Sputtered Ultrathin TiO2 as Electron Transport Layer in Silicon Heterojunction Solar Cell Technology

Abstract

This work presents the implementation of ultrathin TiO2 films, deposited at room temperature by radio-frequency magnetron sputtering, as electron-selective contacts in silicon heterojunction solar cells. The effect of the working pressure on the properties of the TiO2 layers and its subsequent impact on the main parameters of the device are studied. The material characterization revealed an amorphous structure regardless of the working pressure; a rougher surface; and a blue shift in bandgap in the TiO2 layer deposited at the highest-pressure value of 0.89 Pa. When incorporated as part of the passivated full-area electron contact in silicon heterojunction solar cell, the chemical passivation provided by the intrinsic a-Si:H rapidly deteriorates upon the sputtering of the ultra-thin TiO2 films, although a short anneal is shown to restore much of the passivation lost. The deposition pressure and film thicknesses proved to be critical for the efficiency of the devices. The film thicknesses below 2 nm are necessary to reach open-circuit values above 660 mV, regardless of the deposition pressure. More so, the fill-factor showed a strong dependence on deposition pressure, with the best values obtained for the highest deposition pressure, which we correlated to the porosity of the films. Overall, these results show the potential to fabricate silicon solar cells with a simple implementation of electron-selective TiO2 contact deposited by magnetron sputtering. These results show the potential to fabricate silicon solar cells with a simple implementation of electron-selective TiO2 contact.

Atom-to-Device Simulation of MoO3/Si Heterojunction Solar Cell

“…The efficiency of the homojunction silicon-based solar cell does not exceed 29% according to the Shockley–Quisser limit [ 22 ]. Therefore, various silicon-based heterojunction solar cells are being designed [ 23 ]. ZnO and perovskite materials coated on the silicon surface as an emitter layer have been found to increase their efficiency [ 24 ].…”

Reduced Work Function in Anatase ⟨101⟩ TiO2 Films Self-Doped by O-Vacancy-Dependent Ti3+ Bonds Controlling the Photocatalytic Dye Degradation Performance

“…All of the films had an average transmission of around 80% in the visible spectrum. The Lambert–Beer law was used to calculate the optical absorption coefficients (α) as a function of the wavelength of the films, where T represents the transmittance% and t denotes the film thickness. The variation of the absorption coefficient follows Tauc’s relation α = 2.303 t ( 2 − log ⁡ T ) …”

“…In this work, when all other parameters were kept fixed, only the sputtering gas pressure was varied, which caused significant changes in the films’ structural and optoelectronic properties. The sputtering pressure influenced the mean free path (λ) of the particles, following the relation λ = 2.33 × 10 − 20 T p δ m 2 where T is the temperature, p denotes the sputtering pressure, and m is the molecular diameter. , As a result, when the sputtering pressure rises, the reduced mean free path increases the frequency of collision of the sputtered Ti atoms with Ar and O atoms in the plasma, subsequently forming Ti–O bonds. These large numbers of collisions prevent the Ti and TiO moieties from reaching the substrate surface.…”

“…TiO 2 is a material possessing a wide variety of qualities, including excellent chemical inertness, superior photocatalytic activity, good optical transmittance with a high refractive index in the visible range, and strong mechanical hardness. − It is widely used in photoconversion-related issues, e.g., photodetectors, photocatalysis, and resistive switching devices, as a passivation layer in solar cell devices, high-K gate dielectric for the transistors, etc. − …”

“…where T is the temperature, p denotes the sputtering pressure, and m is the molecular diameter. 9,69 As a result, when the sputtering pressure rises, the reduced mean free path increases the frequency of collision of the sputtered Ti atoms with Ar and O atoms in the plasma, subsequently forming Ti−O bonds. These large numbers of collisions prevent the Ti and TiO moieties from reaching the substrate surface.…”