Hajjiah Ali, Parmouneh Fahad, Hadipour Afshin, Jaysankar Manoj, Aernouts Tom
Electrical Engineering Department, College of Engineering and Petroleum, Kuwait University, Safat 13113, Kuwait.
Photovoltaics Department, Thin-Film PV Group, Imec, Partner in Solliance and Energyville, Thor Park 8320, 3600 Genk, Belgium.
Materials (Basel). 2018 Dec 17;11(12):2570. doi: 10.3390/ma11122570.
Mechanical stacking of a thin film perovskite-based solar cell on top of crystalline Si (cSi) solar cell has recently attracted a lot of attention as it is considered a viable route to overcome the limitations of cSi single junction power conversion efficiency. Effective light management is however crucial to minimize reflection or parasitic absorption losses in either the top cell or in the light in-coupling of the transmitted light to the bottom sub-cell. The study here is focused on calculating an optimum performance of a four-terminal mechanically stacked tandem structure by varying the optical property and thickness of the spacer between top and bottom sub-cells. The impact of the nature of the spacer material, with its refractive index and absorption coefficient, as well as the thickness of that layer is used as variables in the optical simulation. The optical simulation is done by using the transfer matrix-method (TMM) on a stack of a semi-transparent perovskite solar cell (top cell) mounted on top of a cSi interdigitated back contact (IBC) solar cell (bottom cell). Two types of perovskite absorber material are considered, with very similar optical properties. The total internal and external short circuit current (J) losses for the semitransparent perovskite top cell as a function of the different optical spacers (material and thickness) are calculated. While selecting the optical spacer materials, J for both silicon (bottom cell) and perovskite (top cell) were considered with the aim to optimize the stack for maximum overall short circuit current. From these simulations, it was found that this optimum in our four-terminal tandem occurred at a thickness of the optical spacer of 160 nm for a material with refractive index = 1.25. At this optimum, with a combination of selected semi-transparent perovskite top cell, the simulated maximum overall short circuit current (J) equals to 34.31 mA/cm². As a result, the four-terminal perovskite/cSi multi-junction solar cell exhibits a power conversion efficiency (PCE) of 25.26%, as the sum of the perovskite top cell PCE = 16.50% and the bottom IBC cSi cell PCE = 8.75%. This accounts for an improvement of more than 2% absolute when compared to the stand-alone IBC cSi solar cell with 23.2% efficiency.
最近，在晶体硅（cSi）太阳能电池顶部机械堆叠基于钙钛矿的薄膜太阳能电池引起了广泛关注，因为它被认为是克服cSi单结功率转换效率限制的可行途径。然而，有效的光管理对于最小化顶部电池中的反射或寄生吸收损失，或者将透射光耦合到底部子电池中的光损失至关重要。本研究的重点是通过改变顶部和底部子电池之间间隔层的光学性质和厚度，计算四端机械堆叠串联结构的最佳性能。间隔层材料的性质及其折射率和吸收系数，以及该层的厚度的影响，被用作光学模拟中的变量。光学模拟是通过对安装在cSi叉指背接触（IBC）太阳能电池（底部电池）顶部的半透明钙钛矿太阳能电池（顶部电池）堆叠使用传输矩阵法（TMM）来完成的。考虑了两种光学性质非常相似的钙钛矿吸收材料。计算了半透明钙钛矿顶部电池的总内部和外部短路电流（J）损失与不同光学间隔层（材料和厚度）的函数关系。在选择光学间隔层材料时，考虑了硅（底部电池）和钙钛矿（顶部电池）的J，目的是优化堆叠结构以获得最大的总短路电流。从这些模拟中发现，对于折射率为1.25的材料，我们的四端串联结构的最佳值出现在光学间隔层厚度为160nm时。在这个最佳值下，结合选定的半透明钙钛矿顶部电池，模拟的最大总短路电流（J）等于34.31 mA/cm²。结果，四端钙钛矿/cSi多结太阳能电池的功率转换效率（PCE）为25.26%，其中钙钛矿顶部电池PCE = 16.50%，底部IBC cSi电池PCE = 8.75%。与效率为23.2%的独立IBC cSi太阳能电池相比，这意味着绝对效率提高了超过2%。
