Solar cells based on crystalline silicon (Si) offer high efficiency but they are expensive partially because they require ultra-clean furnaces, pure precursors and high temperatures. The alternative approach using lowtemperature processable organic-semiconductors is potentially cheaper, but organic solar cells are not very efficient. Here, we explore if single walled carbon nanotubes (SWNTs) can be integrated with Si to form hybrid SWNT/Si solar cells that are both efficient and low-cost. We have developed two scalable solution processes for fabricating SWNT thin films that are not only highly transparent and conductive, but also mechanically robust and morphologically smooth. Room temperature deposition of as-made SWNT thin films on Si results in SWNT/Si hybrid solar cells. The key design rules and post-processing to achieve higher power conversion efficiencies are discussed and experimentally demonstrated. Using the prescribed design rules and post-processing, SWNT/Si hybrid solar cells with a fill factor of 73.8%, ideality factor of 1.08 as well as overall dry cell power conversion efficiency of 11.5% are demonstrated.