In situ grown p-nc-Si:H/a-SiCx:H quantum dot superlattice has been prepared by RF-PECVD at a low temperature of 150 degrees C using layer by layer technique. This preparation method for fabricating superlattice allows controlling the properties of Si quantum dots in potential wells and the characteristics of potential barrier without subsequent annealing treatment, which is fully compatible with thin film Si technologies. High resolution transmission electron microscopy investigations confirm the superlattice structure of silicon quantum dots (similar to 2 nm diameter) separated by a-SiCx:H matrix (2-3 nm thickness) with several periods. Strong room-temperature photoluminescence and the blue-shift of the PL peak position with increasing barrier height are indicative of quantum confinement effects. Applying p-nc-Si:H/a-SiCx:H superlattice as window layers, high open circuit voltage (> 0.99 V) was achieved for n-i-p type a-Si:H single junction solar cells. (C) 2014 Elsevier B.V. All rights reserved.