Solution-processed inverted polymer solar cells using chemical bath deposited CdS films as electron collecting layer

We report the fabrication of a solution-processed cadmium sulfide (CdS) film and its application in inverted polymer solar cells (PSCs). The CdS film is formed by a chemical bath deposition (CBD) process and exhibits an n-type semiconducting property. An efficient inverted PSC is fabricated using a CBD-grown CdS film as the electron collecting layer (ECL), which is inserted between the indium tin oxide (ITO) cathode and the polymer bulk heterojunction active layer. The experimental results reveal that the cell response parameters depend critically on the deposition procedures in terms of bath temperature, deposition time and annealing temperature. A two-fold increase in the overall power conversion efficiency of inverted PSCs is realized with the optimization of CBD-grown CdS film properties through the deposition for 2 h at 50 °C and the annealing treatment at 200 °C. The simple and low-cost deposition method of CdS films is promising for the fabrication of hybrid PSCs.