High-efficiency, low-cost quantum dots (QDs) sensitized solar cells (QDSCs) are achieving considerable academic as well industrial interest, due to promising optoelectronic properties of QDs such as size-tunable band gap, high absorption coefficient, large dipole moment, solution processability and the possibility of multiple exciton generation. However, the highest photoconversion efficiency (PCE) of QDSCs reaches to only 12.07%, still lower than the commercial silicon solar cells (typical in the range of 20-40%) due to serious of carrier recombination at the interfaces or within the QDs. This demands the further development of highly efficient QDs to be applied as light harvester to boost the PCE of QDSCs, as the QDs have the immense potential and easy to control their optoelectronic properties. The surface passivation of QD core with shell layer of different materials/thickness has been shown to be an effective approach, which offers a significantly enhanced quantum yield (QY), prolonged PL lifetime and improved chemical, thermal and photo-chemical/physical stability compared to bare QDs due to the reduced density of surface trap states/defects and optimized electronic band alignment between core and shell. Apart from the improvement in conversion efficiency, device fabrication costs and stability over the time are also taken as a significant part of this work, because these factors are equally important in order to shift the device from the laboratory to a real market product. Herein, we present for the first time, “Giant” core/shell CdSe/(CdS)x QDs with tunable CdS shell thickness, while keeping the same core size, synthesized via a hot-injection approach, as a highly efficient and stable light harvester in QDSSCs. We will discuss the benefits of core/shell QDs interface engineering in terms of shell thickness to improve efficiency and long-term stability of liquid junction QDSCs. In addition, the highly beneficial role of a CdSexS1-x interfacial alloyed layer between CdSe core and CdS shell, yielding a maximum PCE of 6.86% due to favorable stepwise electronic band alignment and improved electron transfer rate with respect to CdSe/(CdS)x core/shell, will be also presented and discussed.

Highly stable giant core/shell colloidal quantum dot sensitized solar cells

254th National Meeting (2017)

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