Photovoltaic properties of perovskite solar cells according to TiO₂ particle size

The photovoltaic properties of TiO₂ used for the electron transport layer in perovskite solar cells(PSCs) are compared according to the particle size. The PSCs are fabricated and prepared by employing 20 nm and 30 nm TiO₂ as well as a 1:1 mixture of these particles. To analyze the microstructure and pores of each TiO₂ layer, a field emission scanning electron microscope and the Brunauer-Emmett-Teller(BET) method are used. The absorbance and photovoltaic characteristic of the PSC device are examined over time using ultraviolet-visible-near-infrared spectroscopy and a solar simulator. The microstructural analysis shows that the TiO₂ shape and layer thicknesses are all similar, and the BET analysis results demonstrate that the size of TiO₂ and in surface pore size is very small. The results of the photovoltaic characterization show that the mean absorbance is similar, in a range of about 400-800 nm. However, the device employing 30 nm TiO₂ demonstrates the highest energy conversion efficiency(ECE) of 15.07 %. Furthermore, it is determined that all the ECEs decrease over time for the devices employing the respective types of TiO₂. Such differences in ECE based on particle size are due to differences in fill factor, which changes because of changes in interfacial resistance during electron movement owing to differences in the TiO₂ particle size, which is explained by a one-dimensional model of the electron path through various TiO₂ particles.