Light harvesting enhancement toward low IPCE region of semitransparent polymer solar cells via one-dimensional photonic crystal reflectors

In this study, we demonstrate a light harvesting method to achieve efficient semitransparent polymer solar cells (STPSCs) based on PCDTBT: PC70BM by employing one-dimensional photonic crystals (1DPCs) as reflector. The 1DPCs were constructed by N pairs of WO3/LiF, a pair means a combination of WO3 and LiF, including a layer of WO3 film and a layer of LiF film. By optimizing the number of pairs, a 1DPC with high reflectance region (400-500 nm), which is exactly matched with the weak region of the (incident photon-to-electron conversion) IPCE spectrum of the reference STPSC is obtained. In contrast, the excellent STPSC with 8 pairs of 1DPC exhibited a high efficiency about 4.84% and hold an average transmittance of 25.4% in the visible range (400-700 nm). (C) 2014 Elsevier B.V. All rights reserved.