Regimes of current transport mechanisms in CdS/CdTe solar cells
Regimes of current transport mechanisms in CdS/CdTe solar cells
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DOI：
10.1088/1361-6641/ab23b5
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发表时间：
2019-06
影响因子：
1.9
通讯作者：
H. Bayhan;E. T. Dağkaldıran;J. Major;K. Durose;M. Bayhan
中科院分区：
文献类型：
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作者：
H. Bayhan;E. T. Dağkaldıran;J. Major;K. Durose;M. Bayhan
正向偏置复合（电流传输）机制已被评估为薄膜太阳能电池和相关的间隙陷阱水平。在这里，CdTe/CdS器件被选为现代薄膜太阳能电池的典型示例，并且使用具有一系列设计变量的一组器件，以揭示可能限制电流传输的全部行为。实验的电流-电压-温度数据集进行了比较的数学模型的运输，并在间隙陷阱进行了评估，热导纳谱。电流传输机制的操作上的温度-电压图。确定了三个制度：在“中间”电压，行为是温度依赖性。从300 K下降到240 K，热激活的肖克利-里德-霍尔复合介导的0.38 eV的陷阱（VCD）占主导地位的运输。在200和240 K之间的运输是热激活的，但低于200 K的机制变得占主导地位的隧道辅助界面复合。在“低”电压下（并且对于在T < 200 K下测量的所有电压下的所有器件），带间复合是经由通过间隙状态的多步隧穿。在高电压下，正向电流由背肖特基接触对处于反向偏置的CdTe的众所周知的限制效应主导。电流传输行为也与n-CdS的厚度和氯化镉的处理条件，这两者都是至关重要的设备性能。
Forward bias recombination (current transport) mechanisms have been evaluated for thin film solar cells and correlated to the in-gap trap levels present. Here CdTe/CdS devices were chosen as an archetypal example of a modern thin film solar cell, and a set of devices with a range of design variables was used in order to reveal the full range of behaviours that may operate to limit current transport. Experimental current–voltage–temperature datasets were compared to mathematical models of transport, and the in-gap traps were evaluated by thermal admittance spectroscopy. The current transport mechanisms operating are presented on a temperature–voltage diagram. Three regimes were identified: at ‘intermediate’ voltages, the behaviour was temperature dependent. From 300 K down to 240 K, thermally activated Shockley Read Hall recombination mediated by a 0.38 eV trap (VCd) dominated the transport. Between 200 and 240 K the transport was thermally activated but below 200 K the mechanism became dominated by tunnel assisted interface recombination. At ‘low’ voltages (and for all devices at all voltages when measured at T < 200 K) band to band recombination is via multi-step tunnelling through in-gap states. At high voltage, the forward current is dominated by the well-known limiting effect of the back Schottky contact to the CdTe which is in reverse bias. The current transport behaviour is also correlated with the n-CdS thickness and CdCl2 processing conditions, both of which are critical to device performance.