The aim of CHEOPS is to develop very low-cost but highly performing photovoltaic (PV) devices based on the emerging perovskite (PK) technology. At lab scale (<0.5cm2), PK energy conversion was rapidly advanced to efficiencies >20%. But only few attempts at upscaling have been made, yielding significantly reduced efficiencies <9% on aperture area. In addition, the very question about material stability and reliable measurement procedures are still debated.CHEOPS will now scale up the lab results to single junction modules manufactured in a pre-production environment while maintaining high efficiencies (>14% stable for aperture area in modules >15x15cm2). This will demonstrate the potential of PK as a very low-cost technology (target <0.3€/Wp) well suited for building-integrated PV.In parallel, CHEOPS will develop materials and processes to achieve very high efficiency (>29% on 2x2cm2 cells) at low cost (target <0.4€/Wp) using a tandem configuration with a crystalline silicon heterojunction cell.CHEOPS will also perform a sustainability assessment from a life-cycle perspective to anticipate potential risks for the technology (including business, technological, environmental, social & political risks). CHEOPS will establish a quantified future development roadmap as well as protocols for stability testing and for reliable measurements.CHEOPS partners cover the whole value added chain: key PK researchers, groups with track records of scaling up high efficiency and tandem cell developments, specialised technology and service providers as well as SMEs and industry partners with already strong IP portfolios, ready to exploit the CHEOPS results. Transferring the results to other growing industry sectors such as lighting or organic large area electronics will additionally benefit European industry.In summary, CHEOPS will decisively advance the potentially game-changing PK technology towards the market and will thus help to face the energy challenge in Europe and beyond.