Spin-dependent recombination of photoinduced carriers in phthalocyanine/C60heterojunctions

Abstract

Spin-dependent recombination of photoinduced carriers in H 2 -phthalocyanine (H 2 Pc͒/C 60 heterojunctions is studied by electrically detected electron-spin resonance ͑EDESR͒ spectroscopy. The EDESR spectrum of the H 2 Pc/C 60 consists of two components A and B, the g values of which are 2.0018Ϯ0.0002 and 2.0010Ϯ0.0002, respectively. The two components are attributed to exchange-coupled localized electron-hole pairs trapped at different types of recombination centers. Component A has spin-flip satellites due to an interaction between the electron ͑or hole͒ spin, and its surrounding nuclear spins of protons which belong to the H 2 Pc rings. From the satellite intensity, the distance between the electron ͑or hole͒ and the protons is estimated to be 4.33Ϯ0.25 Å, indicating that the localized pairs for the component A locate close to the H 2 Pc rings. The spin dynamics of the localized pairs for the component A is studied by a microwave recovery experiment, in which the time dependence of the EDESR signal intensity is measured after turning the resonant microwave on and off. A theoretical model of the spin-dependent recombination of the exchange-coupled electron-hole pair is proposed with which the experimental results of the microwave recovery are explained. By a theoretical analysis, it is found that Rտ1ϫ10 6 s Ϫ1 and DϩW sl ϭ6.2 (Ϯ0.8)ϫ10 4 s Ϫ1 for component A at room temperature, where R is the recombination rate of the localized pair in the S z ϭ0 triplet sublevel, and D and W sl are the dissociation and the spin-lattice relaxation rates, respectively, of the pairs in the triplet sublevels. The photocurrent I 2 that is caused by the dissociation of the localized pairs for component A is about 5% of the total photocurrent.

Electrically detected and conventional magnetic resonance investigation of surface and bulk states in polyaniline thin films

“…In fact, over the past years it has provided valuable insight into various transport and recombination processes in semiconductors. [6][7][8][9][10][11] In this work we have used EDMR and EPR to investigate emeraldine base polyaniline films. We observed a transition of the magnetic susceptibility dependence on temperature, from a linear decrease with increasing temperature ͑localized Curie spins͒ to a constant value ͑delocalized Pauli spins͒.…”

Modulation frequency dependence of continuous-wave optically/electrically detected magnetic resonance

“…Because cwODMR and cwEDMR can be used to distinguish overlapping recombination bands and their dynamics in disordered materials, they have also been used to investigate (usually amorphous) organic semiconductors: cwODMR and cwEDMR have provided information about spin-pairs dominating electronic processes and their transitions in conducting polymers [28][29][30][31][32][33][34][35][36][37][38][39] , small molecules [40][41][42] , and polymer or small molecule/fullerene blends 43,44 . The effect of isotopic modification on magnetic field effects in organic semiconductors also has been observed by ODMR 45 , and the intersystem-crossing time has been extracted from the modulation frequency dependence 46 .…”

“…There has been a number of efforts to find the solutions for modulation frequency dependence 8,20,31,[37][38][39]43,46,50 . However, no closed form analytical solutions have been reported, and important aspects of modulation frequency effects remain not well understood.…”

“…sity 6,7,13,18,41,[48][49][50] (or an injection current for EDMR 30,41,51 ), temperature 6,10,30,41 , and MW power (equivalently B 1 field strength) 6,7,12,[17][18][19][20]26,40,43,46,[52][53][54][55] .…”

Estudo de processos de transporte eletrônico em dispositivos a base de semicondutores orgânicos

“…Em particular, a técnica de Ressonância Magnética Detectada Eletricamente (RMDE) tem sido empregada com sucesso no estudo dos processos de transporte e recombinação em semicondutores cristalinos [18,19,20,21], em semicondutores amorfos, micro ou policristalinos [22,23,24,25,26,27,28,29,30] e em semicondutores orgânicos [31,32,33,34,35,36,37]. aplicá-la a dispositivos poliméricos [36,37].…”