We demonstrate the efficiency enhancement and efficient hole extraction achieved by undoped Si nanocrystals (NCs) and p-type Si (p-Si) NCs in solution-processed bulk-heterojunction (BHJ) organic solar cells (OSCs) and planar-heterojunction (PHJ) perovskite solar cells (PrSCs). We observed that the surface coverage of Si–NCs on the substrate significantly affected the photovoltaic performance of the BHJ OSCs and PHJ PrSCs. The undoped Si NCs and p-Si NCs enhanced the power conversion efficiencies (PCEs) of the BHJ OSCs by ∼6% and ∼11%, respectively, and those of PHJ PrSCs by ∼22% and ∼23%, correspondingly, compared with the PCEs of devices without Si NCs. The p-Si NCs had a highest occupied molecular orbital (HOMO) energy level ∼0.16 eV higher than that of undoped Si NCs and showed better balances with the HOMO energy levels of the PTB7-Th and MAPbI₃ perovskite materials, achieving an increase in the hole mobility of the BHJ system, and thus demonstrating their key role as hole-extracting materials.