Performance enhancement of organic/inorganic hybrid solar cells by improving the optical absorption of polymer

The performance of the polymer/ZnO nanorod hybrid solar cells based on poly(3-hexylthiophene) and methanofullerenes is improved with the enhanced optical absorption by increasing the thickness of the photoactive layer and introducing a solution-processed interlayer. The dependence of the optical absorption on the thickness of the photoactive layer is studied as a function of the spin-coating rate. With the slower spin-coating rate, the photoactive layer is thicker, and the polymer chains have longer time to self-organize and more effectively infiltrate into ZnO nanorod spacing. In addition, a solution-processed fullerene interlayer is introduced to modify the ZnO nanorod surface. With this interlayer, the optical absorption of the photoactive layer increases due to the better ordering of the photoactive layer. Our investigations show that the power conversion efficiency (PCE) is improved from 1.6% to 2.6% with the thickness of the photoactive layer from 240 nm to 350 nm by slowing the spin coating rate of the photoactive layer. Moreover, the PCE is also improved by the fullerene interlayer. The slow-drying method and the solution-processed fullerene interlayer both improve the crystallinity of the polymer and light harvesting. © 2009 SPIE.