A 14% efficient nonaqueous semiconductor/liquid junction solar cell

We describe the most efficient semiconductor/liquid junction solar cell reported to date. Under W-halogen (ELH) illumination, the device is a 14% efficient two-electrode solar cell fabricated from an n-type silicon photoanode in contact with a nonaqueous electrolyte solution. The cell′s central feature is an ultrathin electrolyte layer which simultaneously reduces losses which result from electrode polarization, electrolyte light absorption, and electrolyte resistance. The thin electrolyte layer also eliminates the need for forced convection of the redox couple and allows for precise control over the amount of water (and other electrolyte impurities) exposed to the semiconductor. After one month of continuous operation under ELH light at 100 mW/cm ², which corresponds to the passage of over 70 000 C/cm², thin-layer cells retained over 90% of their efficiency. In addition, when made with Wacker Silso cast polycrystalline Si, cells yield an efficiency of 9.8% under simulated AMl illumination. The thin-layer cells employ no external compensation yet surpass their corresponding experimental (three-electrode) predecessors in efficiency.