Realization of Foldable Polymer Solar Cells Using Ultrathin Cellophane Substrates and ZnO/Ag/ZnO Transparent Electrodes

Abstract

Foldable solar cells have attracted increasing attention for portable and wearable applications. The challenge to achieve foldability is free from the formation of cracks under large strain. Our mechanical simulations suggests that a reduction in substrate thickness from 150 to 25 μm is a means to mitigate the strain in polymer solar cells under folding with extremely small curvature radius of sub‐millimeter. The polymer solar cells are experimentally prepared on ultrathin 25 μm cellophane substrates with ZnO/ultrathin Ag/ZnO (OMO) transparent electrodes, instead of conventional ITO, composing a typical device structure, cellophane/OMO/ZnO/PTB7‐Th:PC71BM/MoO3/Al. The solar cells exhibit a power conversion efficiency of 5.94% and a power weight ratio of 2.11 W g−1. After folding the solar cells for 35 cycles, the conversion efficiency still maintained 92% of the initial value, which is mainly ascribed to the synergistic effects of ultrathin substrates and the OMO electrodes, as inferred from the stable resistance of the cellophane/ZnO/ultrathin Ag/ZnO even after 50 folding cycles. This work paves the way toward realizing superior foldability not only in solar cells, but also in other optoelectronic devices.

Highly Foldable and Efficient Paper‐Based Perovskite Solar Cells

“…the reported organic solar cells retained 50% of initial PCE after 10 folding cycles, and CuInSe 2 solar cells only worked after 5 folding cycles. In our previous report, foldable polymer solar cells were realized, which retained 92% of the initial PCE after 35 folding cycles . Herein, we further realized foldable PSCs, which remained over 84% of the initial PCE even after 50 folding cycles.…”

“…Further increasing folding cycle resulted in the formation of cracks in ITO and CuInSe 2 absorber layers. In our previous work, strategies of using ultrathin substrate to relieve strain as well as foldable oxide/ultrathin silver/oxide (OMO) to replace brittle ITO were implemented, as a result, polymer solar cells could work after 35 folding cycles when folding the device outside the substrate with angle of 180 0 . While the 5.94% power conversion efficiency (PCE) of polymer solar cells on paper was far from practical application.…”

“…Many kinds of solar cells, such as organic, dye‐sensitized, thin film silicon, CuInSe 2 , and perovskite solar cells (PSCs), have been fabricated on paper. So far only a few reports paid attention to the foldability of paper‐based solar cells.…”

Printed Solar Cells and Energy Storage Devices on Paper Substrates

“…N-type (i.e. those that extract electrons) DMD electrodes such as TiOx(40nm)/Ag(10 nm)/TiOx(40nm) [57] or ZnO(40nm)/Ag(12nm)/ZnO(40nm) [106] had a resistance:trasmittance ratio of only 2/:70% (when measured between 400-600 nm) or 7.2/:81.7% (when measured between 400-800nm), respectively. TiOx/Ag/TiOx electrode was used as bottom window electrode on nanopaper for perovskite solar cells (PSC) while ZnO/Ag/ZnO was successfully implemented in organic solar cell.…”

“…[70] In this work, a nanocomposite paper was developed by introducing a rigid percolating network of tunicate cellulose nanocrystals (TCNC) in a soft 0- Record PCE has been achieved by using a spin-coated PTB7-Th:PC71BM blend as the active layer for paper-based OPV. Li et al [106]…”