Hou Jianhui

Realizing 11.3% efficiency in fullerene-free polymer solar cells by device optimization

In this work, photovoltaic properties of the PBDB-T:ITIC based-NF-PSCs were fully optimized and characterized by tuning the morphology of the active layers and changing the device architecture. First, donor/acceptor (D/A) weight ratios were scanned, and then further optimization was performed by using different additives, i.e. 1,8-diiodooctane (DIO), diphenyl ether (DPE), 1-chloronaphthalene (CN) and N-methyl-2-pyrrolidone (NMP), on the basis of best D/A ratio (1:1, w/w), respectively. Finally, the conventional or inverted device architectures with different buffer layers were employed to fabricate NF-PSC devices, and meanwhile, the morphology of the active layers was further optimized by controlling annealing temperature and time. As a result, a record efficiency of 11.3% was achieved, which is the highest result for NF-PSCs. It’s also remarkable that the inverted NF-PSCs exhibited long-term stability, i.e. the best-performing devices maintain 83% of their initial PCEs after over 4000 h storage.

Environmentally-friendly solvent processed fullerene-free organic solar cells enabled by screening halogen-free solvent additives

Though the power conversion efficiencies (PCEs) of organic solar cells (OSCs) have been boosted to 12%, the use of highly pollutive halogenated solvents as the processing solvent significantly hinders the mass production of OSCs. It is thus necessary to achieve high-efficiency OSCs by utilizing the halogen-free and environmentally-friendly solvents. Herein, we applied a halogen-free solvent system (oxylene/1-phenylnaphthalene, XY/PN) for fabricating fullerene-free OSCs, and a high PCE of 11.6% with a notable fill factor (FF) of 72% was achieved based on the PBDB-T:IT-M blend, which is among the top efficiencies of halogen-free solvent processed OSCs. In addition, the influence of different halogen-free solvent additives on the blend morphology and device performance metrics was studied by synchrotron-based tools and other complementary methods. Morphological results indicate the highly ordered molecular packing and highest average domain purity obtained in the blend films prepared by using XY/PN co-solvent are favorable for achieving increased FFs and thus higher PCEs in the devices. Moreover, a lower interaction parameter (χ) of the IT-M:PN pair provides a good explanation for the more favorable morphology and performance in devices with PN as the solvent additive, relative to those with diphenyl ether and N-methylpyrrolidone. Our study demonstrates that carefully screening the non-halogenated solvent additive plays a vital role in realizing the efficient and environmentally-friendly solvent processed OSCs.摘要虽然近年来有机太阳能电池的能量转换效率已经超过13%, 但是加工高效率有机太阳能电池的溶剂大多数是含卤溶剂, 这些溶剂体系阻碍了有机太阳能电池的进一步发展. 因此, 探索使用绿色溶剂制备高效率电池具有重要意义. 本文在非卤溶剂邻二甲苯作为主溶剂的前提下,通过筛选不同非卤溶剂作为添加剂制备高效有机太阳能电池, 在PBDB-T:IT-M共混材料体系中, 取得了11.6%的能量转换效率, 该效率是使用非卤溶剂加工有机太阳能电池的最高效率之一. 我们通过一系列形貌测试将共混薄膜形貌的相区尺寸, 相区纯度以及结晶性等重要形貌参数与器件性能进行关联, 这对非富勒烯有机太阳能电池的性能优化具有指导意义. 本研究表明, 通过细致筛选非卤溶剂添加剂调节共混薄膜的形貌, 从而可以获得高性能的有机太阳能电池.

Manipulating the nanoscale morphology in the active layers of polymer solar cells

聚合物太阳能电池由于制备工艺简单、重量轻、成本低廉、可制备大面积柔性器件等优点, 成为新能源和材料科学中的重要研究方向. 经过近10年的发展, 聚合物太阳能电池的能量转换效率从2005年的5%提高到目前的10%左右, 然而聚合物太阳能电池的活性层形貌仍是制约其能量转换效率的一个重要方面. 本文围绕聚合物太阳能电池结构与性能的关系, 重点介绍了活性层材料的分子设计(共轭主链调制、烷基侧链优化等)和加工方法(热退火、添加剂、三元溶剂、绿色溶剂等)对其微观形貌的影响, 并展望了聚合物太阳能电池未来的发展趋势以及面临的关键挑战.

Highly efficient two-dimensional conjugatedbenzodithiophene-based photovoltaic polymers

In order to improve the photovoltaic properties of polymer solar cells (PSC), varieties of donor and acceptor units were designed and synthesized to construct the highly efficient conjugated polymers. Recent years, materials based on benzo [1.2-b:4,5-b ¢ ]dithiophene (BDT) units have showed promising applications in the field of organic photovoltaics for its excellent properties. As compared to BDT-based polymers with flexible side chains, polymers based on two-dimensional conjugated BDT (2D-BDT) usually had better thermal stability, slightly red-shifted of absorption spectra, lower HOMO levels, higher hole mobility and consequently improved photovoltaic properties. By using novel 2D-BDT-based polymers, the power conversion efficiency (PCE) of the PSC devices has been boosted to over 10%. In this article, we first briefly introduce the synthesis methods of 2D-BDT unit, and then focus our attention to summarize the numerous of 2D-BDT-based polymers and their applications in highly efficient PSC devices.