Ultrafast long-range spin-funneling in solution-processed Ruddlesden-Popper halide perovskites

Room-temperature spin-based electronics is the vision of spintronics. Presently, there are few suitable material systems. Herein, we reveal that solution-processed mixed-phase Ruddlesden-Popper perovskite thin-films transcend the challenges of phonon momentum-scattering that limits spin-transfer in conventional semiconductors. This highly disordered system exhibits a remarkable efficient ultrafast funneling of photoexcited spin-polarized excitons from two-dimensional (2D) to three-dimensional (3D) phases at room temperature. We attribute this efficient exciton relaxation pathway towards the lower energy states to originate from the energy transfer mediated by intermediate states. This process bypasses the omnipresent phonon momentum-scattering in typical semiconductors with stringent band dispersion, which causes the loss of spin information during thermalization. Film engineering using graded 2D/3D perovskites allows unidirectional out-of-plane spin-funneling over a thickness of similar to 600 nm. Our findings reveal an intriguing family of solution-processed perovskites with extraordinary spin-preserving energy transport properties that could reinvigorate the concepts of spin-information transfer.
Funding Agencies|Nanyang Technological University [M4080514, M4081293]; Ministry of Education [RG104/16, RG173/16, MOE2015-T2-2-015, MOE2016-T2-1-034, MOE2017-T2-1-001]; NTU-A*STAR Silicon Technologies Center of Excellence Program Grant [11235100003]; US Office of Naval Research [ONRGNICOP-N62909-17-1-2155]; Singapore National Research Foundation [NRF-CRP14-2014-03, NRF2018-ITC001-001, NRF-NRFI-2018-04]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [200900971]; European Commission [717026]; Joint NTU-LiU PhD programme on Materials and Nanoscience