Work Function Of MoO3 Research Articles

Synthesis, characterization and photovoltaic properties of three new 3,4-dithienyl-substituted polythiophene derivatives

Three 3,4-dithienyl-substituted polythiophene derivatives have been synthesized and characterized. Polymer P2 exhibits the widest light absorption spectrum of the polymers in its polymer chain, which has an alternative donor-acceptor structure. Copolymers blended with 6,6-phenyl-C71-butyric acid methyl ester(PC71BM) as active layers are used to fabricate polymer solar cells (PSCs), and a variety of post-treatments are employed to optimize the PSCs performance. A maximum power conversion efficiency (PCE) of 1.22% is achieved for the conventional configuration device based on P2, and the inverted configuration device of P2 is also prepared for comparison. The results show that the inverted P2 device exhibits a better PCE (1.47%) than that of the conventional device due to the TiO2 nanoparticles and the close energy alignment between the work function of the MoO3 and the HOMO energy levels, which facilitate a light absorption increase and improved charge transport. Three new copolymers P1, P2, P3 have been synthesized and characterized. A variety of post-treatments are employed to optimize the performance of solar cells based on these copolymers. A maximum power conversion efficiency (PCE) of 1.22% is achieved by P2 in conventional configuration cells. The PCE of P2 can be further enhanced with inverted configuration, which is ascribe to the more light absorption by TiO2 nanoparticles and the close energy alignment between the work function of MoO3 and the HOMO energy levels of P2.

Synthesis and Photovoltaic Properties of New Multifused Anthradithiophene‐Based Narrow‐Bandgap D–A Copolymers

Three structurally novel donor–acceptor copolymers are synthesized and fully characterized using an anthradithiophene (ADT) derivative as the donor block. All of them exhibit broad absorption ranges and moderate hole and electron mobilities. The multifused ADT donor block makes them exhibit lower highest occupied molecular orbital (HOMO) energy levels than many reported benzodithiophene‐based polymers. Copolymer blends with [6,6]‐phenyl C71 butyric acid methyl ester (PC71BM) as active layers are used to fabricate polymer solar cells (PSCs) and a variety of post‐treatment methods are employed to optimize the device performance. The conventional and inverted configuration devices are prepared to evaluate the photovoltaic properties. A maximum power conversion efficiency of 1.66% is achieved for the inverted‐configuration device. The improved efficiency is caused by the close energy alignment between the work function of MoO3 and the HOMO energy levels of the copolymers, facilitating better charge transport and increased short‐circuit current density (Jsc) with the inverted devices. image

Enhanced Extraction Rates through Gap States of Molybdenum Oxide Anode Buffer

Molybdenum oxide (MoO3) is a promising anode buffer layer (ABL) for high-performance organic photovoltaic (OPV) devices. However, the reasons for the enhanced performances remain unclear. In this work, we show that defect states play an important, if not dominating, role in improving the OPV performances. The changes in both the density of defect states and the work function of MoO3 with annealing are shown and correlated with the OPV device performance. The increased defect densities improve the OPV performance through an enhanced hole extraction rate at the MoO3/organic interface. The reduction in work function, however, reduces the interface field that can possibly lower mobility near the interface and reduce the electron-blocking effect. This plays a role in saturation of the device performance. This work, therefore, shows the importance of the defects in MoO3 as an ABL and a dominance of defect-enhanced extraction over a field-enhanced extraction process.