High‐Performance TiO<sub>2</sub>‐Based Electron‐Selective Contacts for Crystalline Silicon Solar Cells

Yang, Xinbo; Bi, Qunyu; Ali, Haider; Davis, Kristopher O.; Schoenfeld, Winston V.; Weber, Klaus

doi:10.1002/adma.201600926

Cited by 327 publications

(408 citation statements)

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“…Maximization of the solar cell open-circuit voltage (V OC ) to record values of 750 mV [1] has been possible by combining two principles of solar cell design [2]: (1) , alkali salts [ 6 , 7 ] and transition metal oxides (TMOs) [ [8][9][10][11][12][13][14][15][16][17][18] ]. TMOs offer themselves as excellent candidates to substitute traditional c-Si dopants given their wide range of work function values (3 -7 eV) and marked p-or n-type semiconductivity [ 19 ].…”

Section: Introductionmentioning

confidence: 99%

Origin of passivation in hole-selective transition metal oxides for crystalline silicon heterojunction solar cells

et al. 2016

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Transition metal oxides (TMOs) have recently attracted interest as an alternative to boron/phosphorous doped layers in crystalline silicon heterojunction solar cells. In this work, the interface between n-type c-Si (n-Si) and three thermally evaporated TMOs (MoO 3 , WO 3 and V 2 O 5 ) was investigated by transmission electron microscopy and secondary ion-mass/x-ray photoelectron spectroscopy. For the oxides studied, chemical passivation of n-Si was attributed to an ultra-thin (1.9 -2.8 nm) SiO x~1.5 interlayer formed by chemical reaction, leaving oxygen-deficient species (MoO, WO 2 and VO 2 ) as byproducts. Field-effect passivation was also inferred from the inversion (hole-rich) layer induced on the n-Si surface, a result of Fermi level alignment between two materials with dissimilar electrochemical potentials (work function delta Δφ ≥1 eV). Therefore, the holeselective and passivating functionality of these TMOs, in addition to their ambient temperature processing, could prove an effective means to lower cost and simplify solar cell processing.

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Section: Introductionmentioning

confidence: 99%

Origin of passivation in hole-selective transition metal oxides for crystalline silicon heterojunction solar cells

et al. 2016

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“…Thin TiO2 films in amorphous phase can provide better Si surface passivation in the mechanisms of field-effect passivation and chemical passivation. The degradation of the surface passivation quality with increasing the TiO2 thickness could be caused by stress effects and phase transformation, which has been reported and proved [26,27,32]. Phase transformation of TiO2 at the interface could change the band structure and the interface trap density to decrease the field-effect passivation.…”

Section: Silicon Surface Passivation Of Ald Tio2mentioning

confidence: 99%

“…Heterogeneous nucleation and growth of anatase TiO 2 took place from the surface of the Si [31]. The phase transformation of the TiO 2 films from amorphous to anatase might reduce the filed-effect passivation of TiO 2 film (discuss in Section 3.2) [26,32]. Figure 2 shows the depth profile analysis of oxygen, silicon and hydrogen elements for 66-nm-thick TiO 2 films on silicon.…”

Section: Characterization Of Ald Tio 2 Thin Filmsmentioning

confidence: 99%

“…However, FGA at high temperatures will degrade the field-effect passivation of TiO 2 films due to the phase transformation from amorphous to anatase [26]. In order to study the thermal budget effect on the silicon surface passivation of TiO 2 films, one sample was deposited for 250 cycles without post-deposition annealing, and another was deposited for 250 cycles with post-deposition annealing at 200 • C for more 6000 s in the chamber.…”

Section: Silicon Surface Passivation Of Ald Tio2mentioning

confidence: 99%

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Atomic Layer Deposition TiO2 Films and TiO2/SiNx Stacks Applied for Silicon Solar Cells

et al. 2016

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Titanium oxide (TiO 2 ) films and TiO 2 /SiN x stacks have potential in surface passivation, anti-reflection coatings and carrier-selective contact layers for crystalline Si solar cells. A Si wafer, deposited with 8-nm-thick TiO 2 film by atomic layer deposition, has a surface recombination velocity as low as 14.93 cm/s at the injection level of 1.0 × 10 15 cm −3 . However, the performance of silicon surface passivation of the deposited TiO 2 film declines as its thickness increases, probably because of the stress effects, phase transformation, atomic hydrogen and thermal stability of amorphous TiO 2 films. For the characterization of 66-nm-thick TiO 2 film, the results of transmission electron microscopy show that the anatase TiO 2 crystallinity forms close to the surface of the Si. Secondary ion mass spectrometry shows the atomic hydrogen at the interface of TiO 2 and Si which serves for chemical passivation. The crystal size of anatase TiO 2 and the homogeneity of TiO 2 film can be deduced by the measurements of Raman spectroscopy and spectroscopic ellipsometry, respectively. For the passivating contacts of solar cells, in addition, a stack composed of 8-nm-thick TiO 2 film and a plasma-enhanced chemical-vapor-deposited 72-nm-thick SiN x layer has been investigated. From the results of the measurement of the reflectivity and effective carrier lifetime, TiO 2 /SiN x stacks on Si wafers perform with low reflectivity and some degree of surface passivation for the Si wafer.

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“…14 Moreover, when inserting an intrinsic a-Si:H layer into MoO x /n-Si heterojunctions for passivation, PCE as high as 22.5% has been recorded for this novel structure (MoO x /a − Si:H/n-Si) solar cells. 12 Analogously, TiO 2 exhibits superior electron-selective and surface passivation property, 8,9 proving dopant-free TMOs are ideal candidates for replacing doped a-Si:H.…”

Section: Introductionmentioning

confidence: 99%

Silicon based solar cells using a multilayer oxide as emitter

Bao

Liu

et al. 2016

AIP Advances

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In this work, n-type silicon based solar cells with WO3/Ag/WO3 multilayer films as emitter (WAW/n-Si solar cells) were presented via simple physical vapor deposition (PVD). Microstructure and composition of WAW/n-Si solar cells were studied by TEM and XPS, respectively. Furthermore, the dependence of the solar cells performances on each WO3 layer thickness was investigated. The results indicated that the bottom WO3 layer mainly induced band bending and facilitated charge-carriers separation, while the top WO3 layer degraded open-circuit voltage but actually improved optical absorption of the solar cells. The WAW/n-Si solar cells, with optimized bottom and top WO3 layer thicknesses, exhibited 5.21% efficiency on polished wafer with area of 4 cm2 under AM 1.5 condition (25 °C and 100 mW/cm2). Compared with WO3 single-layer film, WAW multilayer films demonstrated better surface passivation quality but more optical loss, while the optical loss could be effectively reduced by implementing light-trapping structures. These results pave a new way for dopant-free solar cells in terms of low-cost and facile process flow.

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High‐Performance TiO₂‐Based Electron‐Selective Contacts for Crystalline Silicon Solar Cells

Abstract: Thin TiO2 films are demonstrated to be an excellent electron-selective contact for crystalline silicon solar cells. An efficiency of 21.6% is achieved for crystalline silicon solar cells featuring a full-area TiO2 -based electron-selective contact.

Cited by 327 publications

References 27 publications

Origin of passivation in hole-selective transition metal oxides for crystalline silicon heterojunction solar cells

Origin of passivation in hole-selective transition metal oxides for crystalline silicon heterojunction solar cells

Atomic Layer Deposition TiO2 Films and TiO2/SiNx Stacks Applied for Silicon Solar Cells

Silicon based solar cells using a multilayer oxide as emitter

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High‐Performance TiO2‐Based Electron‐Selective Contacts for Crystalline Silicon Solar Cells

Abstract: Thin TiO2 films are demonstrated to be an excellent electron-selective contact for crystalline silicon solar cells. An efficiency of 21.6% is achieved for crystalline silicon solar cells featuring a full-area TiO2 -based electron-selective contact.

Cited by 327 publications

References 27 publications

Origin of passivation in hole-selective transition metal oxides for crystalline silicon heterojunction solar cells

Origin of passivation in hole-selective transition metal oxides for crystalline silicon heterojunction solar cells

Atomic Layer Deposition TiO2 Films and TiO2/SiNx Stacks Applied for Silicon Solar Cells

Silicon based solar cells using a multilayer oxide as emitter

Contact Info

Product

Resources

About

High‐Performance TiO₂‐Based Electron‐Selective Contacts for Crystalline Silicon Solar Cells