The effect of post-annealing treatment on the structural and optoelectronic properties of solution-processed TiO2 thin films

Electron and hole transporting layers are considered the key element of the fabrication of a high-performance photovoltaic device. An efficient electron transport layer (ETL) must provide better electrons extraction by minimizing the charge recombination rate. In the current work, we have successfully fabricated a solution-processed titanium dioxide (TiO2) thin film using a simple deposition technique to serve as an effective ETL for photovoltaic applications. The prepared TiO2 underwent different annealing processes during the deposition process to provide two sets of compact TiO2 (c-TiO2) thin films. The first set was annealed at a relatively low temperature (125 degrees C) and labeled as pristine TiO2, while the second set underwent an additional annealing process at 500 degrees C and labeled as post-annealed TiO2. The effect of post-annealing treatment on the structural and optoelectronic properties of the TiO2 layers was studied using FT-IR, XRD, SEM, UV-Vis absorption, and photoluminescence (PL) analysis. The post-annealed TiO2 thin film showed better crystallinity and larger grain sizes than the pristine TiO2. In addition, the optoelectronic investigations showed that the post-annealed TiO2 had lower band gap energy and higher photocatalytic activity, qualifying it to act as an effective ETL. Finally, the performance of the TiO2 electron transport layers was tested by fabricating two solar cell devices. It was found that the post-annealed TiO2 layer exhibits a better device performance than the pristine TiO2 by approximately a 21% increase in the power conversion efficiency (PCE).

Automated summary

In this study, a solution-processed titanium dioxide thin film was successfully fabricated as an effective electron transport layer (ETL) for photovoltaic applications. The post-annealed TiO2 showed improved crystallinity and larger grain sizes, with lower band gap energy and higher photocatalytic activity, making it a suitable ETL. The performance of the post-annealed TiO2 layer in solar cell devices exhibited approximately a 21% increase in power conversion efficiency (PCE) compared to the pristine TiO2 layer.