We have overcome two drawbacks involved in series-connected double-junction (S-2J) and triple-junction (S-3J) photovoltaic cells to compose monolithic modules of artificial photosynthesis consisting of directly connected photovoltaic cells and electrolyzers of the same size. One is current mismatching among the subcells under solar spectrum variation. The other is inefficient utilization of high-energy photons that can generate sufficiently high voltage to promote the target reaction, caused by consumption of two or three photons for extracting a single electron regardless of the photon energies. This arises from the predetermined operating voltage, contrasting to no restriction of the output voltage for solar cells combined with power conditioners. In a series/parallel-connected triple-junction (S/P-3J) photovoltaic cell, the series-connected middle and bottom cells are connected with the top cell in parallel. High-energy photons absorbed in the top cell are efficiently utilized because the photoexcited electrons are directly extracted. Although relative intensities of high-energy photons in the measured solar spectra changes remarkably, the top cell is free from the current matching restriction. On the other hand, current matching between the middle and bottom cells approximately holds, because solar spectrum in the relevant range changes only slightly. Consequently, the S/P-3J significantly improves solar-to-chemical conversion efficiency (ηSTC) and is more advantageous on overcast days owing to the spectral robustness. Using the state-of-the-art electrolyzers, ηSTC = 32%−26% of H2 production by water splitting is estimated on fine and overcast days. CO2 reduction to CO proceeds with ηSTC = 30%−25%. These values are higher than those for the S-2J by 3%−9%.

中文翻译：

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用于人工光合作用的光谱稳定的串联/并联三结光伏电池

我们克服了串联双结（S-2J）和三结（S-3J）光伏电池的两个缺点，组成了由直接连接的光伏电池和相同尺寸的电解槽组成的人工光合作用单片模块。一种是太阳光谱变化下子电池之间的电流不匹配。另一个是高能光子的低效利用，可以产生足够高的电压来促进目标反应，这是由于无论光子能量如何，都需要消耗两个或三个光子来提取单个电子。这是由预定的工作电压引起的，与结合功率调节器的太阳能电池的输出电压没有限制形成对比。在串联/并联三结（S/P-3J）光伏电池中，串联的中间和底部电池与顶部电池并联。由于直接提取了光激发电子，因此可以有效利用顶部电池中吸收的高能光子。虽然测得的太阳光谱中高能光子的相对强度变化显着，但顶部电池不受电流匹配限制。另一方面，中间电池和底部电池之间的电流匹配大致成立，因为相关范围内的太阳光谱变化很小。因此，S/P-3J 显着提高了太阳能化学转化效率 (ηSTC)，并且由于光谱稳健性，在阴天时更有利。使用最先进的电解槽，在晴天和阴天估计 ηSTC = 32%−26% 的水分解 H2 产量。CO2 还原为 CO，ηSTC = 30%−25%。这些值比 S-2J 的值高 3%-9%。