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

•DBP was added for fabricating the DNTT/DBP/C60 cascade PHJ.•The cascade PHJ resulted in 17% and 92% enhancement in VOC and PCE, respectively.•SubPc and DBP both indicated bipolar transport.•VOC of fullerene-free PHJ of DNTT/SubPc was improved by doping DBP into SubPc.•VOC increased from 0.82 V to 1.24 V by 70 wt%-DBP doping in fullerene-free PHJ.

In this work, various interlayers were inserted between the donor and acceptor in a dinaphthothienothiophene (DNTT)/C60 planar heterojunction (PHJ) to sensitize the performance. The power conversion efficiency is enhanced from 1.16% for the DNTT/C60 PHJ cell to 2.23% by inserting a 5-nm-thick tetraphenyldibenzoperiflanthene (DBP) interlayer because of the greatly improved photocurrent and open-circuit voltage (VOC). To achieve high VOC, fullerene-free PHJs of DNTT/boron subphthalocyanine chloride (SubPc) (donor/acceptor) were fabricated, and VOC is further improved by doping various fractions of DBP into the SubPc layer. The VOC 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.

Graphical abstractSmall molecule DBP was added as an interlayer for a DNTT cascade PHJ cell, or was used as a dopant in the SubPc layer in a fullerene-free DNTT PHJ cell to enhance the performance.Figure optionsDownload full-size imageDownload as PowerPoint slide