An inverted architecture P3HT:CdSe bulk-heterojunction hybrid solar cell utilizing a quantum junction with high open circuit voltage and efficiency

Exploring CdSe QDs as a substitute for [6,6]-phenyl-C61 butyric acid methyl ester (PCBM) in Poly (3-hexylthiophene) (P3HT) based photovoltaic devices received much attention due to its properties such as tunable band gap over the visible range, better band alignment with P3HT and inexpensiveness. But, the VOC values of the P3HT:CdSe QDs bulk-heterojunction (BHJ) hybrid solar cells are still inferior, which happens to be the main performance-limiting factor for these devices. We have resolved this issue in this study by the application of an interfacial buffer layer (BL) in an inverted architecture utilizing zinc oxide (ZnO) as an electron transporting layer. The BL was also formed of CdSe QDs. It was found that the application of the interfacial BL reduces the interface recombination which resulted in a VOC value of 0.96 V. To the best of our knowledge, this is the best VOC value reported for the P3HT:CdSe QDs BHJ system so far. A quantum junction (QJ) was also formed between the QDs in the BL and the QDs in the BHJ by passivating them with Iodine and 3-Mercaptopropionic acid (MPA), respectively. The QJ induces an extended electric field in the BHJ which benefits charge extraction and ultimately resulting in an enhanced short circuit current (JSC).