Interface analysis and intrinsic thermal stability of MoOx based hole-selective contacts for silicon heterojunction solar cells

Cho, Jinyoun; Nawal, Neerja; Hadipour, Afshin; Payo, María Recamán; Heide, Arvid van der; Radhakrishnan, Hariharsudan Sivaramakrishnan; Debucquoy, Maarten; Gordon, Ivan; Szlufcik, Jozef; Poortmans, Jef

doi:10.1016/j.solmat.2019.110074

Cited by 35 publications

(37 citation statements)

References 45 publications

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“…Particularly, poor V OC are measured (<665 mV) for the thinnest MoO x layer tested, while V OC increases when thicker layers are used. As similarly reported in Cho et al, 50 in the range of 5–8 nm, the V OC reaches a maximum. Above this value, V OC decreases.…”

Section: Solar Cell Resultssupporting

confidence: 85%

“…We do not ascribe these low parameters to the thermal budget during the metallization because the process temperature is kept at a relatively low temperature (170°C) which is identified as optimal 50 …”

Section: Solar Cell Resultsmentioning

confidence: 99%

“…The simulations are carried out using TCAD Sentaurus device simulator 55 running drift‐diffusion models previously validated for SHJ solar cells 56,57 . The structure includes a n‐type c‐Si absorber passivated by a 5 nm thick (i)a‐Si:H layer and coated by a MoO x (3–9 nm) and a thin SiO 2 layer at the (i)a‐Si:H/MoO x interface that is formed during the evaporation process as confirmed by other groups 49–51,58 . The front contact is then completed with ITO film (65 nm).…”

Section: Experimental and Simulation Methodsmentioning

confidence: 99%

“…Additionally, several groups 49–52 report the formation of a relatively thick 2‐ to 3‐nm sub‐stoichiometric silicon oxide (SiO 2 ) interlayer at the (i)a‐Si:H/MoO x interface in the as‐deposited state. More controversial is the instance of MoO x in stack with (i)a‐Si:H or indium tin oxide (ITO).…”

Section: Introductionmentioning

confidence: 99%

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Strategy to mitigate the dipole interfacial states in (i)a‐Si:H/MoO_x passivating contacts solar cells

Mazzarella

Alcañiz

Procel

et al. 2020

Progress in Photovoltaics

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Molybdenum oxide (MoOx) is attractive for applications as hole‐selective contact in silicon heterojunction solar cells for its transparency and relatively high work function. However, the integration of MoOx stacked on intrinsic amorphous silicon (i)a‐Si:H layer usually exhibits some issues that are still not fully solved resulting in degradation of electrical properties. Here, we propose a novel approach to enhance the electrical properties of (i)a‐Si:H/MoOx contact. We manipulate the (i)a‐Si:H interface via plasma treatment (PT) before MoOx deposition minimizing the electrical degradation without harming the optical response. Furthermore, by applying the optimized PT, we can reduce the MoOx thickness down to 3.5 nm with both open‐circuit voltage and fill factor improvements. Our findings suggest that the PT mitigates the decrease of the effective work function of the MoOx (WFMoOx) thin layer when deposited on (i)a‐Si:H. To support our hypothesis, we carry out electrical simulations inserting a dipole at the (i)a‐Si:H/MoOx interface accounting the attenuation of WFMoOx caused by both MoOx thickness and dipole. Our calculations confirm the experimental trends and thus provide deep insight in critical transport issues. Temperature‐dependent J‐V measurements demonstrate that the use of PT improves the energy alignment for an efficient hole transport.

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Section: Solar Cell Resultssupporting

confidence: 85%

Section: Solar Cell Resultsmentioning

confidence: 99%

Section: Experimental and Simulation Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Strategy to mitigate the dipole interfacial states in (i)a‐Si:H/MoO_x passivating contacts solar cells

Mazzarella

Alcañiz

Procel

et al. 2020

Progress in Photovoltaics

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“…This allows the transportation of holes across the interface by keeping contact resistance to the minimum, hence, MoO x is also termed as a holeselective layer. In general, MoO x is a desirable candidate for DASH solar cells not only because of its larger work function values but also because it can be deposited at a relatively low temperature of <200 C. 36 Various TMO counterparts such as V 2 O 5 and WO 3 have higher evaporation temperatures that increase oxygen depletion as well as adding to the heating of a treated substrate, thereby making the process a thermal-intensive one. These factors corroborate our assertion that MoO x is a worthy contender to be employed as a dopant-free hole-selective layer for DASH solar cell applications.…”

Section: Introductionmentioning

confidence: 99%

Numerical analysis of dopant‐free asymmetric silicon heterostructure solar cell with SiO ₂ as passivation layer

et al. 2020

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Conventional silicon heterojunction solar cells employ defects-prone a-Si:H layers for junction formation and passivation purposes. Substituting these layers with hole-selective MoO x and electron-selective TiO x can reduce parasitic absorption and energy band offsets issues associated with doped silicon films. In this work, dopant-free asymmetric heterostructure Si solar cells are studied with and without SiO 2 passivation layer, and their performance has been compared. The inclusion of ultrathin SiO 2 insulator as a passivation layer promotes significant band bending that induces interface inversion of crystalline silicon as well as maintains the electric field required to tunnel charge carriers. The energy band diagram studies and variation of oxide thickness show that the IV characteristics of the solar cell critically depend on the insulator thickness; as the carriers tunnelling through the insulator becomes negligible at larger thicknesses. The simulated structure with MoO x as front holeselective contact and without any passivation exhibited conversion efficiency of 15.73%, which improved to 18.69% by incorporating passivated a-Si:H. However, by employing rear SiO 2 /TiO x stack with the front SiO 2 /MoO x , the device performance enhanced to open-circuit voltage of 785 mV, short-circuit current density of 41 mA/cm 2 , fill factor of 77%, and simulated conversion efficiency of 24.83%, which is~10% enhancement in the performance as compared to reference device employing traditional a-Si:H with dopant-free films. Novelty Statement For the first time, a dopant-free asymmetric silicon heterostructure solar cell (DASH) employing silicon oxide (SiO 2) as a passivation layer has been physically modelled using Silvaco TCAD. The dopant-free MoO x and TiO x as holeand electron-selective contacts have been incorporated. An ultrathin SiO 2 promotes band bending that induces interface inversion of absorber as well as facilitating carrier tunnelling. An efficiency of 24.83% has been numerically attained which is the best performance among DASH structures designed with oxide passivation. The 2-D cross-section view of the proposed device employing dopant-free layers and oxide passivated film is illustrated in Figure 1 for which we have applied memory intensive numerical method based on the computation of Poisson, charge transport and continuity equations in the Silvaco ATLAS

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Effective Hydrogenation Strategies to Boost Efficiency over 20% for Crystalline Silicon Solar Cell with Al₂O₃/Cu₂O Passivating Contact

Liu

Lin

et al. 2022

Adv Funct Materials

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Passivation interlayers such as Al 2 O 3 are required to improve the hole selectivity of dopant-free passivating contact based on transition metal oxides. For the interlayer to provide low surface recombination as in conventional silicon heterojunctions (SHJs) or tunnel oxide passivated contact (TOPCon) technologies, "hydrogenation" strategies to effectively introduce hydrogen in passivation interlayers while being compatible with transition metal oxides (TMOs) are urgently sought after. In this work, an easy-to-implement strategy to successfully incorporate extra hydrogen in the Al 2 O 3 passivation layer is developed. The chemical and field-effect passivation mechanisms of the extra hydrogen are revealed via comprehensive experimental analyses and density functional theory calculations. By implementing H-Al 2 O 3 with Cu 2 O as the hole-selective rear contact in p-type crystalline silicon (c-Si) solar cells, a remarkable efficiency of 20.35% is achieved (fill factor of 84.76%). The study highlights a promising approach to improve the passivation quality of dielectric interlayers and boost the performance of dopant-free c-Si solar cells to compete against mainstream c-Si photovoltaics technologies.

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Interface analysis and intrinsic thermal stability of MoOx based hole-selective contacts for silicon heterojunction solar cells

Cited by 35 publications

References 45 publications

Strategy to mitigate the dipole interfacial states in (i)a‐Si:H/MoO_x passivating contacts solar cells

Strategy to mitigate the dipole interfacial states in (i)a‐Si:H/MoO_x passivating contacts solar cells

Numerical analysis of dopant‐free asymmetric silicon heterostructure solar cell with SiO ₂ as passivation layer

Effective Hydrogenation Strategies to Boost Efficiency over 20% for Crystalline Silicon Solar Cell with Al₂O₃/Cu₂O Passivating Contact

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Interface analysis and intrinsic thermal stability of MoOx based hole-selective contacts for silicon heterojunction solar cells

Cited by 35 publications

References 45 publications

Strategy to mitigate the dipole interfacial states in (i)a‐Si:H/MoOx passivating contacts solar cells

Strategy to mitigate the dipole interfacial states in (i)a‐Si:H/MoOx passivating contacts solar cells

Numerical analysis of dopant‐free asymmetric silicon heterostructure solar cell with SiO 2 as passivation layer

Effective Hydrogenation Strategies to Boost Efficiency over 20% for Crystalline Silicon Solar Cell with Al2O3/Cu2O Passivating Contact

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Product

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Strategy to mitigate the dipole interfacial states in (i)a‐Si:H/MoO_x passivating contacts solar cells

Strategy to mitigate the dipole interfacial states in (i)a‐Si:H/MoO_x passivating contacts solar cells

Numerical analysis of dopant‐free asymmetric silicon heterostructure solar cell with SiO ₂ as passivation layer

Effective Hydrogenation Strategies to Boost Efficiency over 20% for Crystalline Silicon Solar Cell with Al₂O₃/Cu₂O Passivating Contact