The identification of recombination centers in organic solar cells

Abstract

Recombination in bulk heterojunction organic solar cells is explored by observing the result of prolonged white light illumination and thermal annealing. The photocurrent spectral response, the steady state photocurrent-voltage characteristics and transient photoconductivity measurements on PCDTBT:PCBM and P3HT:PCBM solar cells provide information about recombination centers. Illumination generates deep traps while thermal annealing broadens the band tail localized states. Both types of state act as recombination centers. The evidence suggests that hydrogen abstraction, migration and re-bonding is responsible for the creation and recovery of recombination centers.