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Hybrid graphene-metal oxide solution processed electron transport layers for large area high-performance organic photovoltaics.

Beliatis MJ, Gandhi KK, Rozanski LJ, Rhodes R, McCafferty L, Alenezi MR, Alshammari AS, Mills CA, Jayawardena KD, Henley SJ, Silva SR - Adv. Mater. Weinheim (2014)

Bottom Line: Solution processed core-shell nano-structures of metal oxide-reduced graphene oxide (RGO) are used as improved electron transport layers (ETL), leading to an enhancement in photocurrent charge transport in PCDTBT:PC70 BM for both single cell and module photovoltaic devices.As a result, the power conversion efficiency for the devices with RGO-metal oxides for ETL increases 8% in single cells and 20% in module devices.

View Article: PubMed Central - PubMed

Affiliation: Advanced Technology Institute, University of Surrey, Guildford, GU2 7XH, UK.

No MeSH data available.


AFM micrographs of the morphologies of different ETL materials on top of the photoactive layer a) TiO2, b) TiO2 – RGO, c) ZnO, d) ZnO-RGO and e) the absorption spectra of those stratified devices before Al back electrode deposition.
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fig03: AFM micrographs of the morphologies of different ETL materials on top of the photoactive layer a) TiO2, b) TiO2 – RGO, c) ZnO, d) ZnO-RGO and e) the absorption spectra of those stratified devices before Al back electrode deposition.

Mentions: To obtain additional insight into the device performance, we examined the morphology of the metal oxide derived films. Atomic Force Microscopy (AFM) was used to examine the MO films on top of the active layer, before the back electrode deposition, in order to obtain the topographies shown in Figure3. Uniform films with all ETL materials composed of MO nanoparticles are observed. For pristine MO films cast from as-diluted solutions (as described in materials synthesis), the root mean square (RMS) roughness and maximum height were 0.7 nm, 4.2 nm for TiO2, while for ZnO these values were 0.59 nm and 3.38 nm. For the RGO-loaded MO films the equivalent values are 0.82 nm, 4.93 nm for RGO-TiO2 and 0.63 nm, 3.74 nm for RGO-ZnO. Although the films made with the commercial MO nanoparticle powders are similar in roughness to those films derived from sol-gel based precursors in other studies,20 intriguingly the commercial MO powders used here exhibit enhanced performance. This is ascribed to better crystallinity of the MO nanoparticle powder compared to the precursor, which contributes to improved charge extraction. Films made with TiO2 composites show a higher roughness compared to those of ZnO, as shown in Figure 3, a known factor which affects the performance of devices. It can be seen that the ETLs made with the hybrid graphene-MO materials are rougher to that ETLs using pristine MO. However, loading of RGO improves the conductivity of the film, evidenced by the decreased series resistance (Rs) observed in the single cell devices (Table1). This decrease in Rs leads to ∼8% improvement in the efficiency of devices with hybrid ETLs. The absorption spectra of different ETLs within devices of the same architecture are shown in Figure 3e. The absorption spectra are very similar for all devices indicating there is minimum absorption from the ETLs; this suggests that it does not interfere with the ETL's secondary function as an optical spacer.4,21 As a result, the enhanced efficiencies observed with the RGO-MO hybrid ETLs can be ascribed primarily to their improved electrical characteristics.


Hybrid graphene-metal oxide solution processed electron transport layers for large area high-performance organic photovoltaics.

Beliatis MJ, Gandhi KK, Rozanski LJ, Rhodes R, McCafferty L, Alenezi MR, Alshammari AS, Mills CA, Jayawardena KD, Henley SJ, Silva SR - Adv. Mater. Weinheim (2014)

AFM micrographs of the morphologies of different ETL materials on top of the photoactive layer a) TiO2, b) TiO2 – RGO, c) ZnO, d) ZnO-RGO and e) the absorption spectra of those stratified devices before Al back electrode deposition.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4286003&req=5

fig03: AFM micrographs of the morphologies of different ETL materials on top of the photoactive layer a) TiO2, b) TiO2 – RGO, c) ZnO, d) ZnO-RGO and e) the absorption spectra of those stratified devices before Al back electrode deposition.
Mentions: To obtain additional insight into the device performance, we examined the morphology of the metal oxide derived films. Atomic Force Microscopy (AFM) was used to examine the MO films on top of the active layer, before the back electrode deposition, in order to obtain the topographies shown in Figure3. Uniform films with all ETL materials composed of MO nanoparticles are observed. For pristine MO films cast from as-diluted solutions (as described in materials synthesis), the root mean square (RMS) roughness and maximum height were 0.7 nm, 4.2 nm for TiO2, while for ZnO these values were 0.59 nm and 3.38 nm. For the RGO-loaded MO films the equivalent values are 0.82 nm, 4.93 nm for RGO-TiO2 and 0.63 nm, 3.74 nm for RGO-ZnO. Although the films made with the commercial MO nanoparticle powders are similar in roughness to those films derived from sol-gel based precursors in other studies,20 intriguingly the commercial MO powders used here exhibit enhanced performance. This is ascribed to better crystallinity of the MO nanoparticle powder compared to the precursor, which contributes to improved charge extraction. Films made with TiO2 composites show a higher roughness compared to those of ZnO, as shown in Figure 3, a known factor which affects the performance of devices. It can be seen that the ETLs made with the hybrid graphene-MO materials are rougher to that ETLs using pristine MO. However, loading of RGO improves the conductivity of the film, evidenced by the decreased series resistance (Rs) observed in the single cell devices (Table1). This decrease in Rs leads to ∼8% improvement in the efficiency of devices with hybrid ETLs. The absorption spectra of different ETLs within devices of the same architecture are shown in Figure 3e. The absorption spectra are very similar for all devices indicating there is minimum absorption from the ETLs; this suggests that it does not interfere with the ETL's secondary function as an optical spacer.4,21 As a result, the enhanced efficiencies observed with the RGO-MO hybrid ETLs can be ascribed primarily to their improved electrical characteristics.

Bottom Line: Solution processed core-shell nano-structures of metal oxide-reduced graphene oxide (RGO) are used as improved electron transport layers (ETL), leading to an enhancement in photocurrent charge transport in PCDTBT:PC70 BM for both single cell and module photovoltaic devices.As a result, the power conversion efficiency for the devices with RGO-metal oxides for ETL increases 8% in single cells and 20% in module devices.

View Article: PubMed Central - PubMed

Affiliation: Advanced Technology Institute, University of Surrey, Guildford, GU2 7XH, UK.

No MeSH data available.