Owing to its high mobility and low sintering temperature, ZnO is a promising electron-transporting layer for flexible and tandem applications of perovskite solar cells. However, ZnO inevitably triggers the degradation of perovskite materials. Such degradation can be inhibited when ZnO films with improved stoichiometry and minimized defects are used. In this work, a high efficiency with substantial stability of ZnO-based perovskite solar cells is achieved using a high-working pressure sputtering technique. The high-working-pressure sputtering process can produce higher quality ZnO films with fewer surface defects compared with conventional sputtering or sol-gel ZnO solution processes. A power conversion efficiency of 17.3\% is recorded. In addition, the stability of these devices is significantly higher than that of the conventional ZnO-based perovskite solar cells. This work showcases that ZnO can be a good candidate for the electron-transporting layer in perovskite solar cells, particularly for flexible and tandem applications when the right sputtering conditions are used.