Flexible ITO‐Free Organic Photovoltaics on Ultra‐Thin Flexible Glass Substrates with High Efficiency and Improved Stability

Abstract

The ability for organic solar cells to be conformable and bendable enables them to be used in a broad range of applications. Indium tin oxide (ITO) or PEDOT:PSS on plastic substrates such as poly(ethylene terephthalate) or poly(ethylene napthalate) (PET or PEN) have been used for transparent conductive electrodes (TCEs) for flexible devices. However, ITO is brittle and when used on flexible substrates is prone to cracking, and the acidity of PEDOT:PSS can lead to corrosion of the ester‐based plastic substrates and cause device degradation. In this work, TCEs based on modified high‐conductivity PEDOT:PSS on 100 μm‐thick flexible glass substrates are used as the anode for organic solar cells. The optimized PEDOT:PSS TCE anode on flexible glass has a sheet resistance of ≈30 Ω/sq and a transmission of ≈77% at 550 nm, with a broad transmission window between 300 and 800 nm. The best PEDOT:PSS on flexible glass‐based organic solar cell has a power conversion efficiency (PCE) of 8.0%, which is higher than devices comprising ITO or PEDOT:PSS on PEN, which have PCEs of 6.4% and 5.8%, respectively. It is also found that the ultra‐thin glass devices can be scaled, with 1.6 cm2 flexible cells having an efficiency of 5.2%.

Recent progress in organic solar cells (Part II device engineering)

“…However, some researchers found that the PEDOT:PSS with weak acidity may also lead to the device degradation during the storage. When the acid component PSS was removed to a certain extent by treating it with methanol or formic acid, the storage life time of the related device was effectively extended [147].…”

Flexible solar and thermal energy conversion devices: Organic photovoltaics (OPVs), organic thermoelectric generators (OTEGs) and hybrid PV-TEG systems

“…Recently, Wang et al used flexible glass substrates (100 μm thick) to fabricate ITO-free OSC based on a BQR: PC 71 BM donor-acceptor system and achieved a PCE of 8% [351]. Nevertheless, Xiong et al has reported flexible OSC fabricated on an ITO coated PET substrate, using water processable PEIE as an ETL and PTB7-Th: IEICO-4F as the donor-acceptor system, demonstrating a high PCE of 12.5%.…”

Progress in Upscaling Organic Photovoltaic Devices

“…In a 2019 study, Wang et al [301] prepared TCEs based on high conductivity PEDOT:PSS PH 1000 on ultrathin (100 µm-thick) flexible glass substrates, with optimized TCEs exhibiting a R S of ≈30 Ω⋅□ −1 and a transmittance of ≈77% at 550 nm, with a broad transparency window observed between 300 and 800 nm. OPV cells with active area 1.6 cm 2 and with the structure glass/ PEDOT:PSS PH1000/MoOx/BQR:PC 71 BM/Ca/Al achieved a PCE of 5.2% (compared to 8.0% for devices with small area of 0.2 cm 2 ).…”