可溶液加工的D-A-D型有机小分子的烷基链效应及光电性能

设计合成了3种可溶液加工的基于噻吩给体和2-吡喃-4-亚基丙二氰(PM)受体的新型Donor-Acceptor-Donor(D-A-D)型有机小分子TPT-N, TPT-S和TPT-D. 研究了噻吩给体单元上烷基链的数目对分子的溶解性、 光物理(吸收特性)、 热稳定和光电性能的影响. 结果表明, 随着烷基链的增加, 分子的溶解性增加, 成膜性能提高; 分子在溶液中的吸收光谱发生红移, 薄膜的吸收谱带变窄, 分子的最高占有分子轨道(HOMO)能级提高. 以D-A-D型有机小分子为给体, 富勒烯C₆₀衍生物-苯基-C₆₁-丁酸甲酯(PCBM)为受体制备了结构为ITO/PEDOT∶PSS/D-A-D∶PCBM/LiF/Al的体异质结太阳能电池. 研究结果表明, 基于单烷基链的TPT-S的太阳能电池具有相对较高的能量转换效率. 说明在D-A-D型有机小分子太阳能电池材料中, 烷基链的数目是决定材料性能及器件性能的重要因素之一.

Alkyl Chain Effect and Photoelectric Properties of D-A-D Structural Solution Processable Organic Small Molecules

Three novel solution processable organic small molecules,TPT-N,TPT-S and TPT-D with a Donor-Acceptor-Donor(D-A-D) structure based on thiophene donor unit and 2-pyran-4-ylidenemalononitrile(PM) acceptor unit,were designed and synthesized.Effect of alkyl chain number on the solubility,photophysical properties(absorption characteristic),thermal stability and photoelectric properties of the molecules were investigated.The results indicate that with the alkyl chain increasing the solubility and film-forming pro-perties of the molecules increase,and the absorption spectra of the organic small molecules are red-shifted in solutions and the absorption bands in films become narrow.Moreover,the highest occupied molecular orbital(HOMO) energy levels also increase with the alkyl chain of the molecules increasing.Bulk heterojunction structural solar cells with a device structure of ITO/PEDOT∶PSS/D-A-D∶PCBM/LiF/Al based on the D-A-D organic small molecules as the donor,(6,6)-phenyl C61-butyric acid methyl ester(PCBM) as the acceptor were fabricated.It is found that the device based on TPT-S which has a single alkyl chain on the thiophene unit has a relatively high power conversion efficiency(PCE).The research results confirm that the alkyl chain number is one of the most important effects that influence the properties of the materials and device perfor-mance as for D-A-D organic small molecular solar cell materials.