From tandem solar cell we expect a wide absorption range due to different bandgaps of the subcells, higher open circuit voltage V_oc and finally better photo conversion efficiency $\eta$ than single junction solar cell. The main drawback of it is a current limitation i.e. the short circuit current $J_{\mathit{sc}}$ of whole structure is equal to smaller $J_{\mathit{sc}}$ of both subcells. However, even two subcells with very good photovoltaic performance do not guarantee the correct operation of tandem solar cell. The tunnel junction plays a crucial role on tandem devices as it has to provide low loss electrical and optical connection between top and bottom subcells.

Within this paper we present two subcells: top GaAs based, bottom InGaAsN based with good photovoltaic performance and InGaAs tunnel diode used for InGaAsN/GaAs tandem solar cell construction. We compare reference devices with monolithic tandem cell and conclude about tunnel junction failure based on both dark and illuminated J-V characteristics of the InGaAsN/GaAs final device. Based on detailed analysis of tandem performance we propose two most likely effects responsible for tunnel junction induced deterioration of tandem solar cell performance.

对于串联太阳能电池，由于子电池的不同带隙，更高的开路电压V _oc和最终更好的光电转换效率，我们预计吸收范围宽$\eta$比单结太阳能电池 它的主要缺点是电流限制，即短路电流${Ĵ}_{\mathit{SC}}$ 整体结构等于较小 ${Ĵ}_{\mathit{SC}}$两个子单元。然而，即使两个具有非常好的光伏性能的子电池也不能保证串联太阳能电池的正确运行。隧道结在串联设备上起着至关重要的作用，因为它必须在顶部和底部子电池之间提供低损耗的电气和光学连接。

在本文中，我们介绍了两个子电池：基于顶部GaAs，具有良好光伏性能的底部InGaAsN和用于InGaAsN / GaAs串联太阳能电池构造的InGaAs隧道二极管。我们将参考器件与整体串联电池进行了比较，并基于InGaAsN / GaAs最终器件的黑暗和光照JV特性总结了隧道结故障。在详细分析串联性能的基础上，我们提出了两种最有可能造成隧道结诱发串联太阳能电池性能下降的效应。