A novel sequential layer-by-layer sub-100 °C vacuum-sublimation method to fabricate planar-type organometal halide perovskite solar cells is developed. Very uniform and highly crystalline perovskite thin films with 100% surface coverage are produced. The cells attain maximum and average efficiencies up to 15.4% and 14%, respectively. This low- temperature, all-vacuum process is suitable for a wide variety of rigid and flexible applications. As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized for online delivery, but are not copy-edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.