Transparent polymer solar cells employing a layered light-trapping architecture

Abstract

Organic solar cells have unique properties that make them very attractive as a renewable energy source. Of particular interest are semi-transparent cells, which have the potential to be integrated into building façades yet not completely block light. However, making organic cells transparent limits the metal electrode thickness to a few nanometres, drastically reducing its reflectivity and the device photon-harvesting capacity. Here, we propose and implement an ad hoc path for light-harvesting recovery to bring the photon-to-charge conversion up to almost 80% that of its opaque counterpart. We report semi-transparent PTB7:PC 71 BM cells that exhibit 30% visible light transmission and 5.6% power conversion efficiency. Non-periodic photonic crystals are used to trap near-infrared and near-ultraviolet photons. By modifying the layer structure it is possible to tune the device colour without significantly altering cell performance.

Semi-transparent polymer solar cells

“…transmission weighted by the product of the human eye photopic spectral response with illumination from the white standard illuminant CIE-D65, 41 organic technology offers the most promising solution.…”

“…[82][83][84][85] The second approach to increase transparency in the visible spectrum and to limit the loss in PCE is the incorporation of multilayer anti-reflection coatings for the visible or Bragg reflectors to help to trap the near UV and NIR. 41,42,[86][87][88][89][90] The combination of both may further improve the balance between transparency and PCE. But an optimal performance is achieved when the multilayer structure is a nonperiodic structure designed ad hoc.…”

“…But an optimal performance is achieved when the multilayer structure is a nonperiodic structure designed ad hoc. 41 In the latter case, an inverse integration design must be used to specifically determine each layer thickness for the extinction coefficient of the absorber layers, the rest of the materials used in the electrodes and buffer layers, and the architecture of the device as a whole. The last category we will discuss consists of enclosing the active layer in a Fabry-Perot type cavity formed by the two metallic semi-transparent electrodes.…”

Role of Vertical Segregation in Semitransparent Organic Photovoltaics

“…Using all the knowledge learnt from OPVs during the last decade semitransparent devices with conversion efficiencies (PCE) as high as of 5.4 % in single layer 7 or 7 % in tandem configuration 8 have been obtained with average transmission of 30%. Alternatively, PCE of 6.4% have been achieved with a maximum transmission of 51% at 550 nm in the tandem configuration.…”

4-Terminal Tandem Photovoltaic Cell Using Two Layers of PTB7:PC71BM for Optimal Light Absorption

“…Another very interesting feature of the organic layer in a PV cell is its partial colorless transparency to visible light. 3 Both, flexibility and a colorless transparency are key features for an optimal building integrated PV that only the organic technology may be able to offer.…”