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ZnO@SnO2 engineered composite photoanodes for dye sensitized solar cells.

Milan R, Selopal GS, Epifani M, Natile MM, Sberveglieri G, Vomiero A, Concina I - Sci Rep (2015)

Bottom Line: Bi-oxide photoanodes performed much better in terms of photoconversion efficiency (PCE) (4.96%) compared to bare SnO2 (1.20%) and ZnO (1.03%).Synergistic cooperation is effective for both open circuit voltage and photocurrent density: enhanced values were indeed recorded for the layered photoanode as compared with bare oxides (Voc enhanced from 0.39 V in case of bare SnO2 to 0.60 V and Jsc improved from 2.58 mA/cm(2) pertaining to single ZnO to 14.8 mA/cm(2)).Compared with previously reported results, this study testifies how a simple electrode design is powerful in enhancing the functional performances of the final device.

View Article: PubMed Central - PubMed

Affiliation: Department of Information Engineering, University of Brescia - via Valotti 9, 25133 Brescia, Italy.

ABSTRACT
Layered multi-oxide concept was applied for fabrication of photoanodes for dye-sensitized solar cells based on ZnO and SnO2, capitalizing on the beneficial properties of each oxide. The effect of different combinations of ZnO@SnO2 layers was investigated, aimed at exploiting the high carrier mobility provided by the ZnO and the higher stability under UV irradiation pledged by SnO2. Bi-oxide photoanodes performed much better in terms of photoconversion efficiency (PCE) (4.96%) compared to bare SnO2 (1.20%) and ZnO (1.03%). Synergistic cooperation is effective for both open circuit voltage and photocurrent density: enhanced values were indeed recorded for the layered photoanode as compared with bare oxides (Voc enhanced from 0.39 V in case of bare SnO2 to 0.60 V and Jsc improved from 2.58 mA/cm(2) pertaining to single ZnO to 14.8 mA/cm(2)). Improved functional performances of the layered network were ascribable to the optimization of both high chemical capacitance (provided by the SnO2) and low recombination resistance (guaranteed by ZnO) and inhibition of back electron transfer from the SnO2 conduction band to the oxidized species of the electrolyte. Compared with previously reported results, this study testifies how a simple electrode design is powerful in enhancing the functional performances of the final device.

No MeSH data available.


Proposed band energy scheme and main charge transport processes for (a) hemi core-shell ZnO-SnO2 structures and (c) layered architecture proposed in this work. (b) and (d) show the two configurations theoretically corresponding to band energy diagrams reported in (a) and (c), respectively (blue spheres: SnO2; orange structures: ZnO; yellow spheres: dye N719).
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f3: Proposed band energy scheme and main charge transport processes for (a) hemi core-shell ZnO-SnO2 structures and (c) layered architecture proposed in this work. (b) and (d) show the two configurations theoretically corresponding to band energy diagrams reported in (a) and (c), respectively (blue spheres: SnO2; orange structures: ZnO; yellow spheres: dye N719).

Mentions: It should be indeed pointed out that several Authors claimed for an overall band alignment effect induced by the addition of ZnO to SnO2 in photoanode composition. This hypothesis deserves to be discussed, since it has been broadly debated in previous literature on the topic. As mentioned above, the first work exploring the properties of mixed ZnO/SnO2 photoanodes20 hypothesized that an effect of band gap engineering might be induced by surrounding the SnO2 particles with ZnO species, favoring the charge injection from the N719 LUMO to the ZnO CB and then transferring the photogenerated electrons to the SnO2 CB. This favorable band alignment would result in two relevant improvements, as schematically illustrated in Fig. 3a: the first advantage would be the possibility to properly inject photogenerated electrons from N719 to SnO2 through the ZnO (which however still presents issues as for injection in itself) and the second relevant advantage would be the elimination of the so-called back recombination between SnO2 CB and the electrolyte redox couple (represented by the dashed grey arrow in Fig. 3a), as the outer ZnO shell acts as effective tunneling barrier between the SnO2 NP and the electrolyte.


ZnO@SnO2 engineered composite photoanodes for dye sensitized solar cells.

Milan R, Selopal GS, Epifani M, Natile MM, Sberveglieri G, Vomiero A, Concina I - Sci Rep (2015)

Proposed band energy scheme and main charge transport processes for (a) hemi core-shell ZnO-SnO2 structures and (c) layered architecture proposed in this work. (b) and (d) show the two configurations theoretically corresponding to band energy diagrams reported in (a) and (c), respectively (blue spheres: SnO2; orange structures: ZnO; yellow spheres: dye N719).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4588567&req=5

f3: Proposed band energy scheme and main charge transport processes for (a) hemi core-shell ZnO-SnO2 structures and (c) layered architecture proposed in this work. (b) and (d) show the two configurations theoretically corresponding to band energy diagrams reported in (a) and (c), respectively (blue spheres: SnO2; orange structures: ZnO; yellow spheres: dye N719).
Mentions: It should be indeed pointed out that several Authors claimed for an overall band alignment effect induced by the addition of ZnO to SnO2 in photoanode composition. This hypothesis deserves to be discussed, since it has been broadly debated in previous literature on the topic. As mentioned above, the first work exploring the properties of mixed ZnO/SnO2 photoanodes20 hypothesized that an effect of band gap engineering might be induced by surrounding the SnO2 particles with ZnO species, favoring the charge injection from the N719 LUMO to the ZnO CB and then transferring the photogenerated electrons to the SnO2 CB. This favorable band alignment would result in two relevant improvements, as schematically illustrated in Fig. 3a: the first advantage would be the possibility to properly inject photogenerated electrons from N719 to SnO2 through the ZnO (which however still presents issues as for injection in itself) and the second relevant advantage would be the elimination of the so-called back recombination between SnO2 CB and the electrolyte redox couple (represented by the dashed grey arrow in Fig. 3a), as the outer ZnO shell acts as effective tunneling barrier between the SnO2 NP and the electrolyte.

Bottom Line: Bi-oxide photoanodes performed much better in terms of photoconversion efficiency (PCE) (4.96%) compared to bare SnO2 (1.20%) and ZnO (1.03%).Synergistic cooperation is effective for both open circuit voltage and photocurrent density: enhanced values were indeed recorded for the layered photoanode as compared with bare oxides (Voc enhanced from 0.39 V in case of bare SnO2 to 0.60 V and Jsc improved from 2.58 mA/cm(2) pertaining to single ZnO to 14.8 mA/cm(2)).Compared with previously reported results, this study testifies how a simple electrode design is powerful in enhancing the functional performances of the final device.

View Article: PubMed Central - PubMed

Affiliation: Department of Information Engineering, University of Brescia - via Valotti 9, 25133 Brescia, Italy.

ABSTRACT
Layered multi-oxide concept was applied for fabrication of photoanodes for dye-sensitized solar cells based on ZnO and SnO2, capitalizing on the beneficial properties of each oxide. The effect of different combinations of ZnO@SnO2 layers was investigated, aimed at exploiting the high carrier mobility provided by the ZnO and the higher stability under UV irradiation pledged by SnO2. Bi-oxide photoanodes performed much better in terms of photoconversion efficiency (PCE) (4.96%) compared to bare SnO2 (1.20%) and ZnO (1.03%). Synergistic cooperation is effective for both open circuit voltage and photocurrent density: enhanced values were indeed recorded for the layered photoanode as compared with bare oxides (Voc enhanced from 0.39 V in case of bare SnO2 to 0.60 V and Jsc improved from 2.58 mA/cm(2) pertaining to single ZnO to 14.8 mA/cm(2)). Improved functional performances of the layered network were ascribable to the optimization of both high chemical capacitance (provided by the SnO2) and low recombination resistance (guaranteed by ZnO) and inhibition of back electron transfer from the SnO2 conduction band to the oxidized species of the electrolyte. Compared with previously reported results, this study testifies how a simple electrode design is powerful in enhancing the functional performances of the final device.

No MeSH data available.