Microstructural Control of Charge Generation in Organic Solar Cells
Event details
| Date | 11.12.2014 |
| Hour | 16:30 › 17:30 |
| Speaker | Prof. Natali Banerji, University of Fribourg |
| Location | |
| Category | Conferences - Seminars |
In organic solar cells, excitons are dissociated by charge separation between an electron donor (e.g. conjugated polymer) and an electron acceptor (e.g. fullerene derivative). For solid-state blends of the two components, their precise arrangement into a bulk heterojunction (BHJ) plays an important role, and this microstructure was recently revealed to be very complex. Not only can the polymer and fullerene arrange into either amorphous or crystalline neat domains of variable size, but an additional intimately mixed polymer-fullerene phase has been identified.
We show here that microstructure and photophysical properties in polymer:fullerene blends go hand-in-hand to determine the efficiency of organic solar cells. Ultrafast transient absorption, electro-absorption and fluorescence up-conversion spectroscopy were used to investigate the dynamics of charge separation in samples with well-characterized microstructures. Blends of the pBTTT and PBDTTPD polymers with PCBM gave us access to different scenarios, such as a single intimately mixed polymer:fullerene phase, an intermixed phase with additional pure PCBM clusters, or a three-phase microstructure of pure polymer aggregates, pure fullerene clusters and intermixed regions.
Moreover, we have selectively excited either the fullerene or the polymer in order to evaluate the effect of microstructure on both the electron and hole transfer pathways. We discuss how an ideal microstructure can promote generation of free charge carriers and relate the high photovoltaic performance of the PBDTTPD blend (up to 8.5 %) to its favorable properties in terms of microstructure and exciton delocalization.
Bio: Prof. Natalie Banerji joined the University of Fribourg, Switzerland, as an Associate Professor in September 2014. Previously (2011-2014), she held an autonomously funded project-leader position (SNSF Ambizione Fellowship) at EPFL. Between 2009 and 2011, she was a SNSF post-doctoral fellow in the group of Professor Alan J. Heeger at the University of California, Santa Barbara. She obtained her Ph. D. degree in Chemistry at the University of Geneva, Switzerland, in 2009. Her research interests include ultrafast spectroscopy and photophysics of organic electronic materials
We show here that microstructure and photophysical properties in polymer:fullerene blends go hand-in-hand to determine the efficiency of organic solar cells. Ultrafast transient absorption, electro-absorption and fluorescence up-conversion spectroscopy were used to investigate the dynamics of charge separation in samples with well-characterized microstructures. Blends of the pBTTT and PBDTTPD polymers with PCBM gave us access to different scenarios, such as a single intimately mixed polymer:fullerene phase, an intermixed phase with additional pure PCBM clusters, or a three-phase microstructure of pure polymer aggregates, pure fullerene clusters and intermixed regions.
Moreover, we have selectively excited either the fullerene or the polymer in order to evaluate the effect of microstructure on both the electron and hole transfer pathways. We discuss how an ideal microstructure can promote generation of free charge carriers and relate the high photovoltaic performance of the PBDTTPD blend (up to 8.5 %) to its favorable properties in terms of microstructure and exciton delocalization.
Bio: Prof. Natalie Banerji joined the University of Fribourg, Switzerland, as an Associate Professor in September 2014. Previously (2011-2014), she held an autonomously funded project-leader position (SNSF Ambizione Fellowship) at EPFL. Between 2009 and 2011, she was a SNSF post-doctoral fellow in the group of Professor Alan J. Heeger at the University of California, Santa Barbara. She obtained her Ph. D. degree in Chemistry at the University of Geneva, Switzerland, in 2009. Her research interests include ultrafast spectroscopy and photophysics of organic electronic materials
Practical information
- General public
- Free
Organizer
- Dr Frank van Mourik