To become self-sustaining, human habitats in extreme environments such as the moon and Mars will require bioregenerative life support systems (BLSS) involving controlled environment agriculture (CEA) technology. CEA is an enabling technology for growing plants in an enclosed space with optimal conditions, and plants facilitate human survival in space. Just as on Earth, plants provide important ecosystem services, including atmospheric revitalization, water purification, and food production. To demonstrate the feasibility of plants to provide all the oxygen and water as well as half the caloric requirements of one astronaut, the Prototype Mars-Lunar Greenhouse (MLGH) was developed as BLSS in which plants could be grown hydroponically. Previous experiments in the MLGH approached these goals, but plant productivity needed to be improved to satisfy life-support requirements. Plant growth is rate-limited by quantity and quality of light radiation; thus, a novel agricultural application of colloidal semiconductor nanocrystals, or quantum dots (QDs), was investigated to optimize the spectral quality provided to the plants. Two types of CuInS2/ZnS core-shell QDs were manufactured and embedded as fluorophores into plastic nanocomposite films. The QDs absorbed ultraviolet and blue light and exhibited peak emissions at wavelengths of either 600 nm (Orange) or 660 nm (Red) within the photosynthetically active radiation range. For 28 days, these QD films and a QD-free, polyethylene control film were positioned between solar spectrum-mimicking lamps and lettuce (Lactuca sativa L. cv. ‘Outredgeous’ red romaine) grown under uniform environmental conditions in a laboratory setting. Compared with the lettuce grown under the control film, crop yield increases under the Orange and Red films were respectively observed: edible dry mass (13% and 9%), edible fresh mass (11% and 11%), and total leaf area (8% and 13%). These crop yield enhancements demonstrate the potential for spectral quality optimization with QDs in controlled environments.