Transition metal carbide (Mo2C) and carbon nanotubes (CNTs) have been used to modify the hole transport layers (HTLs) in perovskite solar cells (PSCs) and photodetectors due to their high metallic conductivity, superior charge extraction probability, tunable work function, and high reliability. Here, for the first time, Mo2C, CNTs, and a Mo2C-CNT hybrid were blended with a PEDOT:PSS HTL in an ITO/HTL/CH3NH3PbI3/PCBM/ LiF/Al device architecture. The power conversion efficiency of the resulting PSC improved to 11.98% with the use of Mo2C-CNT@PEDOT:PSS HTL compared to the pure PEDOT:PSS (9.17%), Mo2C@PEDOT:PSS (9.82%) and CNT@PEDOT:PSS (10.61%) HTLs. The PSC performance of device prototypes with different loadings (1, 1.5, and 2 wt%) of the Mo2C@CNT nanocomposite in the HTL was also examined. The prepared Mo2C-CNT@ PEDOT:PSS HTL-based device was then employed as X-ray photodetector, achieving a maximum sensitivity of 3.56 mA/Gy·cm2. Our findings illustrate the potential for the use of MXene-CNT nanocomposites with a perovskite layer to enhance the efficacy of solar cells and photodetectors.