Directed Vertical Diffusion of Photovoltaic Active Layer Components into Porous ZnO‐Based Cathode Buffer Layers

Abstract

Cathode buffer layers (CBLs) can effectively further the efficiency of polymer solar cells (PSCs), after optimization of the active layer. Hidden between the active layer and cathode of the inverted PSC device configuration is the critical yet often unattended vertical diffusion of the active layer components across CBL. Here, a novel methodology of contrast variation with neutron and anomalous X-ray reflectivity to map the multicomponent depth compositions of inverted PSCs, covering from the active layer surface down to the bottom of the ZnO-based CBL, is developed. Uniquely revealed for a high-performance model PSC are the often overlooked porosity distributions of the ZnO-based CBL and the differential diffusions of the polymer PTB7-Th and fullerene derivative PC BM of the active layer into the CBL. Interface modification of the ZnO-based CBL with fullerene derivative PCBEOH for size-selective nanochannels can selectively improve the diffusion of PC BM more than that of the polymer. The deeper penetration of PC BM establishes a gradient distribution of fullerene derivatives over the ZnO/PCBE-OH CBL, resulting in markedly improved electron mobility and device efficiency of the inverted PSC. The result suggests a new CBL design concept of progressive matching of the conduction bands.

Conjugated Polyelectrolyte Blend with Polyethyleneimine Ethoxylated for Thickness-Insensitive Electron Injection Layers in Organic Light-Emitting Devices

“…It is considered that electron injection is difficult in such devices with the inverted layer stacking order. However, interspaces in ZnO NP films existed, and EIL materials could reach the F8BT/ZnO interface through the interspaces during EIL coating . The EIL materials at the F8BT/ZnO interface facilitated electron injection from ZnO to F8BT.…”

“…However, interspaces in ZnO NP films existed, and EIL materials could reach the F8BT/ZnO interface through the interspaces during EIL coating. 37 The EIL materials at the F8BT/ZnO interface facilitated electron injection from ZnO to F8BT. Then, we tested the driving stabilities of the devices with ZnO NPs/PEIE, ZnO NPs/PEIE:30 wt % PFN-Br, and ZnO/NPs PEIE:50 wt % PFN-Br at a constant current density of 25 mA/cm 2 .…”

MXene-Integrated Metal Oxide Transparent Photovoltaics and Self-Powered Photodetectors

“…Wide-bandgap inorganic materials have recently piqued the interest of the TPVD research community because they are nontoxic, low cost, and chemically stable. Substantial effort has been expended on exploring the use of these materials for TPVDs, with encouraging results. − In addition to optimizing photoactive materials, the charge collecting layer is a critical issue to completely utilize the function of TPVDs. Indium tin oxide (ITO) is commonly used as a transparent conducting layer for TPVDs; however, ITO is costly and can be a burden on the environment.…”

Promoting the Efficiency and Stability of Nonfullerene Organic Photovoltaics by Incorporating Open-Cage [60]Fullerenes in the Nonfullerene Nanocrystallites

“…We note that the degradation of the device efficiency is a compound issue and might result in changes in the active materials, interlayers, and electrodes. There are independent studies on the effects of the interlayers and the electrodes. , However, in our approach on the device stability, we have kept the interlayers and electrodes controlled and variated only the active layer. Accordingly, the consequences are mainly attributed to the active layer.…”

“…There are independent studies on the effects of the interlayers and the electrodes. 61,62 However, in our approach on the device stability, we have kept the interlayers and electrodes controlled and variated only the active layer. Accordingly, the consequences are mainly attributed to the active layer.…”