A novel small molecule based on dithienophosphole oxide for bulk heterojunction solar cells without pre- or post-treatments

- A dithieno[3,2- b:2′,3′- d ]phosphole oxide-based small molecule was synthesized.
- This is the first time employing DTP unit in small molecule donor.
- The solar cells using this molecule exhibited a PCE of 5.04%.
- Morphology analyses revealed the appropriate domain size less than 20 nm.
- Bi-continuous interpenetrating paths having ordered structure were also shown.

A novel small molecule (PDTP-WR) with a dithieno[3,2- b:2′,3′- d ]phosphole oxide (DTP) core unit was designed and synthesized for use in BHJ solar cells. This small molecule had an optical band gap of 1.65 eV, appropriate for a donor material, and HOMO and LUMO energy levels of −5.10, and −3.45 eV, respectively, which provided a broad absorption and superior charge transfer properties. The solar cell devices prepared using PDTP-WR and PC71BM gave a promising power conversion efficiency of 5.04%, a Jsc of 12.98 mA cm−2, a Voc of 0.79 V, and a fill factor of 49%, without pre- or post-treatments. Morphological and structural studies revealed that PDTP-WR formed a favorable BHJ morphology. An appropriate domain size of less than 20 nm and bi-continuous interpenetrating paths with an ordered structure obtained as a result of strong intermolecular interactions can support the device performances. This is the first reported use of DTP in small molecule donor, and the results of these studies indicated that DTP-based small molecule can be a promising candidate for the photovoltaic applications.

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