Simple Analytic Description of Collection Efficiency in Organic Photovoltaics.
The collection of charge carriers is a fundamental step in the photovoltaic conversion process. In disordered organic films, low mobility and disorder can make collection the performance-limiting step in energy conversion. We derive two analytic relationships for carrier collection efficiency in organic photovoltaics that account for the presence or absence of carrier-selective electrodes. These equations directly include drift and diffusive carrier transport in the device active layers and account for possible losses from Langevin and Shockley-Read-Hall recombination mechanisms. General relationships among carrier mobility, contact selectivity, recombination processes, and organic photovoltaic figures of merit are established. Our results suggest that device collection efficiency remains mobility-limited for many materials systems, and a renewed emphasis should be placed on materials' purity.
Argonne-Northwestern Solar Energy Research Center, Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60201, United States.
Brett M
BM
Savoie
Argonne-Northwestern Solar Energy Research Center, Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60201, United States.
Bijan
B
Movaghar
Argonne-Northwestern Solar Energy Research Center, Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60201, United States.
Tobin J
TJ
Marks
Argonne-Northwestern Solar Energy Research Center, Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60201, United States.
Mark A
MA
Ratner
energy conversion; organic photovolatics; transport in disordered materials