Distinguishing Spin Relaxation Mechanisms in Organic Semiconductors

Abstract

A theory is introduced for spin relaxation and spin diffusion of hopping carriers in a disordered system. For disorder described by a distribution of waiting times between hops (e.g., from multiple traps, site-energy disorder, and/or positional disorder) the dominant spin relaxation mechanisms in organic semiconductors (hyperfine, hopping-induced spin-orbit, and intrasite spin relaxation) each produce different characteristic spin relaxation and spin diffusion dependences on temperature. The resulting unique experimental signatures predicted by the theory for each mechanism in organic semiconductors provide a prescription for determining the dominant spin relaxation mechanism.

Exchange-Driven Spin Relaxation in Ferromagnet-Oxide-Semiconductor Heterostructures

“…These randomly located polarized nuclei in turn give rise to an inhomogeneous nuclear field distribution that leads to the dephasing of itinerant photoexcited carriers that move across those donor sites. The spin relaxation via path 1 can be calculated using a theory of continuous-time-random-walk for spin [32,33]. As was recently shown in Ref.…”

Recent progress in organic spintronics

“…Recently, several theoretical works have also addressed the role of SOI in relation to spin relaxation for (single carrier) hopping in organic semiconductors [3,4,13,14]. These studies suggest that SOI is indeed important for spin relaxation during polaron hops in certain organic semiconductors, in particular for tris-(8-hydroxyquinoline)aluminum (Alq 3 ), an extensively studied material in organic spintronics.…”

“…On the other hand, recent reports by Rybicki et al on SOI in conjugated polymer chains suggest that it is negligible in those systems [15,16]. As has been suggested by Harmon et al, further investigation of organic semiconductors with systematic variation of (1) elemental substitution (to obtain different SOI), (2) hopping rates (via temperature or molecular order/disorder) and (3) hyperfine fields (using deuteration) should be performed to shed light on the importance of SOI [13].…”

Polaron spin echo envelope modulations in an organic semiconducting polymer

“…This is equivalent to the strong collision approximation which provides a simple way of describing the spin relaxation of a randomly hopping carrier. 42 The multiple trapping model [43][44][45][46] is an implementation of the strong collision approximation, often used to explain the transport in organic materials 47 and particularly in PPV and its derivatives. 48 We base our consideration on the multiple trapping model.…”