Electronic Properties and Optical Absorption of Amorphous Superlattices

太阳能电池光伏效率的提高是通过提高光吸收效率和电子-空穴对的提取效率来实现的。前者与非晶态半导体超晶格的层宽有关，而后者受吸收光谱中指数尾部的宽度控制。考虑到这种情况，本研究的目的是从理论上阐明非晶态半导体超晶格的层宽变化对吸收光谱中指数尾部宽度的影响。我们的研究结果总结如下：(A)即使当对角项的涨落与井层宽度无关时，随着井层宽度的减小，对角项涨落的影响也变得更加严重。结果是，吸收光谱中指数尾部的宽度增加，电子…(B)即使当对角线项的波动以及井层宽度的变化与井层本身的宽度无关时，对相邻井层之间的隧道几率的波动的影响也随着井层宽度的减小而变得更加显著。因此，吸收光谱中指数尾部的宽度增加。(C)在现实的物理系统中，对角项的涨落不能独立于势垒层的宽度。实际上，随着井层宽度的减小，井层宽度的变化更加明显。这是因为井层宽度的减小导致层间效应和能级的增加。因此，对角项不可避免地受到影响。hs导致层间效应和层间效应的增加。因此，对角项不可避免地会受到影响。(D)从这些结果来看，可以通过提高光吸收效率和电子-空穴提取效率来提高光伏效率。这可以通过i来实现。减少井层宽度的变化，安地。最小化势垒和井层之间的层间效应，从而最大限度地减少井层中的拓扑无序。较少

The increase of the photovoltaic efficiency in solar cells is realized by improving both the optical absorption efficiency and the extraction efficiency of electron-hole pairs. The former is related to the layer widths of an amorphous semiconductor superlattice, while the latter is governed by the width of the exponential tail in the absorption spectra. With this situation in mind, the purpose of the present research is to clarify theoretically the influence of the variation in the layer widths of an amorphous semiconductor superlattice on the width of the exponential tail in the absorption spectra. The results obtained from our study are summarized as follows.(a) Even when the fluctuations of the diagonal terms are fixed independent of the widths of well layers, the effects from the fluctuations of the diagonal terms become more serious according as the widths of well layers decrease. As a result, the width of the exponential tail in the absorption spectra increases and the electrons … More in the tail region become more localized.(b) Even when the fluctuations fo the diagonal terms as well as the variations in the widths of well layers are fixed independent of the widths themselves of well layers, the influence on the fluctuations of the tunneling probabilities between the adjacent well layers become more marked according as the widths of well layers are reduced. As a consequence, the width of the exponential tail in the absorption spectra increases.(c) In realistic physical systems, the fluctuations of the diagonal terms cannot be independent of the widths of well layers. In fact, the variations in the widths of well layers becomes more distinguished according to the decrease of well-layer widths. This is because the decrease of well-layer widths causes the increase both the interlayer effects and in the levels. As a consequence, the diagonal terms are inevitably influenced.hs causes the increase both the interlayer effects and in the levels. As a consequence, the diagonal terms are inevitablly influenced.(d) From these results, the photovoltaic efficiency can be increased by improving both the optical absorption efficiency and the electron-hole extraction efficiency. This can be achieved byi. reducing the variations in the widths of well layers, andii. minimizing the interlayer effects between a barrier and well layer, thus decreasing the topological disorder in well layers as much as possible. Less