Modulations of photoinduced magnetoconductance for polymer diodes

Abstract

This study elucidates the magnetoconductance (MC) response of polymer diodes, which can be modulated by photoillumination, varying the composition of the active layer and applying electrical bias. Under illumination, the short-circuit current of polymer diodes with active layers of regioregular poly(3-hexylthiophene) (P3HT) exhibits an MC response of approximately −4.0% in a magnetic field B=1000mT at room temperature. The MC response drastically reverses from negative to positive (−23.0% to 2.0%) as the electrical bias is increased from nearly below to above the open-circuit voltage. However, it is quenched (<0.1%) when the illumination is turned off or an electron acceptor material, [6,6]-phenyl C61-butyric acid methyl ester, is blended with P3HT as the active layer, suggesting that, in nature, the MC response is associated with the illumination and excitonic states. The annihilation of triplet excitons probably dominates the negative MC response.

Role of electron-hole pair formation in organic magnetoresistance

“…However, detailed temperature, higher magnetic field, material and thickness dependent study of the MR line-shapes are needed to clarify the effect. This observation is in good agreement with Lee et al, who found similar behavior in light-induced MR response on P3HT/PCBM solar cells [14].…”

Carrier Dynamics in Pentacene|C60 Bilayer Solar Cell Investigated through the Magnetoconductance

“…The MC effect is defined as the ratio of the variation of the current density J induced by applying an external magnetic field B to the current density in the absence of B : MC = [ J ( B ) – J (0)] × 100/ J (0). It has been extensively investigated in organic solids, − and it has recently been reported that OSC devices without magnetic electrodes also exhibit the MC effect in both dark and light conditions. , Numerous mechanistic studies on various organic semiconductors have shown that the carrier dynamics of spin-carrying pairs following the spin conservation rule during collisions are crucial for the intrinsic MC effect. − Because an external magnetic field depresses the spin mixing in the spin-carrying pairs before the reaction, unless the magnetic field is higher than several tesla, , the product fraction of the spin-selective reaction changes with the field strength. The magnetic field dependence of the MC effect normally saturates in magnetic fields that are high in comparison with the internal magnetic field driving the spin mixing.…”

“…It has been extensively investigated in organic solids, 12−16 and it has recently been reported that OSC devices without magnetic electrodes also exhibit the MC effect in both dark and light conditions. 17,18 Numerous mechanistic studies on various organic semiconductors have shown that the carrier dynamics of spin-carrying pairs following the spin conservation rule during collisions are crucial for the intrinsic MC effect. 19−28 Because an external magnetic field depresses the spin mixing in the spin-carrying pairs before the reaction, unless the magnetic field is higher than several tesla, 24,29 the product fraction of the spin-selective reaction changes with the field strength.…”

Microscopic modeling of magnetic-field effects on charge transport in organic semiconductors

“…In the literature the high-field effect on the photocurrent, and even regular OMAR, is sometimes explained by these reactions of triplet excitons. 34,35 However, most of the calculations on triplet reactions in the literature are focused on single crystals. 13,33,36 We will use the stochastic Liouville equation to study the magnetic-field-dependence of triplet reactions in disordered organic semiconductors.…”