Ultra-flexible semitransparent organic photovoltaics

Abstract

Ultra-flexible organic photovoltaics (OPVs) are promising candidates for next-generation power sources owing to their low weight, transparency, and flexibility. However, obtaining ultra-flexibility under extreme repetitive mechanical stress while maintaining optical transparency remains challenging because of the intrinsic brittleness of transparent electrodes. Here, we introduce strain-durable ultra-flexible semitransparent OPVs with a thickness below 2 μm. The conformal surface coverage of nanoscale thin metal electrodes (< 10 nm) is achieved, resulting in extremely low flexural rigidity and high strain durability. In-depth optical and electrical analyses on ultrathin metal electrodes showed that the devices maintain over 73% of their initial efficiency after 1000 cycles of repetitive compression and release at 66% compressive strain, and the average visible light transmittances remain higher than 30%. To our knowledge, this is the first systematical study on mechanical behaviors of strain-durable ultra-flexible ST-OPVs through precise adjustment of each ultrathin electrode thickness toward the emergence of next-generation flexible power sources.

Semitransparent Organic Photovoltaic Devices: Interface/Bulk Properties and Stability Issues

“…In order to facilitate efficient charge separation and transport, additional layers between the active material and the electrodes can be used, acting as electron transport layers (ETL) and hole transporting layer (HTL) [11]. Despite the performances of ST-OSCs in terms of efficiencies and stability being still not comparable with the standard Si technology, organic-based systems are extremely advantageous as they can be easily fabricated on a large scale by low-cost solution processes methods [12], even on flexible substrates [13,14]. Since the overall performances of ST-OSCs strongly depend on the properties of the transparent electrode and of the active layer, much effort has been recently dedicated to the attempt of realizing efficient ST-OSCs by a proper selection and engineering of the materials in the multilayer architecture.…”

High-efficiency ultrathin flexible organic solar cells with a bilayer hole transport layer

“…Currently, the PCE of bottom-illuminated ultrathin organic solar cells is around 16% and various methods are employed to improve the efficiency of ultrathin devices. 34–36 Ge and co-workers developed a ternary ultrathin OSC based on the D18-Cl:Y6:PC 71 BM blend, achieving an efficiency of 15.5%. 37 Zhou et al introduced a Zn 2+ chelating polyethyleneimine (referred to as PEI-Zn) interlayer, which led to ultrathin OSCs achieving a PCE of 15.8%.…”