17.1%-Efficiency organic photovoltaic cell enabled with two higher-LUMO-level acceptor guests as the quaternary strategy

Quaternary blended organic solar cells utilize four blended material components (one donor plus three acceptors, two donors and two acceptors, or three donors plus one acceptor) as the active layer materials. The use of four material components allows us to have more material selections and more mechanism choices to improve the photon-to-electron conversion efficiency. In this contribution, we present a new case of quaternary material system, that shows 17.1% efficiency obtained by adding IDIC and PC71BM as the guest acceptors of the host binary of PM6:Y6. The lowest unoccupied molecular orbital (LUMO) levels of IDIC and PC71BM are both higher than that of Y6, which is one reason to obtain increased open-circuit voltage (V-oc) in the quaternary device. Upon introduction of IDIC and PC71BM as the acceptor guests, the hole and electron mobilities are both increased, which contributes to the increased short-circuit current-density (J(sc)). Effects of the weight ratios of the three acceptor components are investigated, which demonstrates that the increased hole and electron mobilities, the accelerated hole-transfer, and the reduced monomolecular recombination are the factors contributing to the increased J(sc) and fill-factor. This case of quaternary device demonstrates the applicability of the quaternary strategy in increasing the device functions and hence the efficiencies in the field of organic photovoltaic cells.