Enhanced Power-Conversion-Efficiency of Silicon Solar Cells Via Energy-Down-Shift Using Energy Tuning Effect for Mn Doped Cd0.5Zn0.5s/ZnS Core/Shell Quantum Dots
Authors: Lee Seung-Jae , Ko Yun-Hyuk , Jalalah Mohammed , Shim Tae-Hun , Park Jea-Gun 
Published: February 2020

In recent study, silicon solar cell performance has been greatly progressed due to mature understanding about silicon material properties and fabrication process optimization. However, the power-conversion-efficiency (PCE) of silicon solar cells has increased slowly for last 10 years. In order to overcome the current limitation of the PCE of silicon solar-cells, our group has introduced the silicon-solar-cells implemented with core/shell quantum dots for energy conversion. According to our previous work on enhancing the efficiency of silicon solar cells via energy-down-shift using undoped CdSe/ZnS and Cd0.5Zn0.5S/ZnS core/shell QDs1-3, the Stockes’s shift was relatively small (52 – 127 nm) and that led probably to partial self-reabsorption between core/shell QDs. For that reason, we employed the doping QDs systems in this work in order to increase the Stocks’s shift to be higher than 200 nm, called energy-down-shift using energy-tuning-effect. It is known that Mn2+ doped QDs usually have large Stokes’s shift and that will help to limit the self-quenching and self-reabsorption phenomenon and, hence, increase the quantum yield of QDs4. We investigated the enhanced PCE effect of Mn2+-doped Cd0.5Zn0.5S/ZnS core/shell QD via energy-down-shift using energy-tuning-effect.

The Mn2+ doped Cd0.5Zn0.5S/ZnS core/shell QDs layer was deposited on the textured pyramid-like SiNX film of p-type silicon solar-cells, as shown in the schematic view of Fig. 1(a), and it was confirmed that the as-synthesized Mn doped Cd0.5Zn0.5S/ZnS core/shell QDs had a Mn doped Cd0.5Zn0.5S core diameter of 6.83 nm and ZnS shell thickness of 2.40 nm, as shown in Fig. 1(b). It was also confirmed that the Mn2+ doped Cd0.5Zn0.5S/ZnS core/shell QDs, absorbed UV-visible region (250–450 nm in wavelength) and emitted yellow-orange visible region (583 nm in wavelength). For p−type silicon solar−cells coated with the QDs layer, in particular, it was observed that the p-type silicon solar-cells coated with 0.064M Mn2+ doped Cd0.5Zn0.5S/ZnS core/shell QDs demonstrated better photovoltaic performance. The JSC increased abruptly from 35.34 to 36.76 mA/cm2 at 0.3-wt% QDs concentration, and which was a 4.02% increase compared to the reference without the QDs layer. Finally, the PCE of 0.55 % in the solar-cell coated with Mn2+ doped QDs layer were achieved at the 0.3-wt% of core–shell QDs doped with 0.064 M, compared with those of solar-cells with uncoated QDs layers. These results indicate that the coating of Mn doped Cd0.5Zn0.5S/ZnS core/shell QDs on the SiNX film textured surface for p−type silicon solar−cells affect JSCdue to the energy−down−shift using energy-tuning-effect of the QDs.

* This work was financially supported by the Brain Korea 21 plus Project in 2016, Korea.

Reference

[1] Baek, S W. et al., Journal of

Materials Chemistry A2014.

[2] Baek, S W. et al., Phys. Chem. Chem. Phys.2014, 16, 18205-18210.

[3] Baek, S. W.; Shim, J. H.; Seung, H. M.; Lee, G. S.; Hong, J. P.; Lee, K. S.; Park, J. G. Nanoscale 2014.

[4]. Zeng, R.; Rutherford, M.; Xie, R.; Zou, B.; Peng, X. Chem. Mater. 2010, (22), 2107-2113.

Figure 1