In this study, it has been found that a very fine nanostructure can be realized by mixing 1-chloronaphthalene (CN) – a high-boiling solvent –into a binary chlorobenzene (CB) : 1,8-diiodooctane (DIO) solvent mixture to form a ternary solvent system. An improvement in energy level alignment is also obtained by doping ICBA into a binary PTB7 : PCBM blend, whereby the ternary solute system provides a new pathway for charge transfer from PTB7 to the PCBM : ICBA alloy. This is confirmed by imaging the surface morphology of the active layer using AFM and TEM, monitoring the transient film formation process and measuring the charge transfer states with Fourier transformphotocurrent spectroscopy. An encouraging PCE of 7.65% is achieved from the dual ternary system, which is the highest value ever reported for an ITO-free inverted polymer solar cell with a PEDOT:PSS layer as the top semitransparent electrode – a system which is compatible with low-cost large-area roll-to-roll manufacturing.
Zuosheng Peng,Yuxin Xia,Feng Gao,Kang Xiong,Zhanhao Hu,David James,Junwu Chen,Ergang Wang and Lintao Hou.