Abstract
Defects play a pivotal role in the device performance of a photocatalytic, light-emitting, or photovoltaic system. Herein, graphitic carbon nitride (g-C3N4) nanosheets are prepared at different calcination temperatures, and the evolution of defects in the system is studied by positron annihilation spectroscopy (PAS) and photoluminescence (PL) spectroscopy. Steady-state PL spectra show that free and defect-bound excitonic emission peaked at 2.78, 2.58, and 2.38 eV are dominant with above-band-gap excitation. Time-resolved PL studies reveal a significant enhancement of excitonic lifetime from 17.4 ns for free exciton to 27.4 ns in case of defect-bound exciton. We provide a direct correlation between the defects observed by PAS and those of the excitonic lifetime found from PL studies. Below-band-gap excitation activates defect emission, and it is characterized by a short carrier lifetime (∼0.14 ns). An excitation power-dependent PL study with 405 nm laser shows a progressive red shift and narrowing of the e...
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