Use of lateral structures to monitor and evaluate degradation of key photovoltaic parameters in an organic bulk heterojunction material
Abstract
Charge transport and recombination mechanisms within organic bulk heterojunction (BHJ) systems have been studied using lateral devices to perform in situ potentiometry. We have developed a simplified measurement technique using two types of lateral structures to elicit key charge transport parameters and study the time and process dependence of the carrier mobilities and their ratio. Small geometry lateral devices are used to evaluate the mobility of the slower carrier within the P3HT:PCBM material system. Larger structures with 5 in situ voltage probes are used to construct a simple potential profile of the device channel and accurately determine the carrier mobility ratio. These two measurements enable the calculation of carrier densities and the recombination coefficient. We monitor the change in these parameters as the P3HT:PCBM film degrades in the presence of oxygen and also examine the effect of the solvent additive 1,8-diiodooctane on this degradation mechanism. By exposing ethanol vapor to the BHJ film, we induce traps in the material and monitor the shift in dominant nongeminate recombination mechanism to a more unimolecular type. We are also able to measure the resulting decrease in carrier mobilities due to the presence of dipole-induced traps. Lateral devices are useful material diagnostic structures for studying degradation in BHJ materials.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Dec 03, 2014
- Source ID
- 10.1063/1.4903222
Entities
People
- Ananth Dodabalapur
- Eric Danielson
- Zi-en Ooi
Organizations
- Agency for Science, Technology and Research
- Institute of Materials Research and Engineering
- Office of Naval Research
- University of Texas at Austin