Nanoporous Polymer Reflectors for Organic Solar Cells

Abstract

Due to their high transparency, electrodes fabricated from conductive polymers are often implemented in semitransparent organic solar cells. Opaque solar cells usually employ metal back electrodes with high reflectivity for best photon confinement in the light‐harvesting layer. Herein, a bilayer back electrode comprising conductive polymers and nanofoamed poly(methyl methacrylate) (PMMA) is investigated, the latter of which creates diffuse reflection of the incoming light. By tuning the thickness of the nanofoamed PMMA layer, absorption and transmission of the solar cells can be tailored from opaque to vastly transparent. Due to its diffusive character, this versatile electrode enhances the light absorption in the wavelength regimes with lower absorption coefficient. The solar cells are particularly suited for deployment in frosted window applications.

Recent Progress in Light‐Scattering Porous Polymers and Their Applications

“…By varying the thickness of pristine polymer film, different reflectance can be obtained, which is desired for the light management of semi‐transparent OSCs. [ 36 ] At last, a 50 µm‐thick foamed polymer film can increase the PCE of OSCs from 5.9% to 6.8%, comparable with the highly reflective silver electrode. Detailed characterizations showed that the PCE enhancement was attributed to the increased light absorption in the low‐absorbing spectral range and further improved photocurrent in the OSCs.…”

“…Reproduced with permission. [ 36 ] Copyright 2021, The Authors, published by Wiley‐VCH. Porous polymers are also excellent candidates applied in the passive daytime radiative cooling [ 37 ] and radiative cooling fabrics.…”

“…d) Schematic diagram of OSC integrated with a nanoporous polymer film on the rear side as a diffuse light reflector. Reproduced with permission [36]. Copyright 2021, The Authors, published by Wiley-VCH.…”

Status report on emerging photovoltaics

“…Dielectric scatterer based on titania can be used to redirect light in stacked homo- 212 and hetero- 213 tandem devices based on semitransparent 212 – 215 OPV devices, converting the semitransparent OPV to an opaque OPV. With white paper 216 or nanoporous polymers, 217 as well as a microstructured retroreflector, 218 light harvesting is improved.…”

Porous organic polymers in solar cells

“…Besides the enhancement in charge transport layers, the incorporation in the electrode has also been recently demonstrated a promising approach to replace commonly used metals. Yu et al 160 showcased a highly reflective nanoporous polymer incorporated back electrode with thickness-dependent opacity and transmission. Through CO 2 diffusion, the nanofoamed PMMA presents an excellent reflectance profile compared to the silver electrode in the Vis-NIR region.…”