A bi-functional structure with tunable electrical and optical properties for organic photovoltaic cells

Abstract

We have successfully developed a C60:LiF/BCP (bathocuproine) bilayer-buffer structure to optimize both the light absorption enhancement and the exciton-blocking at the cathode interface of a small molecular photovoltaic cell based on the archetypical CuPc/C60 structure. The function of the C60:LiF layer is to serve as an optical spacer and is found to yield a peak power conversion efficiency (PCE) with a 50 wt. % LiF at a thickness of 30 nm. A BCP layer is added between the optimized C60:LiF layer and the Al metal electrode to function as a barrier for excitons. This combined bilayer-buffer structure yields an optimal performance in short circuit current (Jsc) and PCE. A detailed study using a single carrier electron-only structure and a numerical simulation of optical electric-field distribution suggests that C60:LiF layer enhances light absorption at long wavelengths.

Favorable electronic structure for organic solar cells induced by strong interaction at interface

“…4 However, other interpretations were also proposed to explain the role of BCP, such as increasing the built-in field, acting as an optical spacer, reducing nonradiative recombination of excitons at the fullerene (C 60 )/Al interface, avoiding the formation of aluminum carbide, and so on. 12,13 Anyway, the working mechanism is still controversial.…”

“…However, we found the electronic properties of BCP/metal interface are strongly dependent on the metal's WF by forming different dipole layers. 13 Moreover, it has been demonstrated that the energy level alignment of C 60 /BCP/Ag interfaces can be drastically influenced by BCP layer thickness. 12 This suggests that the increase of electric built-in field is not the only reason for the efficiency enhancement for OSC with BCP and low WF cathode, and other reasons should be considered.…”

Light-modulating pressure sensor with integrated flexible organic light-emitting diode

“…The cost of manufacturing optoelectronic devices is thus reduced rapidly [6,22], particularly when integrable light detection systems are taken into account [1,23], making them a viable alternative technology advantages over more classical designs such as silicon-based pressure sensors. Optoelectronic sensors have other advantages [24], such as negating the need for vacuum cavities to maintain high Q-factors needed for resonant devices [25,26].…”

“…Their most significant drawbacksshort lifetime and efficiency [1][2][3][4]-have been improved dramatically due to the intense research activity in this area in recent years. Being an innate surface-emitting light source, OLEDs are showing great commercial potential in the lighting industry, in mobile devices, and even in OLED televisions.…”

P‐164: Energy Transfer from Interface Exciplexes to Ultrathin Emissive Layers: A Path Way to Design Simplified Efficient White Tandem Organic Light‐Emitting Diodes for Application

“…The designed monochromatic tandem OLEDs show lower working voltage and better efficiency than those of the single-luminescent-unit OLED without exciplex-forming architecture. [4][5][6][7] Herein, we go a significant step further to fabricate a novel highly simplified efficient tandem WOLED structure using energy transfer from exciplexes to complementary color doping-free UEMLs ((acetylacetonato)bis[2-(thieno[3,2-c]pyridin-4yl)phenyl]iridium(III) (PO-01) as yellow emitter and iridium(III) bis[(4,6-difluorophenyl)-pyridinato-N,C2′]-picolinate (FIrpic) as blue emitter). Particularly, the designed current-driven WOLEDs obtaining a peak of 40.53 cd/A (EQE=18.15%).…”