The photoelectron-hole recombination in silver halide crystals is the major process responsible for the lack of conversion of light into the latent image. In order to favor the escape of electrons from recombination and to enhance the effective quantum yield, photographic emulsions are doped with Chini-type platinum carbonyl clusters [Pt₃(CO)₆]_n^2–(n = 6 − 9) which are known to behave as electron donors or acceptors. An increase in sensitivity of silver bromide of Δlog(I × t_exp) = 0.5 without fogging compared to undoped crystals is obtained through this process for a relative concentration of 5 × 10^–5 Pt atoms per silver ion and an intermediate intensity. The attenuation of HIRF (Δlog(I × t_exp) = 0.6 at high intensity) and mostly of LIRF (Δlog(I × t_exp) = 1.0 at low intensity) confirms that the doping contributes to lowering the electron-hole recombination and indicates that clusters act mainly as hole scavengers. The doping by clusters induces a sensitivity increase of Δlog(I × t_exp) = 0.26 for (S + Au) sensitized emulsions but causes no change in ultrasensitive formate doped emulsions. Similar results are obtained in AgCl crystals.