In classical DSCs, photons are absorbed by a Ru-based dye (N-719) with a bandgap of ~1.6 eV. This means any photons with wavelength longer than 775 nm will not be absorbed, representing a large portion of the solar spectrum. Upconversion is one approach to mitigate these losses. The process takes two or more lower energy photons (infrared) and converts them to a single higher energy photon (visible). Lanthanide doped optical materials are ideal for upconversion, with NaYF₄ doped with Yb³⁺/Er³⁺ known to be one of the most efficient upconverters. Thus we decided to investigate to what extent such upconversion materials can be utilized to enhance light harvesting and hence the photon conversion efficiency (PCE) of the DSC. For this investigation we focus on liquid-DSCs as case study trying to optimize the upconverter’s green light output that is known to best match with the absorption spectrum of N-719 dye. To this end first we synthesized via a citrate-modified hydrothermal process β-NaYF₄:Yb³⁺,Er³⁺ crystals of different shape and size that were subsequently annealed to optimize their UC efficiency (and green/red light output) before they were cast via paste screening as external or internal layers in a classical DSC configuration. While the external cast layer yielded enhanced PCE response the same was not true for the internal cast layer of UC crystals. This prompted us to engineer NaYF₄:Yb³⁺,Er³⁺@TiO₂ nanocomposites by controlled titanium dioxide coating of citrate-modified β- NaYF₄:Yb³⁺,Er³⁺ nanocrystals of ~300 nm in size and employed them as internal light harvesting layer in DSC fabrication. The NIR-to-Vis upconversion response of the as-prepared nanocomposites was enhanced by 2 orders of magnitude increase in the upconversion luminescence as a result of annealing effects induced by the thermal processing steps involved in DSC fabrication. In addition, the TiO₂ coating was found to suppress the β to α phase transition in the NaYF₄ thereby maximizing the upconversion response. The as-prepared upconversion crystals as well as 2 types of nanocomposite materials were integrated as internal light-harvesting layers and the PV parameters of the UC-incorporating DSCs were characterized. By ensuring the β- NaYF₄:Yb³⁺,Er³⁺ crystals are fully coated by TiO₂ (“core@shell” configuration), their integration into the DSC was optimized, resulting in 16% relative increase in PCE over the control devices.  The obtained performance results are probed by EIS analysis and their implications as to the potential role of upconversion in boosting the efficiency of DSCs or OPVs is discussed.