Organohalide perovskite films are usually prepared with the solid-state reaction at a high temperature >= 100 degrees C, which causes the increase of non-radiative defects and decomposition of perovskite films. Here, we demonstrate it's feasible to prepare high-quality perovskite films with the solid-state reaction method even at a temperature of 75 degrees C, when enhanced by less-crystallized nanoporous PbI2 (ln-PbI2) films. The replacement of compact PbI2 (c-PbI2) by In-PbI2, results in a significant improvement of crystallinity of perovskite films, besides the elimination of remnant PbI2, As a result, In-PbI2 based perovskite solar cells display much higher power conversion efficiency (PCE) and better stability. Moreover, annealing duration was found to be critical for high PCE and was optimized as 60 min. Finally, with the optimal process, the champion device displayed a PCE of 13.8% and the average PCE reached 10.1% with a satisfactory deviation. Furthermore, we found annealing at high temperature (140 degrees C) led to a lower PCE compared with that annealed at 75 degrees C, because non-radiative defects increased significantly during high-temperature annealing. This work may open up a promising avenue for preparing high-quality perovskite films with the low-temperature solid-state reaction method, which is desirable for real application. 2017 Elsevier B.V. All rights reserved.