Colloidal quantum dots (CQDs) solar cells are less efficient because of the carrier recombination within the material. The electron and hole transport layers have high impact on the performance of CQDs based solar cells which makes its investigation a very important component of the development of the more efficient devices. In this work, we have tried performance optimization in tetrabutyl ammonium iodide capped lead sulfide (PbS) CQDs (PbS-TBAI) as absorber layers based solar cells by incorporating different hole transport layers (HTLs) to achieve better power conversion efficiency (PCE) in different device architectures by SCAPS—1D numerical simulation software. It was observed from the simulation that the ITO/TiO2/PbS-TBAI/HTL/Au device architecture shows higher power conversion efficiency as compared to the conventional experimentally realized device architecture of ITO/TiO2/PbS-TBAI/PbS-EDT/HTL/Au. The influence of interface defect density (IDD) at the interface TiO2/PbS-TBAI has also been studied where IDD is varied from 1 × 1013cm−2to 1 × 1018cm−2while keeping the rest of the device parameters intact. The result shows a noteworthy reduction in the PV performance of the device at higher IDD. This modelled device structure provides a new direction toward the experimental realization in high efficiency PbS QDs solar cells.