Strain-Enhanced Formation of Delocalized Exciton States in Phthalocyanine Crystalline Thin Films
Strain-Enhanced Formation of Delocalized Exciton States in Phthalocyanine Crystalline Thin Films
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DOI：
10.1021/acs.jpcc.2c01382
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发表时间：
2022-05
期刊：
影响因子：
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通讯作者：
Libin Liang;Katrina Czar;M. Furis
中科院分区：
文献类型：
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作者：
Libin Liang;Katrina Czar;M. Furis
在有机半导体中，离域激子态的形成是非常可取的，因为它导致器件中有效的能量传输。我们研究了单轴应变作为可溶性八羧基酞菁晶体薄膜中离域激子（即激子-极化子）的“调谐盘”的潜力。吸收光谱和光致发光光谱证实了在拉伸应变存在的情况下，离域激子态的形成，伴随着拉曼光谱中低频振动模式（<100 cm-1）的红移，这可能是离域激子形成的原因。值得注意的是，当拉伸应变为4.9%时，光致发光强度增强了80%，峰值波长红移了30 nm，相当于在室温下温度降低了约100 K。这些结果表明，应变工程可以有效地改变八叔甲氧基酞菁晶体薄膜中的激子-声子耦合，使其在室温下实现离域。
The formation of delocalized excitonic states in organic semiconductors is highly desirable because it leads to efficient energy transport in devices. We investigate the potential of uniaxial strain as a “tuning dial” for delocalized excitons (i.e., exciton–polarons) in crystalline thin films of soluble octabutoxy phthalocyanine. Absorption and photoluminescence spectra confirm the formation of delocalized excitonic states in the presence of tensile strain, accompanied by a red shift of low-frequency vibration modes (<100 cm–1) in Raman spectroscopy, which are likely responsible for the delocalized exciton formation. Remarkably, an 80% enhancement in photoluminescence intensity and a 30 nm red shift in peak wavelength are observed for a tensile strain of 4.9%, which is equivalent to a temperature reduction approximately by 100 K below room temperature. These results show promise that strain engineering can efficiently modify the exciton–phonon coupling in octabutoxy phthalocyanine crystalline thin films toward enabling delocalization at room temperature.