NOVELTY - A buffer layer is obtained by applying a charge-transporting varnish containing a charge-transporting substance comprising an oligoaniline compound (I), an electron-accepting dopant substance and an organic solvent on a positive electrode of the organic thin film solar cell or thin film on the positive electrode, and baking the resultant product at 135 degrees C or less.    USE - Buffer layer e.g. anode buffer layer is used for organic thin-film solar cell (all claimed).    ADVANTAGE - The lightweight buffer layer having excellent heat resistance and flexibility, high-hole transportability and low hygroscopicity is economically manufactured. The organic thin-film solar cell comprising the buffer layer has high photoelectric conversion efficiency, favorable reproducibility and excellent durability.    DETAILED DESCRIPTION - A buffer layer is obtained by applying a charge-transporting varnish containing a charge-transporting substance comprising an oligoaniline compound of formula (I), an electron-accepting dopant substance and an organic solvent on a positive electrode of the organic thin film solar cell or thin film on the positive electrode, and baking the resultant product at 135 degrees C or less.    R 1-R 19=H, halo, nitro, cyano, amino, hydroxy, thiol, phosphoric acid group, sulfonic acid group, carboxy, aldehyde, 1-20C alkyl optionally substituted by Z 1, 2-20C alkenyl or 2-20C alkynyl, or 6-20C aryl or 2-20C heteroaryl (both optionally substituted by Z 2), -NHY 1, -NY 2Y 3, -OY 4, -SY 5, -SO 3Y 6, -C(O)OY 7 or -C(O)Y 8;    Y 1-Y 8=1-20C alkyl optionally substituted by Z 1, 2-20C alkenyl or 2-20C alkynyl, or 6-20C aryl or 2-20C heteroaryl (both optionally substituted by Z 2);    Z 1=halo, nitro, cyano, hydroxy, thiol, amino, phosphoric acid group, sulfonic acid group, carboxy, aldehyde, or 6-20C aryl or 2-20C heteroaryl (both optionally substituted by Z 3);    Z 2=halo, nitro, cyano, hydroxy, thiol, amino, phosphoric acid group, sulfonic acid group, carboxy, aldehyde, 1-20C alkyl optionally substituted by Z 3, 2-20C alkenyl or 2-20C alkynyl;    Z 3=halo, nitro, cyano, hydroxy, thiol, amino, phosphoric acid group, sulfonic acid group, carboxy or aldehyde;    m,n=1 or more;and    or m+2n=20 or less.    INDEPENDENT CLAIMS are included for the following:    (1) organic thin-film solar cell, which comprises the buffer layer, and active layer; and    (2) manufacture of buffer layer.