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Advanced functional materials: crystal plane control -- a new way to suppress defects in colloidal quantum dots

wallpapers Cruise 2020-08-27

colloidal quantum dots are semiconductor nanoparticles synthesized by solution process. Due to the significant quantum confinement effect they show adjustable size b gap are potential optoelectronic materials. Solar cells based on colloidal quantum dots (QDs) are an important new type of photovoltaic devices which have the following advantages: low cost solution preparation; significant multiple exciton generation effect (carrier doubling) of quantum dots (PBS PbSe PbTe etc.) which can surpass the limit of traditional Shockley queisser theory increase the theoretical efficiency of single junction solar cells from 33% to 44%; due to the adjustable b size the solar cells with single junction have high efficiency Quantum dots can be used in high efficiency single junction cells narrow b gap (< 1.1 EV) infrared solar cells to capture low-energy infrared photons that can not be used by conventional cells (such as silicon-based perovskite cells) to make up for the lack of spectral utilization.

at present the most widely used material in quantum dot solar cells is lead sulfide (PBS) colloidal quantum dots the highest certification efficiency has reached 12.5%. Defect control is the key to improve the performance of quantum dot solar cells recent studies show that the {100} surface of PbS quantum dots is the main source of defects. At present most of the research also focuses on the surface passivation of PbS quantum dots the development of new lig exchange schemes to eliminate defects such as "treating congenital defects".

Zhang Jianbing's team collaborators of Huazhong University of science technology changed their thinking expecting to suppress {100} surface in the synthesis process of quantum dots avoid defects from the source directly obtain "healthy" PbS quantum dots. Based on the cation exchange synthesis method they control the dynamic thermodynamic balance in the growth process of quantum dots to achieve effective crystal plane control. The results show that the geometric structure of 3 nm PbS quantum dots grown by anisotropic growth of quantum dots is approximately octahedral the surface contains almost only {111} crystal planes; while the growth of quantum dots is isotropic under the growth condition dominated by thermodynamics the geometric structure of the obtained quantum dots is octahedral with {111} {100} crystal planes. Therefore the efficiency of photovoltaic devices based on QDs with almost only {111} facets is as high as 11.5% which is 25% higher than those with both {111} {100} facets. The work of

has promoted the synthesis of PbS quantum dots to a new height which is no longer confined to size control size uniformity surface passivation. Through crystal plane control defects are avoided from the source which provides a new way for the performance optimization of quantum dot optoelectronic devices. The related work is entitled "facet control for trap state suppression in colonial quantum dot solids" published online in advanced functional materials( DOI:10.1002/adfm.202000594 )Go ahead. The first authors are Dr. Xia Yong of Huazhong University of science technology Dr. Chen Wei of Munich University of technology. This work is supported by National Natural Science Foundation of China Professor Peter M ü ller buschbaum of Munich University of technology.


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