In this paper an improved design for thin film solar cells is proposed to enhance conversion efficiency. This proposed structure includes two pairs of additional contact to the reversed bias of absorber and buffer layers, directly. The purpose of additional electrodes is to control the carrier distribution in the active region of device. This idea has been implemented on the fabricated Copper indium gallium selenide solar cell with the record efficiency of 22%. The simulations show an improvement of 2% in the conversion efficiency is obtained by direct application of reverse biasing on the absorber and buffer layer. The increase of short circuit current more than 3 mA/cm2 is responsible for the improved performance. The open circuit voltage and fill factor of cell can also be increased by the controlling reverse bias.