Ultraviolet-Filtering Luminescent Transparent Coatings for High-Performance PTB7-Th:ITIC–Based Organic Solar Cells

Joana Farinhas,Ana Charas,Alexandre M P Botas,Paulo S André,Rute A S Ferreira,Sandra F H Correia,Lianshe Fu

doi:10.3389/fnano.2021.635929

Abstract

Photovoltaic (PV) devices based on organic heterojunctions have recently achieved remarkable power conversion efficiency (PCE) values. However, photodegradation is often a cause of dramatic drops in device performance. The use of ultraviolet (UV)-absorbing luminescent downshifting (LDS) layers can be a mitigation strategy to simultaneously filter UV radiation reaching the device and reemit it with lower energy in the visible spectral range, matching the maximum spectral response of the PV cells and thus enabling the increase of the photocurrent generated by the cell. In this work, we report the use of a Eu3+-doped siliceous-based organic–inorganic hybrid as a coating on organic solar cells based on the PTB7-Th:ITIC bulk heterojunction with the purpose of increasing their performance. We found that the applied coatings yield a PCE enhancement of ∼22% (from 3.1 to 3.8%) in solar cells with spin-coated layers, compared with the bare solar cells, which is among the highest performance enhancements induced by plastic luminescent coatings.

Highlights

Photovoltaic (PV) solar cells based on solution-processed organic semiconductors, either polymers or small molecules, arranged in bulk heterojunctions (BHJ) as the photoactive layer, have recently exhibited remarkable performance in small-area devices, proving great promise as competitors of their well-established inorganic counterparts
Y6 belongs to a new class of non-fullerene acceptors (NFAs) based on a central core of fused aromatic rings linked to electron-deficient end Luminescent Downshifting Layers units, whose molecular design enables surpassing the drawbacks of the standard fullerene acceptors, PC60BM and PC70BM, by exhibiting broader absorption of the solar radiation
We investigate the effect of a di-ureasil organic–inorganic hybrid modified with Eu3+ luminescent downshifting (LDS) layer when applied over the light-incident surface of organic photovoltaic (OPV) cells of such a class, namely, with the PTB7-Th:ITIC BHJ

Summary

Introduction

Photovoltaic (PV) solar cells based on solution-processed organic semiconductors, either polymers or small molecules, arranged in bulk heterojunctions (BHJ) as the photoactive layer, have recently exhibited remarkable performance in small-area devices, proving great promise as competitors of their well-established inorganic counterparts. Organic photovoltaic (OPV) technology is especially attractive because low-cost deposition methods, such as roll-to-roll printing, can be employed in its manufacture, and semitransparent and light-weight modules can be fabricated over glass or curved plastic substrates. As for cells with NFAs, superior photoinduced intrinsic degradation was documented for devices with the efficient ITIC acceptor than for PC71BM-based counterparts (Doumon et al, 2019). One strategy to prevent intrinsic photoinduced device degradation consists of reducing the UV portion of the incident radiation in the device To test this possibility, Cha et al used radiation without UV to illuminate encapsulated devices with an efficient polymer:NFA BHJ made of PffBT4T-2OD:EH-IDTBR, and found superior performance stability (Cha et al, 2017). Other proposals used UV longpass filters with different cutoff wavelengths to illuminate OPV cells based on PTB7-Th:PCBM blends and obtained significant improvements in both open-circuit voltage (VOC) and shortcircuit current density (JSC) for filters cutting up to 400 nm (Liu et al, 2017)

Methods

Results

Conclusion