Effects of p-type-metal-doping (Ba, Cs, and Y) of the compact-TiO2 electron transporting layer on the photovoltaic properties of n-i-p perovskite solar cells

Tailoring of charge transport properties of the electron transport layer (ETL) in solution-processible solar cells is continuously addressed not only for the performance enhancements in perovskite solar cells but also in various other applications in nanotechnology. In this work, three p-type dopants: barium, cesium (Cs), and yttrium (Y) with varying crystal radii and charges are doped in the titanium dioxide (TiO2) material so as to modify the electrical and optical properties of the ETL. The pure and doped TiO2 films were prepared by spin-coating a sol–gel precursor and their effects on the crystal structure, morphology, optical, electrical and photovoltaic properties of the perovskite solar cells were studied and reported. Among them, Y-doped TiO2 with similar crystal radii as that of the host titanium atom showed an enhanced photo-conversion efficiency mainly contributed by enhanced open circuit voltage and fill factor. The power conversion efficiency (PCE) for the perovskite absorber layer on Cs- and Y-doped TiO2 show the maximum PCE of 2.81 and 4.50% respectively. These are encouraging results for optimizing the yttrium doping level and fabrication conditions to further push the performance indicators of PSCs

Chemical Vapor Deposited Mixed Metal Halide Perovskite Thin Films

In this article, we used a two-step chemical vapor deposition (CVD) method to synthesize methylammonium lead-tin triiodide perovskite films, MAPb1−xSnxI3, with x varying from 0 to 1. We successfully controlled the concentration of Sn in the perovskite films and used Rutherford backscattering spectroscopy (RBS) to quantify the composition of the precursor films for conversion into perovskite films. According to the RBS results, increasing the SnCl2 source amount in the reaction chamber translate into an increase in Sn concentration in the films. The crystal structure and the optical properties of perovskite films were examined by X-ray diffraction (XRD) and UV-Vis spectrometry. All the perovskite films depicted similar XRD patterns corresponding to a tetragonal structure with I4cm space group despite the precursor films having different crystal structures. The increasing concentration of Sn in the perovskite films linearly decreased the unit volume from about 988.4 Å3 for MAPbI3 to about 983.3 Å3 for MAPb0.39Sn0.61I3, which consequently influenced the optical properties of the films manifested by the decrease in energy bandgap (Eg) and an increase in the disorder in the band gap. The SEM micrographs depicted improvements in the grain size (0.3–1 µm) and surface coverage of the perovskite films compared with the precursor films