Zhang Shaoqing

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.