基于量子点/非晶杂化结构的SnO2薄膜紫外光电应用研究

Tin dioxide (SnO2) is a wide direct bandgap semiconductor and its bandgap is in the ultraviolet (UV) region. However, it is commonly believed that SnO2 is not a suitable UV light emitter due to the dipole-forbidden nature of its band-edge quantum states. The even-parity symmetry of the conduction-band minimum (CBM) and valence-band maximum (VBM) states in SnO2 prohibits the band-edge radiative transition and light emission, which limits its potential in optical applications such as photodiodes and light-emitting diodes (LEDs). Recent research indicates that nanostructural SnO2 can break dipole-forbidden rule and realize UV light emission. In this project, we will fabricate SnO2 thin films based on quantum-dot/amorphous hybrid structure for application in UV optoelectronic field. Research content includes: (i)explore physical mechanism of effect of hybrid component on UV spectra, intensity and dynamics of UV light emission;(ii)obtain an effective method to break dipole-forbidden rule and recover the UV optical activity; (iii)develop a technology to control size and distribution of quantum dots and modulate UV luminescent properties;(iv)study doping effect in hybrid SnO2 films, such as spectral structure of luminescence,intensity and dynamics of UV light emission as acceptor indium doped into SnO2 quantum-dots;(v)design and fabricate pn- or pin-structural UV LEDs based on SnO2 quantum-dot/amorphous hybrid thin films and elucidate the influence of device structure on performace of UV light emission. It is significant to research SnO2 thin films based on quantum-dot/amorphous hybrid structure for well understanding physical nature of breaking dipole-forbidden rule and further develop UV optoelectronic application based on SnO2 hybrid thin films.

二氧化锡（SnO2）是直接宽禁带半导体，带隙处于紫外区，其单晶导带底和价带顶的对称性决定了带边跃迁是禁戒的，限制了它在紫外光电领域的应用。不过，最近的研究表明，具有纳米结构的SnO2能够打破带边禁戒跃迁的限制，并实现紫外发光。本项目将制备包埋于非晶薄膜之中的SnO2量子点（即量子点/非晶杂化结构SnO2薄膜），以期实现高效的紫外发光。主要研究：杂化组分对薄膜光谱结构、发光强度及发光动力学影响的规律和物理机制；探寻打破偶极禁戒跃迁、实现紫外发光的有效方法；获得控制量子点尺寸与分布的技术手段；开展杂化薄膜掺杂特性研究，探索量子点中引入受主杂质In后的光谱结构、发光强度及发光动力学规律；设计和制备pn或pin异质结构的紫外发光二极管，并研究发光二极管结构对紫外发光性能的影响。本项目的研究对于深入理解SnO2量子点紫外发光动力学机制和开发SnO2薄膜紫外光电器件具有十分重要的意义。

二氧化锡（SnO2）是直接宽禁带半导体，带隙处于紫外区，其单晶导带底和价带顶的对称性决定了带边跃迁是禁戒的，严重制约了它在紫外光发射器件中的应用。虽在一维SnO2纳米结构中可观察到紫外光，但常伴有较强的可见光，并且基于纳米结构的器件成品率低，在这种情况下，探索打破偶极禁戒跃迁定则的有效方法，恢复SnO2薄膜的紫外光发射，发展基于薄膜的光电器件成为实现其紫外光电应用的重要选择。本项目正是围绕这一主题开展了如下研究工作：（1）利用纳米工程恢复其紫外光发射。制备了量子点或纳米晶/非晶杂化结构SnO2薄膜，设计制备了pn异质结紫外发光二极管原型器件，实现了室温下的紫外电致发光。（2）设计制备了基于SnO2纳米带的紫外光电二极管原型器件，紫外可见抑制比达2个数量级，395nm处光响应度为1×10-4A/W。（3）通过掺杂工程恢复紫外发光。制备了受主元素（Mg、In）掺杂的SnO2薄膜，利用MgSn和2InSn-VO复合体打破了跃迁禁戒规则，恢复了紫外发光，设计并制备了基于受主掺杂SnO2薄膜的异质结发光二极管原型器件，在电泵浦条件下，观察到了来自于SnO2有源层的紫外发光。（4）针对薄膜紫外发光效率低的问题，利用Ag纳米颗粒的表面等离激元与薄膜发光的共振耦合，进一步提高了Ag掺杂SnO2薄膜的紫外发光效率。