Piezoelectrically enhanced pn junctions in photovoltaic systems

Newswise — Photoelectrochemical (PEC) water splitting is a potentially feasible strategy for converting solar energy into green hydrogen. However, current PEC systems suffer from relatively low charge separation efficiency and sluggish water oxidation reaction, which prevent them from meeting the needs of practical applications. A major hurdle, such as achieving effective spatial charge separation, is critical to achieving efficient solar conversion.

Heterojunction engineering is one of the most promising methods for space charge separation, although the efficiency of heterojunction carrier separation is limited due to energy band matching or interfacial and structural compatibility between different semiconductors. Meanwhile, it was proved that the construction of pn homojunction in finely controlled dopant or defect semiconductors was possible, but the phenomenon that neutralizes the interfacial electric field during the transfer process by the rapid accumulation of carriers is largely negligible.

To this end, a team of researchers from Tianjin University's School of Chemical Engineering and Technology created a unique n-TiO.2/BaTiO3/p-TiO2 A heterojunction that combines the piezoelectric effect with a pn junction to overcome the charge separation and transfer limitation of a pn junction.

“In our designed heterojunction, ferroelectric BaTiO3 layer is between n-TiO2 with oxygen vacancies and p-TiO2 with titanium vacancies,” shares Minhua Ai, lead author learning Published in KeAi magazine Green energy and environment. “Accordingly, TBT3 achieves a visible photocurrent density that is between 2.4 and 1.5 times that of TiO.2 and TiO2– BaTiO3 heterojunction, respectively.”

Notably, the stable polarized electric field induced by mechanical deformation generated in ferroelectric BaTiO3 can further tune the built-in electric fields based on the comprehensive characteristics of the charge carrier behavior in such a multi-heterojunction. and n-TiO2/BaTiO3/p-TiO2 The heterojunction achieves piezoelectrically enhanced PEC performance (2.84 times that of TiO2 at 1.23 V at RHE).

“Based on the piezoelectric effect and coupling to pn junctions, our work provides a piezoelectric polarization strategy to modulate the built-in electric field of the heterojunction to improve charge separation,” adds senior and corresponding author Lun Pen.





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Green energy and environment