TY - JOUR
T1 - Is carrier mobility a limiting factor for charge transfer in TiO2/Si devices? A study by transient reflectance spectroscopy
AU - Khan, Ramsha
AU - Pasanen, Hannu P.
AU - Ali-Löytty, Harri
AU - Ayedh, Hussein M.
AU - Saari, Jesse
AU - Vähänissi, Ville
AU - Valden, Mika
AU - Savin, Hele
AU - Tkachenko, Nikolai V.
N1 - Funding Information:
R.K. thanks Tampere University doctoral school, Finland and Kaute foundation, Finland for the funding. J.S. was supported by the Vilho, Yrjö and Kalle Väisälä Foundation of the Finnish Academy of Science and Letters . The authors acknowledge the financial support of the Academy of Finland both via the Flagship on Photonics Research and Innovation “PREIN” and via the project numbers 320164 (H. P. P., H. A.), and 331313 (V. V.). This work was supported by the Jane & Aatos Erkko Foundation, Finland (Project ‘Solar Fuels Synthesis’). The authors acknowledge the provision of facilities and technical support by Micronova Nanofabrication Centre in Espoo, Finland within the OtaNano research infrastructure at Aalto University.
Funding Information:
This document is the results of the research project funded by Academy of Finland.R.K. thanks Tampere University doctoral school, Finland and Kaute foundation, Finland for the funding. J.S. was supported by the Vilho, Yrjö and Kalle Väisälä Foundation of the Finnish Academy of Science and Letters. The authors acknowledge the financial support of the Academy of Finland both via the Flagship on Photonics Research and Innovation “PREIN” and via the project numbers 320164 (H. P. P. H. A.), and 331313 (V. V.). This work was supported by the Jane & Aatos Erkko Foundation, Finland (Project ‘Solar Fuels Synthesis’). The authors acknowledge the provision of facilities and technical support by Micronova Nanofabrication Centre in Espoo, Finland within the OtaNano research infrastructure at Aalto University.
Funding Information:
This document is the results of the research project funded by Academy of Finland .
Publisher Copyright:
© 2023 The Author(s)
PY - 2023/6
Y1 - 2023/6
N2 - TiO2 coatings are often deposited over silicon-based devices for surface passivation and corrosion protection. However, the charge transfer (CT) across the TiO2/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 TiO2/Si interface, transient reflectance (TR) spectroscopy was employed as a contact-free method to evaluate the impact of interfacial SiOx, heat-treatments, and other phenomena on the CT. Thin-film interference model was adapted to separate signals for Si and TiO2 and to estimate the number of transferred carriers. Charge transfer velocity was found to be 5.2 × 104 cm s−1 for TiO2 heat-treated at 300 °C, and even faster for amorphous TiO2 if the interfacial SiOx layer was removed using HF before TiO2 deposition. However, the interface is easily oversaturated because of slow carrier diffusion in TiO2 away from the TiO2/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 TiO2 due to back recombination via the interfacial SiOx, which is detrimental to TiO2/Si device performance.
AB - TiO2 coatings are often deposited over silicon-based devices for surface passivation and corrosion protection. However, the charge transfer (CT) across the TiO2/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 TiO2/Si interface, transient reflectance (TR) spectroscopy was employed as a contact-free method to evaluate the impact of interfacial SiOx, heat-treatments, and other phenomena on the CT. Thin-film interference model was adapted to separate signals for Si and TiO2 and to estimate the number of transferred carriers. Charge transfer velocity was found to be 5.2 × 104 cm s−1 for TiO2 heat-treated at 300 °C, and even faster for amorphous TiO2 if the interfacial SiOx layer was removed using HF before TiO2 deposition. However, the interface is easily oversaturated because of slow carrier diffusion in TiO2 away from the TiO2/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 TiO2 due to back recombination via the interfacial SiOx, which is detrimental to TiO2/Si device performance.
KW - Atomic layer deposition
KW - Charge transfer
KW - Photoelectrochemistry
KW - Titanium dioxide
KW - Transient reflectance spectroscopy
U2 - 10.1016/j.surfin.2023.102871
DO - 10.1016/j.surfin.2023.102871
M3 - Article
AN - SCOPUS:85152726275
SN - 2468-0230
VL - 38
JO - Surfaces and Interfaces
JF - Surfaces and Interfaces
M1 - 102871
ER -