Highly efficient p-i-n perovskite solar cells employing a flat and thick CH(3)NH(3)Pbl(3) film and a thin PCBM film are fabricated by the solution-process at low temperature. Through attainment of optimized PCBM thickness and insertion of the LW interlayer, the unit cell shows 14.1% of overall power conversion efficiency (PCE) with a J(sc) of 20.7 mA cm(-2), a V-oc of 0.866 V, and a FF of 78.3% under AM 1.5G 100 mW cm(-2) conditions, while a larger area 10 cell serially connected module (10 x 10 cm(2)) shows an 8.7% PCE. These PCE values are the highest reported to date for the planar perovskite-PCBM solar cells.