Deciphering Adverse Detrapped Hole Transfer in Hot-electron Photoelectric Conversion at Infrared Wavelengths.

Hot-carrier devices are promising alternatives for enabling pathbreaking photoelectric conversion. However, existing hot-carrier devices suffer from low efficiencies, particularly in the infrared region, and ambiguous physical mechanisms. We discover the competitive interfacial transfer mechanisms of detrapped holes and hot electrons in hot-carrier devices. Through photocurrent polarity research and optical-pump THz-probe (OPTP) spectroscopy, we verify that detrapped hole transfer (DHT) and hot electron transfer (HET) dominate the low- and high-density excitation responses, respectively. The photocurrent ratio assigned to DHT and HET increases from 6.6% to over 1133.3% as the illumination intensity decreases. DHT induces severe degeneration of the external quantum efficiency (EQE), especially at low illumination intensities. The EQE of a hot-electron device can theoretically increase by over 2 orders of magnitude at 10 mW/cm 2 through DHT elimination. The OPTP results show that competitive transfer arises from the carrier oscillation type and carrier density-related Coulomb screening. The screening intensity determines the excitation weight and hot-electron cooling scenes and thereby the transfer dynamics. This article is protected by copyright. All rights reserved.