Controlled Synthesis of Long-Wavelength Multicolor-Emitting Carbon Dots for Highly Efficient Tandem Luminescent Solar Concentrators

Long-wavelength multicolor emission and high photoluminescence quantum yields (PLQYs) play a key role in carbon dot (CD)-based luminescent solar concentrators (LSCs). Herein, long-wavelength multicolor-emitting CDs with high PLQYs had been synthesized by one-step solvothermal process of phenylenediamine (PD) isomers (m-, o-, p-PDs) in the presence of lignin. Relying on the introduction of lignin, green (G), yellow (Y), and red (R) emissive CDs without excitation wavelength dependence could be achieved. The R, Y, G CDs showed clearly red shift effect in PL emission spectra, compared to the control CDs samples (Rc, Yc, Gc CDs) only based on PD isomers as precursors. The PL red shift probably resulted from the size effect of CDs. Remarkably, the R, Y, G CDs with high PLQYs (15.01, 41.52, and 7.60%) had been achieved owing to their long PL lifetimes, which is also higher than that of control Rc, Yc, Gc CDs samples (PLQYs of 12.66, 38.32, and 3.48%). Moreover, the tandem LSCs based on the R, Y, G CDs had further been demonstrated. The external optical efficiency (ηopt) and power conversion efficiency (η) of LSCs had been enhanced greatly up to 4.03 and 2.92%, respectively, compared to that of LSCs based on the control CDs LSCs (only have 3.76 and 2.66%).