The first perovskite found to be good at carrying photons, methylammonium lead tri-iodide
, degrades in air or moisture.
Antimony tri-iodide (Sb[I.sub.3]) is a compound semiconductor with an As[I.sub.3] -type crystal structure; it has been reported to be a potential semiconductor material for radiation detectors .
Hiratate, "Bismuth tri-iodide crystal for nuclear radiation detectors," IEEE Transactions on Nuclear Science, vol.
One proposed mechanism is an effect of the triiodine reaction that produces the tri-iodide
anion, sequestering oxidized iodine and finally decreasing organification .
Thus, it is critical to find new materials, which are well-appointed for replacing Pt that possesses good electroconductivity and electrocatalytic activity (ECA) toward the reduction of tri-iodide ions and cost-effective [1, 3].
Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to study the ECA and [R.sub.ct] of the CEs toward the reduction of tri-iodide to iodide.
As shown in Figure 2(d) the FESEM image of Ti[O.sub.2] reveals similar morphology as observed by  which is porous spherical nanoparticles that is important in the adsorption of the tri-iodide ion.
The peak in the range 0.75-1.5 V indicates the oxidation of iodide to tri-iodide (see (1)) and the peak in the range of -0.25 to 0.5 V indicates the reduction of tri-iodide to iodide (see (2)).
The total impedance ([Z.sub.S]) of the DSSC is given by the sum of the summation of impedance of diffusion and recombination in Ti[O.sub.2] photoanode ([Z.sub.T]), impedance at Pt electrode/electrolyte interface ([Z.sub.P]), and impedance of tri-iodide
diffusion in the electrolyte ([Z.sub.N]).
The iodide present in the electrolyte is capable of depassivating an oxide covered metal surface (in an analogous manner to chloride ions) the reducing tri-iodide providing a facile cathodic reaction to couple with anodic metal dissolution.
The reduction of the tri-iodide into iodide ions is characterised by a change in the electrolyte colour, yellow/brown to transparent, which in turn decreases the number of charge carrying species and leads to inferior device performance.
The metal is oxidised by the tri-iodide according to (2):