14 March 2016 Effective drift mobility approximation in multiple quantum-well solar cell
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Abstract
Multiple quantum well (MQW) solar cells have been explored as one promising next-generation solar cells toward high conversion efficiency. However, the dynamics of photogenerated carriers in MQWs are complicated, making it difficult to predict the device performance. Our purpose of this study is to investigate a model for the photocurrent component characteristics of MQW cells based on experimental findings. Using our proposed carrier time-of-flight technique, we have found that the carrier averaged drift velocity has linear dependence on the internal field regardless of complicated carrier cascade dynamics in MQW. This behavior is similar to carriers in bulk materials, allowing us to approximate the MQW region as a quasi-bulk material with specific effective drift mobility. With the effective drift mobility and equivalent material parameters such as effective density of states, the quasi-bulk approach reduces the device complexity, and the characteristics of such MQW cells can be simulated using the conventional drift-diffusion model. We have confirmed this model with experimentally obtained photocurrent characteristics. The simulation of carrier collection efficiency (CCE)—normalized photocurrent—based on the effective mobility approximation, or quasibulk approximation, agrees well with the experimental results when the carrier lifetime is set to be in the order of hundred nanoseconds. This simplified model enhances our understanding of the MQW cell operation and helps design the optimal structure for better performance.
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Kasidit Toprasertpong, Tomoyuki Inoue, Kentaroh Watanabe, Takashi Kita, Masakazu Sugiyama, Yoshiaki Nakano, "Effective drift mobility approximation in multiple quantum-well solar cell", Proc. SPIE 9743, Physics, Simulation, and Photonic Engineering of Photovoltaic Devices V, 974315 (14 March 2016); doi: 10.1117/12.2209611; https://doi.org/10.1117/12.2209611
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