The Molecular Structures of Poly(3-hexylthiophene) Films Determine the Contact Properties at the Electrode/Semiconductor Interface

Abstract

The contact properties between gold and poly(3-hexylthiophene) (P3HT) films having either of two distinct molecular orientations and orderings were investigated. Thermal treatment increased the molecular ordering of P3HT and remarkably reduced the contact resistance at the electrode/semiconductor interface, which enhanced the electrical performance. This phenomenon was understood in terms of a small degree of metal penetration into the P3HT film as a result of the thermal treatment, which formed a sharp interface at the contact interface between the gold electrode and the organic semiconductor.

Charge transport in nanoscale vertical organic semiconductor pillar devices

“…In the case that also on Au electrodes in our devices the first few nanometers have an edge-on orientation, the conductivity of the devices with 10 nm and 5 nm P3HT thickness would be much less than in the simulations, in accordance with our finding. Edge-on orientation of P3HT at the interface with Au after an annealing procedure has indeed been reported5859. For the thicker devices the effect will be much weaker, because the conductivity is then governed by the bulk.…”

Charge transport in nanoscale lateral and vertical organic semiconductor devices

“…In the case that also on Au electrodes in our devices the first few nanometers have an edge-on orientation, the conductivity of the devices with 10 nm and 5 nm P3HT thickness would be much less than in the simulations, in accordance with our finding. Edge-on orientation of P3HT at the interface with Au after an annealing procedure has indeed been reported [60,61]. For the thicker devices the effect will be much weaker, because the conductivity is then governed by the bulk.…”

“…The injected charge carriers become space charge (excess charge) nearby the injecting electrode, building up electric potential and hence limiting the charge carrier injection. When the space charge is maximal, the obtained maximum current in an organic semiconductor is referred to as space charge limited current (SCLC) [59,60]. The SCLC is described by the Mott-Gurney equation [61]:…”

Injeção de cargas no polímero P3HT em condições ambientais como um controle de processos degradativos em materiais verdes

“…O advento dos polímeros conjugados à base de Tiofeno, chamou atenção e o interesse de pesquisadores por materiais poliméricos condutivos e suas aplicações [19]. O Tiofeno mais amplamente estudado atualmente é o poli(3-hexiltiofeno)(P3HT) [49], sendo um dos mais utilizados como camada ativa em dispositivos orgânicos de alta performance como transistores de efeito de campo (OFETs), células orgânicas fotovoltaicas (OPV) [19,[49][50][51][52][53][54][55], sensores químicos orgânicos voláteis (VOC) [56], OLEDs, dispositivos ópticos não lineares, músculos artificias, entre muitas outras [53]. Seu sucesso se deve ao fato de possuírem favorável processabilidade, relativa estabilidade química [57], boa solubilidade em vários solventes [51], elevado transporte de carga (0.2 cm 2 /V.s), propriedades de alteração eletrônica por processos químicos [56], uma vez que possuem baixos bandgaps (Eg = 1.9 eV) [50,58], dentre outras.…”

“…Em se tratando do contato eletrodo de topo e semicondutor, Park [54] menciona o fato da migração do metal para o polímero. O desempenho de transistores de P3HT são influenciados pela interface metal-semicondutor, cuja penetração é mais crítica em filmes não tratados termicamente e depende de mudanças na orientação molecular e ordenação do P3HT.…”