基于反蛋白石光子晶体结构的Cu2ZnSnS4量子点敏化太阳能电池的制备及性能研究

We present a novel design for the manufacture of sensitized solar cells, coupling high surface-to-volume ratio p-type Cu2ZnSnS4 (CZTS) quantum dots into a three-dimensional inverse opal photonic crystal. Cu2-II-IV-VI4 quaternary compounds, such as CZTS and Cu2ZnSnSe4 (CZTSe), have attracted considerable attention and been considered as one of the most promising 'next generation' photovoltaic materials due to their near-optimum direct band gap energy of 1.4～1.6 eV, large absorption coefficient (>104 cm-1) and theoretical limit power conversion efficiency of 32.2%. We develop an energy-saving hydrothermal method for synthesizing ultrafine earth abundant CZTS nanocrystals with controllable size and tunable band-gap.The inverse opals templates used for absorbing quantum dots are fabricated through infiltrating ZnO or TiO2 precursor into the interstices of the opal templates self-assembled from monodisperse submicrometer polystyrene (PS) spheres. The inverse opal and quantum dot based structure shows many advantages and plays a key role in the whole solar cell device. First, its complicated nanostructure is able to effectively diffract photons and increases their path length and dwell time within the absorber layer. Furthermore, the ordered photonic structure itself has a band-gap in the range of visible light and all the photons in the range of this band-gap can be absorbed totally. Second, its quite large surface-to-volume ratio helps to increase the contact area with the quantum dots. The dimensions of both phases (inverse opal and quantum dots) can be controlled to ensure that every contact spot is within an exciton diffusion length of an interface between the two semiconductors. Thus, it can help to further enhance the sensitization efficiency. Third, after excitons are dissociated by electron transfer, the electrons and holes have straight pathways to the electrodes. The ordered structure ensures that the carriers escape the device as quickly as possible. Based on these advantages, we believe that this novel structure made with quantum dots infiltrated into inverse opals can improve the ability of absorbing light, seperating hole-electron pair and transferring carriers, and obtain the highest possible open-circuit voltage and power conversion efficiency. We hope that this idea and design will assist us in finding a way to produce efficient photovoltaic cells.

我们设计一种基于新型量子点吸光材料和光子晶体结构的太阳能电池。将反蛋白石光子晶体结构引入太阳能电池，与p型Cu2ZnSnS4（CZTS）量子点结合封装成改进效率的太阳能电池。我们采用节能环保可靠可行的水热法制备无毒廉价高吸光度和能量转化效率的CZTS量子点。通过自组装方法制备光子晶体正模板，并通过反填制得二氧化钛和氧化锌反蛋白石光子晶体，作为吸附量子点的模板。反蛋白石结构光子晶体在这个太阳能电池设计中同时发挥三个优点：光学带隙和慢光效应利于吸光、大的比表面积利于增加和量子点接触利于敏化、有序结构利于光生载流子疏运。最终通过反蛋白石模板吸附量子点得到一种全新的基于反蛋白石光子晶体的CZTS量子点敏化太阳能电池，渴望能有效提高太阳能电池的短路电流、开路电压、填充因子和能量转化效率。通过总结提出这个电池的光生载流子的产生和疏运机制，为新型量子点太阳能电池器件发展提供充分的理论依据。

本课题集中于一种基于新型量子点吸光材料Cu2ZnSnS4（CZTS）和光子晶体结构的研究。着重研究基于CZTS及相关硫化物的量子点的制备、表征及相关量子限制效应研究。通过选择不同的前躯体溶液，运用低温节能的水热法制备多种亲水和亲油的三元和四元硫化物量子点。此外，我们制备了基于CZTS材料的空壳光子晶体结构，研究.光子晶体结构与吸光性能的关系。最后我们尝试了将反蛋白石光子晶体结构引入太阳能电池，与p型CZTS量子点结合封装成太阳能电池。通过本课题研究提出硫化物量子点的可控合成和硫化物光子晶体的可控制备，为新型量子点太阳能电池器件发展提供充分的理论依据。