Two-step photon up-conversion solar cells

• Published in: Nature communications Vol. 8; no. 1; p. 14962
• Main Authors: Asahi, Shigeo, Teranishi, Haruyuki, Kusaki, Kazuki, Kaizu, Toshiyuki, Kita, Takashi
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 06.04.2017; Nature Publishing Group; Nature Portfolio
• Subjects: 639/4077/909/4101/4096/946; 639/624/1075/401; 639/624/399/1017; Energy; Humanities and Social Sciences; Interfaces; multidisciplinary; Quantum dots; Science; Science (multidisciplinary); Semiconductors
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms14962

Reducing the transmission loss for below-gap photons is a straightforward way to break the limit of the energy-conversion efficiency of solar cells (SCs). The up-conversion of below-gap photons is very promising for generating additional photocurrent. Here we propose a two-step photon up-conversion SC with a hetero-interface comprising different bandgaps of Al 0.3 Ga 0.7 As and GaAs. The below-gap photons for Al 0.3 Ga 0.7 As excite GaAs and generate electrons at the hetero-interface. The accumulated electrons at the hetero-interface are pumped upwards into the Al 0.3 Ga 0.7 As barrier by below-gap photons for GaAs. Efficient two-step photon up-conversion is achieved by introducing InAs quantum dots at the hetero-interface. We observe not only a dramatic increase in the additional photocurrent, which exceeds the reported values by approximately two orders of magnitude, but also an increase in the photovoltage. These results suggest that the two-step photon up-conversion SC has a high potential for implementation in the next-generation high-efficiency SCs. Harvesting incident photons with energy below the bandgap may lead to highly efficient solar cells. By introducing InAs quantum dots at the hetero-interface, Asahi et al . achieve efficient two step photon up-conversion resulting in additional photocurrent and very high external quantum efficiency.