Is Carrier Mobility a Limiting Factor for Charge Transfer in Tio2/Si Devices? A Study by Transient Reflectance Spectroscopy
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Volume Title
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
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Date
2023-06
Major/Subject
Mcode
Degree programme
Language
en
Pages
12
Series
Surfaces and Interfaces, Volume 38
Abstract
TiO 2 coatings are often deposited over silicon-based devices for surface passivation and corrosion protection. However, the charge transfer (CT) across the TiO 2/Si interface is critical as it may instigate potential losses and recombination of charge carriers in optoelectronic devices. Therefore, to investigate the CT across the TiO 2/Si interface, transient reflectance (TR) spectroscopy was employed as a contact-free method to evaluate the impact of interfacial SiO x, heat-treatments, and other phenomena on the CT. Thin-film interference model was adapted to separate signals for Si and TiO 2 and to estimate the number of transferred carriers. Charge transfer velocity was found to be 5.2 × 10 4 cm s −1 for TiO 2 heat-treated at 300 °C, and even faster for amorphous TiO 2 if the interfacial SiO x layer was removed using HF before TiO 2 deposition. However, the interface is easily oversaturated because of slow carrier diffusion in TiO 2 away from the TiO 2/Si interface. This inhibits CT, which could become an issue for heavily concentrated solar devices. Also, increasing the heat-treatment temperature from 300 °C to 550 °C has only little impact on the CT time but leads to reduced carrier lifetime of ¡3 ns in TiO 2 due to back recombination via the interfacial SiO x, which is detrimental to TiO 2/Si device performance.Description
Keywords
Transient reflectance spectroscopy, Charge transfer, Titanium dioxide, Photoelectrochemistry, Atomic layer deposition
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Citation
Khan , R , Pasanen , H , Ali-Löytty , H , Ayedh , H , Saari , J , Vähänissi , V , Valden , M , Savin , H & Tkachenko , N V 2023 , ' Is Carrier Mobility a Limiting Factor for Charge Transfer in Tio2/Si Devices? A Study by Transient Reflectance Spectroscopy ' , Surfaces and Interfaces , vol. 38 , 102871 . https://doi.org/10.1016/j.surfin.2023.102871
