Unambiguously layer by layer (LBL) assembly of graphene quantum dots (GQDs) and dye (GQDs/dye) on TiO2 photoanode is the traditional and straightforward approach in the fabrication of graphene quantum dot-sensitized solar cells (QDSSCs). Unfortunately, limited light absorption and low affinity of GQDs to TiO2 surface shadow the advantages of LBL and constrains its practical application. Herein, a new strategy of mixture configuration (GQDs+dye) was investigated. A distinctive nanoporous honeycomb hexagonal carbon network of GQDs was found with fewer defects single crystalline structure, and an average size of 9.87 nm was produced from cellulose. Experimental results demonstrated that LBL exhibited the highest efficiency of 16.76 % under low illumination but a lower efficiency (1.43%) than the mixture method (2.91%) under standard light. The increased Jsc (5.075 mA/cm2) and high charge collection efficiency (0.96) in the mixture sample indicated enhanced electron collection at TiO2. The less -OH groups on TiO2 provides a good surface intact of GQDs and N719. In addition to that, the high surface potential (33.47 mV) of the premixed sample restricted the photogenerated electrons to go into a deep state, reducing back electron transfer. Therefore, mixture assembly of co-sensitization is an effective approach for light-harvesting in QDSSC.