Improving stability and photoluminescence of CsPbBr3 quantum dots/CMC polymer composite for optoelectronics application

Cesium lead halide perovskite quantum dots (PQDs) are the most promising materials for optoelectronic application due to their high photoluminescence quantum yield. However, the poor stability of these PQDs is the major bottleneck towards commercial applications. There have been several strategies to improve the stability of these PQDs which includes PQDs-polymer composite with limited success. In this article we have synthesized CsPbBr₃ quantum dots- Carboxymethylcellulose (CMC) composite for the first time to improve the optoelectronic properties as well as stability of these PQDs compared to pure PQDs. Photoluminescence (PL) is significantly improved while the degradation becomes slower than pure PQDs. There is a slight blue shift of ∼8 nm in the absorption spectrum of PQDs/CMC composite indicating almost negligible bandgap alteration. This is also confirmed by the high-resolution transmission electron microscopy analysis. However, 78 meV increase in quasi-fermi level splitting (QFLS) is observed in PQD/CMC optimum composite indicating reduced non-radiative recombination due to defect passivation. However, excess CMC beyond 0.3 mol% in PQDs reduces the PL intensity possibly due to increased defect states or the structural changes at higher CMC concentrations. This can be also confirmed by analysing the x-ray diffraction peak at (112) which disappears at higher concentration of CMC.