Correlation between magneto-photocurrent and power conversion efficiency in organic solar cells

In order to investigate the effect of spin 1/2 radical on the photocurrent in organic solar cells, we studied magneto-photocurrent (MPC) and power conversion efficiency (PCE) of ``standard'' P3HT:PCBM (1.2:1) device at various Galvinoxyl radical wt{\%}. The MPC measurements were performed to understand the increase in $J$sc and hence PCE of the OPV device with Galvinoxyl wt{\%}. We found that the MPC reduction with Galvinoxyl wt{\%} follows the same trend as that of the PCE enhancement. We propose that MPC in OPV blends is due to spin-mixing mechanism related with the manifold of the charge transfer (CT) state at the donor-acceptor interfaces. Our results thus demonstrate that the Galvinoxyl spin 1/2 radical additives act as spin flip initiator within this exciton manifold. This process is unraveled via MPC of the doped devices. Supported by the NSF-MRSEC program at the UoU.