Deciphering Adverse Detrapped Hole Transfer in Hot‐Electron Photoelectric Conversion at Infrared Wavelengths

• Published in: Advanced materials (Weinheim) Vol. 35; no. 12; pp. e2210157 - n/a
• Main Authors: Yu, Yuanfang, Gao, Lei, Niu, Xianghong, Liu, Kaiyang, Li, Ruizhi, Yang, Dandan, Zeng, Haibo, Wang, Hui‐Qiong, Ni, Zhenhua, Lu, Junpeng
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 01.03.2023
• Subjects: Carrier density; Conversion; Degeneration; detrapped hole transfer; Electron transfer; Excitation; Hot electrons; hot‐electron photodetectors; Illumination; Infrared radiation; photoelectric conversion efficiency; Photoelectric effect; Photoelectric emission; Photoelectricity; Quantum efficiency; Screening; surface plasmon resonances; surface plasmon resonances; photoelectric conversion efficiency; detrapped hole transfer; hot-electron photodetectors
• ISSN: 0935-9648; 1521-4095
• DOI: 10.1002/adma.202210157

Hot‐carrier devices are promising alternatives for enabling path breaking photoelectric conversion. However, existing hot‐carrier devices suffer from low efficiencies, particularly in the infrared region, and ambiguous physical mechanisms. In this work, the competitive interfacial transfer mechanisms of detrapped holes and hot electrons in hot‐carrier devices are discovered. Through photocurrent polarity research and optical‐pump–THz‐probe (OPTP) spectroscopy, it is verified 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 two 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. Existing hot‐carrier devices suffer from low efficiencies, particularly in the infrared region, and ambiguous physical mechanisms. In this work, the competitive interfacial transfer mechanisms of detrapped holes and hot electrons in hot‐carrier devices are discovered. By eliminating the adverse detrapped‐hole transfer, the external quantum efficiency of a hot‐electron device can increase by over two orders of magnitude at 10 mW cm−2.