Abstract
Thin layers of silicon nanocrystals (SiNC) in oxide matrix with optimized parameters are fabricated by the plasma-enhanced chemical vapor deposition. These materials with SiNC sizes of about 4.5 nm and the SiO2 barrier thickness of 3 nm reveal external quantum yield (QY) close to 50% which is near to the best chemically synthetized colloidal SiNC. Internal QY is determined using the Purcell effect, i.e. modifying radiative decay rate by the proximity of a high index medium in a special wedge-shape sample. For the first time we performed these experiments at variable temperatures. The complete optical characterization and knowledge of both internal and external QY allow to estimate the spectral distribution of the dark and bright NC populations within the SiNC ensemble. We show that SiNCs emitting at around 1.2–1.3 eV are mostly bright with internal QY reaching 80% at room temperature and being reduced by thermally activated non-radiative processes (below 100 K internal QY approaches 100%). The mechanisms of non-radiative decay are discussed based on their temperature dependence.
Highlights
Silicon nanocrystals (SiNC) embedded in silicon dioxide (SiO2) have been shown to provide high photoluminescence (PL) quantum yield (QY) of the order of 20% which is size tunable in the spectral region from orange to near infrared (NIR), i.e. about 650–1100 nm[1]
The probability of spontaneous decay of an emitter is defined by the local density of optical states (LDOS) that can be tuned by putting an emitter in a cavity
We show that silicon nanocrystals (SiNC) emitting at around 1.2–1.3 eV are mostly bright with IQY reaching 80% at room temperature and being reduced by thermally activated non-radiative processes
Summary
Silicon nanocrystals (SiNC) embedded in silicon dioxide (SiO2) have been shown to provide high photoluminescence (PL) quantum yield (QY) of the order of 20% which is size tunable in the spectral region from orange to near infrared (NIR), i.e. about 650–1100 nm[1]. Such quality can be potentially exploited to provide photon conversion in lighting and photovoltaic devices[2]. IQY is determined using the Purcell effect, i.e. modifying radiative decay rate by the proximity of a high index medium in a special wedge-shape sample. The mechanisms of non-radiative decay are discussed based on their temperature dependence
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