We demonstrate enhanced organic photovoltaic cell (OPV) efficiency through the use of continuously graded donoracceptor (DA) heterojunctions. Device performance is a strong function of both DA grading and overall composition ratio. The use of a tunable gradient permits an increase in the DA interface area for high-exciton diffusion efficiency relative to a planar heterojunction, while also improving the charge collection efficiency relative to a uniform mixture. Using the archetypical DA pair of copper phthalocyanine and C 60, a power conversion efficiency of ηP = (2.1 \pm 0.1) is realized under 100 mW/cm2 simulated AM1.5G solar illumination for a graded heterojunction. This represents an improvement in ηP of 60 relative to a planar heterojunction OPV and 20 compared to a uniformly mixed heterojunction OPV.
|Original language||English (US)|
|Number of pages||7|
|Journal||IEEE Journal on Selected Topics in Quantum Electronics|
|State||Published - Nov 2010|
Bibliographical noteFunding Information:
Manuscript received February 3, 2010; revised April 1, 2010; accepted April 19, 2010. Date of publication June 21, 2010; date of current version December 3, 2010. This work was supported in part by the National Science Foundation (NSF) under Award CBET-0946723 and in part by the NSF Materials Research Science and Engineering Centers Program under Awards DMR-0212302 and DMR-0819885. The work of R. J. Holmes was supported in part by 3M Company under a Non-Tenured Faculty Grant.
- molecular electronics
- organic compounds
- photovoltaic cells
- semiconductor heterojunctions