In order to achieve standalone wearable and foldable electronics, the integration of high efficiency stretchable energy harvesting devices is essential. Here, we demonstrate the development of ultra-stretchable solar cells based on monocrystalline silicon with interdigitated back contacts and high efficiency (19%). The stretchability of the photovoltaic devices is achieved by encapsulating the originally rigid solar cell with an elastomer followed by applying a deep-reactive ion etching based corrugation technique. Two different corrugation patterns are investigated: linear and triangular. The results show that, due to the ability of the triangular designs to relieve the generated strain, the cells can be stretched by up to twice their original size with no noticeable decline in the initial performance.