Experimental demonstration of energy-transfer ratchet intermediate-band solar cell

A detailed balance calculation reveals an extremely high efficiency of 63.2% for intermediate-band solar cells (IBSCs) under maximum sunlight concentration. However, an actual IBSC device with an efficiency larger than the Shockley-Queisser (SQ) limit has so far not been reported. The main difficulties lie in realizing an efficient sequential two-photon absorption (STPA) which requires a sufficiently long lifetime intermediate state or intermediate band. In this article, we propose the concept of a ratchet type IBSC, utilizing a long lifetime of rare-earth ion luminescence centers in Erbium-doped GaAs. The temperature dependent differential external quantum efficiency reveals a significant STPA contribution originating from the Er3+ luminescence center. All the results were modeled and interpreted by integrating the ratchet effect with up-conversion along with a density functional theory (DFT) simulation. Our work demonstrates that the long lifetime energy-transfer mechanism in Er3+ centers contributes directly to the formation of a ratchet type IB. Intermediate band solar cell is a type of photovoltaic cell which includes additional narrow band states which allow absorption of low energy below-bandgap photons that might otherwise be transmitted from the host material. Here, the authors report a type of ratchet intermediate band solar cell prepared by doping GaAs with erbium and investigate the underlying energy transfer mechanisms.

Automated summary

This paper introduces the concept of a novel "ratchet type" intermediate band solar cell, utilizing long-lifetime rare-earth ion luminescence centers in Erbium-doped GaAs. Temperature-dependent differential external quantum efficiency studies show a significant contribution from Er3+ luminescence centers in this system. Simulation results indicate that the long lifetime energy transfer mechanism of Er3+ ions plays a key role in the formation of the "ratchet type" intermediate band solar cell.