嵌段共聚物自组装结合ALD技术原位构筑稳定有序杂化纳米结构及其p-i-n型光伏电池

Formation of intimate contact between conjugated polymers and inorganic semiconducting nanocrystals (NCs), achievement of stable and well-ordered hybrid nanostructures with the phase separation size equal to the exciton diffusion length and fabrication of solar cells with the p-i-n structure can effectively improve the efficiency and stability of conjugated polymer/inorganic semiconductor hybrid solar cells. In this project, the all-conjugated amphiphilic block copolymers are rationally designed and synthesized. The all-conjugated amphiphilic block copolymers can self-assemble to form well-ordered lamellar microphase separation nanostructures with thermodymamic stability. Then stable and ordered hybrid nanostructures will be fabricated in-situ based on the self-assembled template of block copolymers via atomic layer deposition (ALD) technique. By the application of the coordination between the polar side chains of hydrophilic segments and metal ions, the growth of NCs can be confined in hydrophilic segments. The effect of self-assembled template microstructure on the domain sizes and distribution of NCs will be investigated. Such approach can strictly confine the phase segregation size of hybrid system in 10-20 nm and realize the ordered distribution of NCs in organic matrix to obtain the ordered hybrid nanostructres to improve the efficiencies of exciton dissociation, carriers transport and collection. The influence of the polar side chain molecular structures of hydrophilic segments and growth condition on the size, morphology and surface state of NCs will be observed. And the well-defined and intimate polymers-semiconductor and adjacent NCs/NCs interface will be achieved to facilitate the photoinduced charge separation and carriers transport. The effect of ALD growth condition on the vertical distribution of NCs will also be investigated and the p-i-n photovoltaic device will be fabricated to improve photon absorption and decrease charge recombination. Meanwhile, the relationship between thermodymamic stability of block copolymer self-assembled template and hybrid system stability will be researched and the stability mechanism will be discussed to improve the stability of hybrid solar cells.

形成具有紧密接触杂化界面、相分离尺度严格控制在激子扩散长度范围的稳定有序杂化纳米结构，构建p-i-n型电池是提高杂化太阳电池效率和稳定性的关键。本项目以全共轭两亲性嵌段共聚物自组装形成的热力学稳定的层状有序纳米结构为模板，采用原子层沉积技术，原位构建有序杂化纳米结构及其p-i-n光伏电池。利用亲水嵌段对金属离子的配位能力，将纳米晶生长限制在亲水相，研究聚合物自组装对纳米晶区尺度、分布的影响，实现相分离尺度严格控制在10-20nm，且有序分布，提高激子分离、载流子传输和收集效率；研究亲水嵌段结构和生长条件对纳米晶尺寸、形貌和表面态的原位调控机制，形成紧密接触的杂化界面，提高电荷转移效率，增强纳米晶之间电荷传输；研究生长条件对纳米晶纵向分布的影响，获得p-i-n型器件，提高光吸收，降低电荷复合几率；研究热力学稳定的嵌段共聚物自组装结构与杂化纳米结构稳定性之间的关联，探讨稳定机制，提高稳定性。

以共轭聚合物为电子给体，无机半导体纳米晶为电子受体构建的有机-无机杂化太阳电池因兼具高分子材料良好柔韧性、可加工性，质量轻等优点，以及无机半导体纳米晶电子迁移率高、良好物理和化学稳定性、光学性能可调的特点，成为研究热点。形成具有紧密接触杂化界面、相分离尺度严格控制在激子扩散长度范围的稳定有序杂化纳米结构，构建p-i-n型电池是提高杂化太阳电池效率和稳定性的关键。本项目充分利用原子层沉积（ALD）原位生长无机纳米晶技术和全共轭两亲性嵌段共聚物自组装形成的热力学稳定的有序微相分离纳米结构，构建具有紧密接触杂化界面的稳定有序杂化本体异质结，结合器件优化，制备高效稳定杂化太阳电池。研究发现，采用ALD技术，在共轭聚合物基质中原位生长无机半导体纳米晶，能够获得具有紧密接触杂化界面的杂化本体异质结纳米结构，从而有效提高激子分离和电荷转移效率，改善杂化器件光电性能。其次，将全共轭两亲性嵌段共聚物作为添加剂应用到杂化体系中，能够充分利用全共轭两亲性嵌段共聚物的自组装行为，以及亲水性嵌段与无机半导体纳米晶极性表面之间强的相互作用，有效改善共轭聚合物和无机半导体纳米晶之间的相容性，增强共轭聚合物链段的结晶性和有序堆砌，形成稳定的、具有紧密接触杂化界面的纳米结构，从而利于激子有效分离、电荷转移和载流子传输，提高杂化太阳电池的效率和热稳定性。以上研究工作表明，利用ALD原位生长技术和全共轭两亲性嵌段共聚物自组装行为能够有效调控无机半导体纳米晶分布，构建紧密接触的杂化界面，实现在纳米尺度上对杂化本体异质结微观结构和光物理性能的调控。该项目的实施为提高杂化太阳电池效率和稳定性提供有效策略。此外，本课题组还在采用金属离子掺杂的氧化镍空穴传输材料和引入界面小分子层来提高有机-无机杂化钙钛矿太阳电池的效率和稳定性，以及利用类卤素原位钝化钙钛矿纳米晶，提高荧光量子产率和稳定性等方面进行部分研究工作，为实现高效稳定钙钛矿太阳电池和制备高荧光稳定的钙钛矿纳米晶提供新思路。