Tetraphenyldibenzoperiflanthene as sensitizer for enhancing the performance in dinaphthothienothiophene-based photovoltaics with and without fullerene

In this work, various interlayers were inserted between the donor and acceptor in a dinaphthothienothiophene (DNTT)/C 60 planar heterojunction (PHJ) to sensitize the performance. The power conversion efficiency is enhanced from 1.16% for the DNTT/C 60 PHJ cell to 2.23% by inserting a 5-nm-thick tetraphenyldibenzoperiflanthene (DBP) interlayer because of the greatly improved photocurrent and open-circuit voltage ( V OC ). To achieve high V OC , fullerene-free PHJs of DNTT/boron subphthalocyanine chloride (SubPc) (donor/acceptor) were fabricated, and V OC is further improved by doping various fractions of DBP into the SubPc layer. The V OC clearly increases from 0.82 V to 1.24 V by 70 wt%-DBP doping and is accompanied by a slight increase in photocurrent. The bipolar transfer characteristics of SubPc and DBP are investigated by field-effect transistors and show that both can transport electrons, indicating their potential as acceptors in photovoltaic devices. When another 5-nm-thick SubPc layer was included in the fullerene-free DNTT/SubPc:DBP PHJ cell, the power conversion efficiency further increases to 1.32%. These results indicate that DBP is a promising sensitizer for enhancing the performance of DNTT-based photovoltaics.