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Investigation of S-shaped current-voltage characteristics in high-performance solution-processed small molecule bulk heterojunction solar cells

Journal Article


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Abstract


  • The appearance of an S-shaped current-voltage curve and its impact on the performance of solution-processed small molecule p-DTS(FBTTh2)2:PC70BM bulk heterojunction solar cell devices were investigated. The power conversion efficiency of the devices showing S-curve characteristics was almost half of what was expected for this combination of materials, which was due to a low fill factor (FF) and 20% lower short circuit current density. A normal diode-like current-voltage curve was retrieved when the PCBM content of the active layer was increased, with power conversion efficiency reaching 6%. Analysis of the current-voltage characteristics of the S-curve solar cell devices showed that the effective voltage of the devices throughout the active layer was diminished due to an energy barrier. As a result, the charge collection efficiency was significantly affected. In addition, smaller external quantum efficiency (EQE) values in the absorption range of the small molecule donor in the S-curve devices suggested that charge generation was also affected. Recombination dynamics of both the normal and S-curve devices under steady-state conditions were quite similar. However, photovoltage decay results showed a distinguished pattern of recombination at open circuit conditions in the S-curve devices. This suggested different recombination rates at the cathode and anode electrodes, which is possibly due to the different composition of the donor-acceptor film near the contacts.

Publication Date


  • 2018

Citation


  • Aghassi, A., Fay, C. D. & Mozer, A. (2018). Investigation of S-shaped current-voltage characteristics in high-performance solution-processed small molecule bulk heterojunction solar cells. Organic Electronics: physics, materials, applications, 62 133-141.

Scopus Eid


  • 2-s2.0-85053146919

Ro Full-text Url


  • https://ro.uow.edu.au/cgi/viewcontent.cgi?article=4316&context=aiimpapers

Ro Metadata Url


  • http://ro.uow.edu.au/aiimpapers/3264

Has Global Citation Frequency


Number Of Pages


  • 8

Start Page


  • 133

End Page


  • 141

Volume


  • 62

Place Of Publication


  • Netherlands

Abstract


  • The appearance of an S-shaped current-voltage curve and its impact on the performance of solution-processed small molecule p-DTS(FBTTh2)2:PC70BM bulk heterojunction solar cell devices were investigated. The power conversion efficiency of the devices showing S-curve characteristics was almost half of what was expected for this combination of materials, which was due to a low fill factor (FF) and 20% lower short circuit current density. A normal diode-like current-voltage curve was retrieved when the PCBM content of the active layer was increased, with power conversion efficiency reaching 6%. Analysis of the current-voltage characteristics of the S-curve solar cell devices showed that the effective voltage of the devices throughout the active layer was diminished due to an energy barrier. As a result, the charge collection efficiency was significantly affected. In addition, smaller external quantum efficiency (EQE) values in the absorption range of the small molecule donor in the S-curve devices suggested that charge generation was also affected. Recombination dynamics of both the normal and S-curve devices under steady-state conditions were quite similar. However, photovoltage decay results showed a distinguished pattern of recombination at open circuit conditions in the S-curve devices. This suggested different recombination rates at the cathode and anode electrodes, which is possibly due to the different composition of the donor-acceptor film near the contacts.

Publication Date


  • 2018

Citation


  • Aghassi, A., Fay, C. D. & Mozer, A. (2018). Investigation of S-shaped current-voltage characteristics in high-performance solution-processed small molecule bulk heterojunction solar cells. Organic Electronics: physics, materials, applications, 62 133-141.

Scopus Eid


  • 2-s2.0-85053146919

Ro Full-text Url


  • https://ro.uow.edu.au/cgi/viewcontent.cgi?article=4316&context=aiimpapers

Ro Metadata Url


  • http://ro.uow.edu.au/aiimpapers/3264

Has Global Citation Frequency


Number Of Pages


  • 8

Start Page


  • 133

End Page


  • 141

Volume


  • 62

Place Of Publication


  • Netherlands