Solar cells using living micro-organisms often require the help of a redox mediator, a small molecule which carries the electrons from inside the organisms to the electrode. Ideally the mediator is able to cross biological membranes to access the source of electrons, without causing damage. The diffusion rate across membranes, reduction rate inside the micro-organism, and the absence of toxicity are key parameters. Here we use modeling, fit of fluorescence and electrochemical experimental data, and simulation to quantify the reaction rates of the main processes involved in the case of the micro-alga Chlamydomonas reinhardtii, in interaction with the redox mediator 2,6-dichloro-1,4-benzoquinone. We found that the photo-induced reduction inside algae is not the limiting process, but in contrast 10 times faster than the process of electron consumption at the electrode. The maximum current limitation is due to the slow outflow of the mediator out of algae: the molecule has a tendency to get trapped inside because of its lipophilicity. Additionally, it has an important toxicity, and we find that its mode of action is likely to cause a quasi-exponential decay of the number of active photosynthetic chains. This is consistent with known side effects of quinones (oxidative stress, electrophilic behaviour).

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微生物太阳能电池的基本机制：建模如何提供帮助

使用活微生物的太阳能电池通常需要氧化还原介体的帮助，氧化还原介体是一种将电子从生物内部传递到电极的小分子。理想地，介体能够穿过生物膜以进入电子源，而不会造成损害。跨膜的扩散速率，微生物内部的还原速率以及无毒性是关键参数。在这里，我们使用建模，荧光和电化学实验数据的拟合以及模拟来量化涉及微藻莱茵衣藻的主要过程的反应速率。与氧化还原介体2,6-二氯-1,4-苯醌相互作用。我们发现，藻类内部的光诱导还原不是限制性过程，相反，它比电极上电子消耗过程快10倍。最大电流限制是由于介体从藻类中缓慢流出：该分子由于其亲脂性而倾向于被困在内部。此外，它具有重要的毒性，我们发现它的作用方式很可能引起活性光合链数量的准指数衰减。这与醌的已知副作用（氧化应激，亲电行为）一致。