champion efficiency cell achieved approaching 22% power conversion efficiency (PCE). This study indicates a great potential for using lanthanide fluorides as electron‐selective material in photovoltaic devices.

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Gadolinium Fluoride as a High-Thickness-Tolerant Electron-Selective Contact Material for Solar Cells

Cited by 16 publications

References 48 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

A Novel Ultra‐Low Work Function TbF_x for High Efficiency Dopant‐Free Silicon Solar Cells

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Gadolinium Fluoride as a High-Thickness-Tolerant Electron-Selective Contact Material for Solar Cells

Cited by 16 publications

References 48 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

A Novel Ultra‐Low Work Function TbFx for High Efficiency Dopant‐Free Silicon Solar Cells

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A Novel Ultra‐Low Work Function TbF_x for High Efficiency Dopant‐Free Silicon Solar Cells