Sub-bandgap near-infrared photovoltaic response in Au/Al2O3/n-Si metal–insulator–semiconductor structure by plasmon-enhanced internal photoemission

Abstract

Silicon sub-bandgap near-infrared (NIR) (λ > 1100 nm) photovoltaic (PV) response by plasmon-enhanced internal photoemission was investigated. The Si sub-bandgap NIR PV response, which remains unexploited in Schottky junction-like solar cell device, was examined using nanometer sized Au/Al2O3/n-Si junction arrays. This kind of metal–insulator–semiconductor structure was similar in functionality to Schottky junction in NIR absorption, photo-induced charge separation and collection. It showed that NIR absorption increased steadily with increasing volume of Au nanoparticles (NPs) till a saturation was reached. Simulation results indicated the formation of localized surface plasmon on the surfaces of Au NPs, which was correlated well with the observed NIR absorption. On the other hand, the NIR PV response was found sensitive to the amount and size of Au NPs and thickness of Al2O3. Chemical and field-effect passivation of n-Si by using Al2O3 and SiO2 were used to optimize the NIR PV response. In the current configuration, the best PV conversion efficiency was 0.034% at λ = 1319 nm under illumination power of 0.1 W/cm2.

A Silicon Sub-Bandgap Near-Infrared Photodetector with High Detectivity Based on Textured Si/Au Nanoparticle Schottky Junctions Covered with Graphene Film

“…It is worth pointing out that the strong plasmonic effect of Au NPs was a critical factor leading to good responsivities [35][36][37]. In our previously reported work, the device fabricated with Au thin film showed responsivities lower than 1 mA/W [18]. Compared with the case of Au thin film, the localized surface plasmons generated by Au NPs could enhance the NIR absorption and localized electric field, which increased the number and kinetic energy of hot electrons, thus enhancing the photocurrent [24,38].…”

“…After annealing, Au NPs were formed on the textured Si surface, with sizes of 40.1 ± 25.9 nm. On the other hand, a small number of larger Au NPs, approximately 100 nm in size, appeared on the ridges of the Si pyramids, which could be more favorable for Au NP nucleation [18].…”

“…Following the formation of Au NPs, the NIR absorption of the textured Si/Au NP sample increased significantly to an average of about 70%. This enhanced absorption stemmed from the Au NPs, where localized surface plasmons (LSPs) were induced by incident NIR light, generating energetic hot electrons [7,18,24,25]. These hot electrons were primarily responsible for photodetection by forming a photoinduced current through the IPE process [26,27].…”

“…After annealing, Au NPs were formed on the textured Si surface, with sizes of 40.1 ± 25.9 nm. On the other hand, a small number of larger Au NPs, approximately 100 nm in size, appeared on the ridges of the Si pyramids, which could be more favorable for Au NP nucleation [18]. The absorption spectra of the textured Si, textured Si/Au NPs, and textured Si/Au NPs/Gr in the NIR wavelength range of 1200-1800 nm were measured, as shown in Figure 3.…”

“…To fabricate textured Si with pyramid structure, the Si wafer was etched in a solution of NaOH (Sinopharm Chemical Reagent Co., Ltd., Shanghai, China, 2 wt%), Na 2 SiO 3 (Aladdin, Shanghai, China, 2 wt%), and isopropyl alcohol (Sinopharm Chemical Reagent Co., Ltd., Shanghai, China, 7 vol%) at 80 • C for 25 min. Textured Si could enhance the light absorption through light trapping and simultaneously facilitate the subsequent formation of Si/Au NPs Schottky junctions [17,18]. The textured Si was then rinsed in deionized water and cleaned in a solution of H 2 O:H 2 O 2 (Sinopharm Chemical Reagent Co., Ltd., Shanghai, China, 30%):NH 3 (Sinopharm Chemical Reagent Co., Ltd., Shanghai, China, 25%) = 6:1:1 at 70 • C for 20 min and H 2 O:H 2 O 2 (30%):HCl (Sinopharm Chemical Reagent Co., Ltd., Shanghai, China, 36%) = 6:1:1 at 70 • C for 10 min in sequence.…”