Temperature Dependence of Ideality Factors in Organic Solar Cells and the Relation to Radiative Efficiency
Temperature Dependence of Ideality Factors in Organic Solar Cells and the Relation to Radiative Efficiency
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DOI：
10.1002/aenm.201502230
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发表时间：
2016-05
影响因子：
27.8
通讯作者：
Kristofer Tvingstedt;C. Deibel
中科院分区：
文献类型：
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作者：
Kristofer Tvingstedt;C. Deibel
理想因子的值和温度依赖性提供了太阳能电池中主要重组途径的重要信息。本研究提出了在不同温度下，在大电流密度下，精确确定典型有机光伏电池（OPV）理想因数的实验结果。值得注意的是，标准的暗I-V曲线与基于短路电流密度(jsc) -开路电压（voc）对的评估结果有很大的偏差。这是由于在暗I-V测量中施加的外部电压不能代表内部化学势，特别是在较低温度下。互补电致发光测量证明，太阳能电池发光能力的电流密度依赖性与串联无电阻理想因数有较好的相关性。对于所研究的OPV器件，理想因子很低，且温度依赖性很弱。确定理想因子的SC-V OC方法进一步可以很好地估计活化能以及重组电流前因子j00。研究结果表明，主要的OPV非辐射复合机制不是先前报道的自由载流子与捕获载流子以指数密度的尾态复合。
The value and temperature dependence of the ideality factor provides essential information about the dominant recombination route in solar cells. This study presents experimental results of accurate ideality factor determination for representative organic photovoltaic cells (OPV) evaluated at different temperatures over a large current density regime. It is noted that standard dark I–V curves strongly deviate from those obtained by evaluations based on short circuit current density (J SC)–open circuit voltage (V OC) pairs. This is attributed to the applied external voltage in a dark I–V measurement not being representative of internal chemical potential, particularly at lower temperatures. Complementary electroluminescence measurements attest that the current density dependence of the ability of the solar cell to emit light is better correlated to the series resistance free ideality factor. For the studied set of OPV devices it is observed that the ideality factors are quite low, and with very weak temperature dependence. The J SC–V OC method to determine ideality factors further allows good estimates of activation energies as well as recombination current prefactors J 00. The findings imply that the principal OPV non‐radiative recombination mechanism is not recombination of free carriers with trapped carriers in an exponential density of tail states as previously reported.