An easily prepared carbon quantum dots and employment for inverted organic photovoltaic devices

- Dual electron transporting layer is used in organic solar cells.
- The energy barrier for electron transport is decreased.
- The balanced charge transfer of electron and hole is achieved.
- Well contact of active layer and cathode is realized.
- Electron extraction improvement by a good energy levels tailorment.

In this paper, the performance enhancement of organic solar cells based on PCDTBT:PC71BM and P3HT:PC60BM are demonstrated via employing carbon quantum dots (CQD) to modify the metal oxide electron transport layer. The incorporated CQD with carboxylic acid (-COOH) groups could induce self-assembled monolayer (SAM) with TiO2 buffer layer, which lowered the energy barrier for electron transfer and reduced the inherent incompatibility between the metal oxide and organic active layers. Further investigation shows that SAM of TiO2 with CQD can improve the photo-induced exciton dissociation and charge transfer, leading to a low electron accumulation in charge transport layer and a reduced interface recombination loss.