I have already attempted most of these questions; I just wantedsomeone else's opinion to see if my answers are right or wrong andtell me why if its wrong. Thanks:
Q1:
A doped semiconductor is dipped into a solution of electrolyte.The electrolyte solution contains a redox species with a mid-gapelectrode potential. After absorbing a photon in excess of itsbandgap energy, the photoexcited electron in the conduction band(CB) of a semiconductor moves spontaneously to the interfacebetween the semiconductor and the liquid electrolyte. The hole inthe valence band moves spontaneously away from the solid/liquidinterface and into the bulk of the semiconductor. What is thecorrect statement about the doping of this semiconductor?
a. n-doped, because there is an electric fieldgenerated at the interface that drives the electrons to thesolid/liquid interface.
b. n-doped, since it has an excess of electronsthe e- in the CB wants to escape.
c. p-doped, because it has an excess of negativecharges in the semiconductor at the solid/liquid interface thatattract the electrons.
d. p-doped, because there is an electric fieldthat drives the electrons to the solid/liquid interface
e. n-doped, because it has an excess of positivecharges in the semiconductor at the solid/liquid interface, whichattract the photoexcited electrons
Q2:
Calculate the maximum output voltage (a.k.a. cell potential) fora dye-sensitized solar cell constructed from n-type SnO2(ECB = EFermi = +0.3V) usingFe3+/Fe2+ as the redox mediator. Use AppendixD and assume that all concentrations are standard state.
Q3:
Which of the following is true about Graetzel-type solarcells?
a. Gratzel cells are not asefficient as multilayered dye-sensitized solar cells
b. Low surface area films of TiO2provide optimal binding for dyes
c. Cell voltages are susceptible torecombination from the CB to the redox mediator
d. Light absorption and cell output voltagesare worse than planar dye-sensitized solar cells
e. Band bending occurs in thesemiconductor phase
My answers are:
1. d
2. 0.47
3. e
I have already attempted most of these questions; I just wantedsomeone else's opinion to see if my answers are right or wrong andtell me why if its wrong. Thanks:
Q1:
A doped semiconductor is dipped into a solution of electrolyte.The electrolyte solution contains a redox species with a mid-gapelectrode potential. After absorbing a photon in excess of itsbandgap energy, the photoexcited electron in the conduction band(CB) of a semiconductor moves spontaneously to the interfacebetween the semiconductor and the liquid electrolyte. The hole inthe valence band moves spontaneously away from the solid/liquidinterface and into the bulk of the semiconductor. What is thecorrect statement about the doping of this semiconductor?
a. n-doped, because there is an electric fieldgenerated at the interface that drives the electrons to thesolid/liquid interface.
b. n-doped, since it has an excess of electronsthe e- in the CB wants to escape.
c. p-doped, because it has an excess of negativecharges in the semiconductor at the solid/liquid interface thatattract the electrons.
d. p-doped, because there is an electric fieldthat drives the electrons to the solid/liquid interface
e. n-doped, because it has an excess of positivecharges in the semiconductor at the solid/liquid interface, whichattract the photoexcited electrons
Q2:
Calculate the maximum output voltage (a.k.a. cell potential) fora dye-sensitized solar cell constructed from n-type SnO2(ECB = EFermi = +0.3V) usingFe3+/Fe2+ as the redox mediator. Use AppendixD and assume that all concentrations are standard state.
Q3:
Which of the following is true about Graetzel-type solarcells?
a. Gratzel cells are not asefficient as multilayered dye-sensitized solar cells
b. Low surface area films of TiO2provide optimal binding for dyes
c. Cell voltages are susceptible torecombination from the CB to the redox mediator
d. Light absorption and cell output voltagesare worse than planar dye-sensitized solar cells
e. Band bending occurs in thesemiconductor phase
My answers are:
1. d
2. 0.47
3. e
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