Open-Circuit-Voltage Improvement Mechanism of Perovskite Solar Cells Revealed by Operando Spin Observation.

Organic-inorganic hybrid perovskite solar cells have attracted much attention as important next-generation solar cells. Their solar cell performance is known to change during operation, but the root cause of the instability remains unclear. This report describes an investigation using electron spin resonance (ESR) to evaluate an improvement mechanism for the open-circuit voltage, VOC, of inverted perovskite solar cells at the initial stage of device operation. The ESR study revealed electron transfer at the interface from the perovskite layer to the hole-transport layer not only under dark conditions but also under light irradiation, where electrons are subsequently trapped in the hole-transport layer. An electron barrier is enhanced at the perovskite/hole-transport-layer interface, improving field-effect passivation at the interface. Thereby, the interface recombination velocity is reduced, and thus the VOC improves. These findings are crucially important for elucidating the mechanisms of device performance changes under operation. They reveal a relation between charge transfer and performance improvement, which is valuable for the further development of efficient perovskite solar cells.

Useful method to monitor the physiological effects of alcohol ingestion by combination of micro-integrated laser Doppler blood flow meter and arm-raising test.

Alcohol has a variety of effects on the human body, affecting both the sympathetic and parasympathetic nervous system. We examined the peripheral blood flow of alcohol drinkers using a micro-integrated laser Doppler blood flow meter (micro-electromechanical system blood flow sensor). An increased heart rate and blood flow was recorded at the earlobe after alcohol ingestion, and we observed strong correlation between blood flow, heart rate, and breath alcohol content in light drinkers; but not heavy drinkers. We also found that the amplitude of pulse waves measured at the fingertip during an arm-raising test significantly decreased on alcohol consumption, regardless of the individual's alcohol tolerance. Our micro-electromechanical system blood flow sensor successfully detected various physiological changes in peripheral blood circulation induced by alcohol consumption.