Quantum dot sensitized solar cells using semiconductor nano-particles have attracted much interest because they are expected to have a high efficiency and a low manufacturing cost. Narrow band-gap semiconductors such as CdS, PbS, and CdSe are employed as sensitizers, and they transfer photo-generated electrons in them to large band-gap semiconductors such as TiO2 under light excitation. Our interest has been concerned with quantum dot solar cells using Si coumpound nano-particles because Si is abundant and has little toxicity. We have succeeded in producing Si nano-particles of a narrow size dispersion using a multi-hollow discharge plasma CVD method [1], and have applied them to Si quantum dot sensitized solar cells [2]. In our CVD system, discharges were sustained in 8 small holes of 5 mm in diameter at SiH4 and H2 flow rates of 2 and 448 sccm. Si nano-particles were nucleated, grew in SiH₄/H₂ plasma produced inside small holes, and were transported to the downstream region by neutral gas flow. We also performed surface nitridation of Si nano-partciles to terminate dangling bond of the surface. Our experiments clearly demonstrated advantages of nitridation of Si nano-particles on the device performance; the short circuit current of Si QDs sensitized solar cells showed 1.3 times higher value by the nitridation and a photon to current conversion efficiency (PCE) achieved a high value of 40% at short wavelength of 350nm [3, 4]. Moreover, quantum dot sensitized solar cells using FeSi nanoparticles show better performance than those using Si nanoparticles. We will compare characteristics of three kinds of quantum dot sensitized solar cells using Si, Si/SiN core shell, and FeSi nanoparticles and discuss relationship between optical and electrical properties of the nanoparticles and the device performance.