【作者】 王宁；

【导师】 刘俊；

【作者基本信息】 中国科学技术大学 ， 高分子化学与物理， 2021， 博士

【摘要】 全高分子太阳能电池(all-PSCs)以高分子给体和高分子受体的共混物作为活性层,具有稳定性优异和力学性质好的突出优势,在柔性光伏领域的应用前景广阔。发展高性能全高分子太阳能电池的难点在于活性层中高分子给体和高分子受体的共混相分离形貌调控,其共混相分离形貌常存在相区尺寸偏大和相区纯度偏低的问题。常用的共混相分离形貌调控方法,例如,热退火、溶剂退火和溶剂蒸汽退火等,在全高分子太阳能电池中的作用非常有限,无法实现器件效率的大幅度提高。其根本原因在于,高分子链的尺寸大,成膜过程中高分子链在溶液中的扩散非常缓慢。因此,迫切需要根据高分子自身的特点,开发适合全高分子太阳能电池活性层相分离形貌调控的方法。针对前述问题,基于高分子在溶液中的扩散慢的特点,采用硼氮配位键高分子受体材料,本论文提出“通过控制高分子给体/高分子受体在溶液中的聚集状态来调控全高分子太阳能电池活性层形貌”的策略,通过溶液的配制方式、溶液的温度调控、高分子的分子量优化三种方法,实现了对高分子给体/高分子受体相分离形貌的调控和全高分子太阳能电池器件性能的提升。在此基础上,通过采用高效高分子受体材料,发展出能量转换效率超过15%的全高分子太阳能电池器件。具体内容如下:(一)高分子给体/受体分开溶解配制溶液的方式对相分离形貌的影响用于旋涂制备活性层的高分子给体/受体的溶液,其传统的配制方式是将两种高分子一起溶解,导致成膜过程中两种高分子的相分离程度偏低,不利于全高分子太阳能电池器件效率的提升。针对该问题,我们基于高分子给体J61和高分子受体PBN-10,利用高分子链在溶液中自聚集、扩散慢的特点,通过将高分子给体和高分子受体各自分开溶解,再共混配制溶液,并立即旋涂制备活性层,实现了活性层中高分子的结晶性提升、相分离尺寸增大和相区纯度提高,因此实现了器件短路电流和填充因子的提升。采用传统一起溶解的溶液配制方式的器件能量转换效率为5.36%,而采用分开溶解的溶液配制方式的器件能量转换效率提高到7.09%。(二)调控高分子溶液温度提高结晶性并减小相区尺寸高分子给体/受体在溶液中形成自聚集,其聚集程度具有温度依赖性,因此,我们提出通过控制高分子给体/受体溶液的温度,实现对全高分子太阳能电池活性层相分离形貌的调控。基于高分子给体CD1和高分子受体PBN-12,研究结果表明,随着溶液温度的提升,活性层中高分子的结晶性先增加再降低,相分离尺寸先减小再增加。在高分子溶液温度为90℃时,活性层表现出最小的相区尺寸和优异的结晶性,实现了最高的能量转换效率。此优化温度下,全高分子太阳能电池的能量转换效率达到10.1%,高于溶液温度为室温所得到的器件效率。(三)高分子给体/受体的分子量对相分离形貌的影响我们选择数均分子量分别为14.0、35.5和56.1 kg mol-1的高分子给体CD1和数均分子量分别为32.7、72.4和103.4 kg mol-1的高分子受体PBN-14,系统地研究了高分子给体和高分子受体的分子量对全高分子太阳能电池相分离形貌和器件性能的影响。研究结果表明,高分子材料的分子量越高,其在溶液中的聚集越强;当高分子给体/受体中有一种具有较高分子量时,其共混形貌表现出明显的双连续纤维网络结构;随高分子给体或受体的分子量增加,高分子给体或高分子受体的分子量对器件性能的影响逐渐减弱;当高分子给体CD1和高分子受体PBN-12的分子量均为适中的35.5 kg mol-1和72.4 kg mol-1时表现出较优的共混相分离形貌,获得了最高的器件性能,PCE达10.1%。(四)通过调控高分子在溶液中聚集状态发展高效率全高分子太阳能电池基于课题组开发的含硼氮配位键的高分子受体PBN-25,将其与高分子给体PM6匹配,通过调控高分子溶液的配制方法、高分子溶液的静置时间和高分子的加热溶解时间等,精细调控了 PM6和PBN-25在溶液中的聚集状态,最终发展出能量转换效率超过15%的全高分子太阳能电池。更多还原

【Abstract】 All-polymer solar cells(all-PSCs)use a blend of polymer donors and polymer acceptors as the active layer,which have outstanding advantages of excellent stability and good mechanical properties,and have broad application prospects in the field of flexible photovoltaics.The difficulty in developing high-performance all-PSCs lies in the control of the blended phase separation morphology of the polymer donor and polymer acceptor in the active layer,and its blended phase separation morphology often has the problems of large phase domain size and low phase domain purity.Commonly used blending phase separation morphology controlling methods,such as thermal annealing,solvent annealing,and solvent vapor annealing,have very limited effects in all-PSCs,and cannot achieve substantial improvements in the photovoltaic performance of the device.Therefore,there is an urgent need to develop some methods suitable for phase separation morphology control of the active layer of all-PSCs based on the characteristics of the polymer itself.In response to the aforementioned problems,based on the slow diffusion of polymers in solution,the use of boron-nitrogen coordination bond polymer acceptor materials,this paper has proposed the core strategy of "controlling the active layer morphology of all-PSCs by controlling the pre-aggregation of polymer donors/acceptors in solution".By changing the solution preparation method,controlling the temperature of the solution,and optimizing the molecular weight of the polymer,the regulation of the phase separation morphology of the polymer donor/polymer acceptor and the improvement of the performance of the all-PSCs devices are realized.On this basis,through the use of high-efficiency polymer acceptor materials,an all-PSC device with a power conversion efficiency of more than 15%has been developed.The details are as follows:1.The influence of the way of dissolving the polymer donor/acceptor separately to prepare the solution on the phase separation morphologyThe polymer donor/acceptor solution used to prepare the active layer by spin coating,and the traditional preparation method is to dissolve the two polymers together,resulting in a low degree of phase separation of the two polymers during the film formation process,which is not conducive to the improvement of the efficiency of all-PSCs.In response to this problem,based on the polymer donor J61 and the polymer acceptor PBN-10,we take advantage of the self-aggregation and slow diffusion of polymer chains in the solution,by dissolving the polymer donor and polymer acceptor separately,then blending to prepare the solution,and immediately spin coating to prepare the active layer,the crystallinity of the polymer in the active layer is improved,the phase separation size is increased,and the phase domain purity is improved.Therefore,the short-circuit current and fill factor of the device are improved.The power conversion efficiency of the device using the traditional solution preparation method of dissolving together is 5.36%,while the power conversion efficiency of the device using the solution preparation method of dissolving separately is increased to 7.09%.2.Control the temperature of the polymer solution to increase the crystallinity and reduce the phase domain sizeThe polymer donor/acceptor forms self-aggregation in the solution,and the degree of aggregation is temperature-dependent.Therefore,we propose controlling the phase separation morphology of the active layer of all-PSCs by controlling the temperature of the polymer donor/acceptor solution.Based on the polymer donor CD 1 and the polymer acceptor PBN-12,the research results show that as the solution temperature increases,the crystallinity of the polymer in the active layer first increases and then decreases,and the phase separation size first decreases and then increases.When the polymer solution temperature is 90℃,the active layer exhibits the smallest phase domain size and excellent crystallinity,achieving the highest power conversion efficiency.Under this optimized temperature,the power conversion efficiency of the all-PSC reaches 10.1%,which is higher than the device efficiency obtained at room temperature.3.The influence of molecular weight of polymer donor/acceptor on phase separation morphologyWe selected the polymer donor CD1 with number average molecular weights of 14.0,35.5,and 56.1 kg mol-1 and the polymer acceptor PBN-14 with number average molecular weights of 32.7,72.4 and 103.4 kg mol-1,and systematically studied the influence of the molecular weight of the polymer donor and polymer acceptor on the phase separation morphology and device performance of all-PSCs.The research results show that the higher the molecular weight of the polymer material,the stronger its aggregation in the solution;when one of the polymer donors/acceptors has a higher molecular weight,the blend morphology shows obvious bicontinuous fibers network structure;As the molecular weight of the polymer donor or acceptor increases,the influence of the molecular weight of the polymer donor or polymer acceptor on the performance of the device gradually weakens;When the molecular weights of the polymer donor CD1 and the polymer acceptor PBN-12 are both moderately 35.5 kg mol-1 and 72.4 kg mol-1,they show a better blended phase separation morphology and obtain the highest device performance,PCE reached 10.1%.4.Develop high-efficiency all-polymer solar cells by controlling the aggregation state of polymers in solutionBased on the polymer acceptor PBN-25 containing boron-nitrogen coordination bond developed by the research group,it was matched with the polymer donor PM6,by adjusting the preparation method of the polymer solution,the aging time of the polymer solution and the heating time of the polymer solution,the aggregation state of PM6 and PBN-25 in the solution is finely controlled,and finally developed an all-PSC with a PCE of more than 15%.更多还原