Band alignment and conversion efficiency in Si/Ge type-II quantum dot intermediate band solar cells
Band alignment and conversion efficiency in Si/Ge type-II quantum dot intermediate band solar cells
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DOI：
10.1088/0957-4484/18/40/405401
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发表时间：
2007-10-10
期刊：
影响因子：
3.5
通讯作者：
Kechiyants, H. M.
中科院分区：
文献类型：
--
作者：
Kechiantz, A. M.;Kocharyan, L. M.;Kechiyants, H. M.
中间带（IB）太阳能电池（SC）的概念提供了实现63%转换效率器件的希望。分析了量子点（QD）IB SC中的II型能带排列对上述百分比的影响，并讨论了Ge/Si系统用于制造II型QD IB SC的潜力。另外，太阳光浓度的增加导致量子点周围势垒的升高，当S-x浓度接近700时，Ge/Si系统中的势垒高度可达到λ（L）= 0.2eV，这是一个有意义的结果.此外，太阳光浓度的增加导致准费米能级从量子点的束缚态中分离，也导致量子点中复合活性的降低。在中等浓度下，量子点的双光子吸收迅速增加，并在复合过程中占主导地位。作为量子点的贡献，在II型量子点IB SC的光电流和暗电流进行评估，它示出，相比于传统的硅SC，II型锗量子点IB硅SC可以产生约25%的高光电流和转换效率。
The concept of the intermediate band (IB) solar cells (SC) offers the promise of achieving 63% conversion efficiency devices. The effect of the type II band alignment in the quantum dot (QD) IB SCs on the above percentage is analyzed and the potential of the Ge/Si system for fabrication of the type II QD IB SC is discussed. Also, it is shown that the increase of the sunlight concentration leads to the rise of the potential barrier around QDs and the concentration of S-x approximate to 700 can induce the epsilon(L) = 0.2 eV height barrier in the Ge/Si system, making this a significant result. Furthermore, the increase of the sunlight concentration leads to the separation of the quasi-Fermi levels from the confined states and also leads to the decrease of the recombination activity in QDs. The two-photon absorption in QDs increases rapidly and dominates over recombination at the moderate concentration. As the contributions of QDs to both the photo- and dark currents in the type II QD IB SC are evaluated it is shown that, compared to the conventional Si SCs, the type II Ge QD IB Si SCs can generate about 25% higher photocurrent and conversion efficiency.