Fabrication and Characterization of Diphenylhexatriene-Based Quasi-Two-Dimensional Perovskites for Potential Singlet Fission Capable Photovoltaics.

Current generation single-junction photovoltaic cells are limited by thermalization and carrier cooling of hot charge carriers. A strategy with the potential to circumvent this efficiency limit is to utilize singlet fission to create pairs of exciton states from a single photon. Utilizing singlet fission for photovoltaic improvement requires coupling a singlet fission chromophore with a suitable semiconductor in such a way to allow for efficient triplet energy transfer from the chromophore to the semiconductor. So far, this has proven to be elusive. While many efforts to develop a singlet fission sensitized photovoltaic have focused on the coupling between the singlet fission-capable chromophore tetracene and the semiconductors silicon or lead sulfide, very few have looked into the potential of coupling singlet fission capable chromophores with metal halide perovskites, a class of semiconductors that are set to form the basis of the next generation of PV devices. In this letter we describe our investigation into the fabrication and study of a novel quasi-two-dimensional perovskite which utilizes an amine functionalized derivative of the singlet fission capable chromophore, diphenylhexatriene (2,2'-(((1E,3E,5E)-hexa-1,3,5-triene-1,6,diyl)bis(4,1,-phenylene))bis(ethan-1-aminium) diiodide). Though we observed that the addition of the chromophore significantly influenced the morphology of the film and in turn reduced the photoluminescence quantum efficiency and photoluminescence lifetime of the MASn0.5Pb0.5I3 perovskite, prototype photovoltaic devices still showed non-zero photocurrent and a relative increase in the external quantum efficiency, which correlates with the absorption range of the singlet fission capable chromophore. The involvment of singlet fission in this result was further confirmed via magnetic photolumincene measrments. This study demonstrates the potential for singlet fission two-dimensional perovskite systems as a way forward to mitigate high energy photon losses in PV cells.