We report the performance improvement of organic solar cell by addition of an n-type chemical doping layer in organic bulk heterojunction device. The power conversion efficiency (PCE) of P3HT and PCBM-71 based polymer solar cells increases by adding a mixture of TCNQ (7,7,8,8-tetracyanoquinodimethane) and LCV (Leucocrystal violet) between active layer and cathode electrode. The PCE of the cell increases by 14% compared to the control cell with Al-only cathode electrode. The device with an organic n-doped layer shows the J(SC) of 8.88 mA/cm(2), V(OC) of 0.51 V. FF of 60.1%, and thus the PCE of 2.72% under AM1.5 illumination of 100 mW/cm(2). Crown Copyright (C) 2011 Published by Elsevier B.V. All rights reserved.