Won Hyun Shim

Influence of surface roughness of aluminum-doped zinc oxide buffer layers on the performance of inverted organic solar cells

Aluminum-doped zinc oxide (AZO) films (70 nm thick) with dissimilar surface roughness were created on indium tin oxide coated glass and were used as electrodes for inverted organic solar cells. The photovoltaic performance of the devices depended strongly on the surface roughness of the AZO films. Increases in the surface root-mean-square roughness of AZO films from 2.5 to 10.9 nm enhanced power conversion efficiency from 0.5% to 1.4% due to increased contact area between electrode and active layer.

Multifunctional SWCNT‐ZnO Nanocomposites for Enhancing Performance and Stability of Organic Solar Cells

Photovoltaic systems have been extensively studied and, among them, organic solar cells (OSCs) have attracted particular attention due to their low price and the possibility of using them in fl exible devices. [ 1–4 ] One of the disadvantages of OSCs is their low chemical stability, which is due to the oxidation of their interfaces by oxygen and water and the photodegradation of the active layers. [ 5–9 ] In order to increase their stability, various methods have been employed. Oxygen and water diffusion barriers were employed to protect the interfaces of OSCs from degradation. [ 10 , 11 ] Recently, an OSC with an inverted structure was developed, which was shown to be more stable than conventional solar cells. [ 12 , 13 ] In conventional structures, holes are injected into the transparent conducting electrode (TCE) and, in many cases, materials such as PEDOT: PSS with a high capability of hole injection are deposited on the TCE. In the inverted structure, in contrast, electrons are injected into the TCE. In the past, the improved stability of the inverted structure based on n-type ZnO layers on a TCE with respect to that of conventional OSCs was reported. [ 12 , 13 ] Carbon nanotubes (CNTs) have been widely used in photovoltaic systems. In many cases, bare CNTs and CNTs combined with C 60 , semiconductive and metallic nanoparticles were incorporated in the active layers, and the high capability of CNTs for electron transport has been exploited. [ 14–20 ] On the other hand,

Effect of Sol-Gel Prepared ZnO Electron Selective Layer on the Performance of Inverted Organic Solar Cells

ZnO buffer layer was prepared as electron selective layers (ESL) for photo-induced electron transport and hole blocking in inverted organic solar cells (IOSCs) by sol-gel process. The effects of thickness and surface roughness of ZnO ESL on the performance of IOSCs were investigated. Power Conversion Efficiency (PCE) of the IOSC strongly varied as a function of ZnO film thickness and surface roughness, in particular, when the film thickness was <70 nm, increase in the surface roughness enhanced photovoltaic performances. It is demonstrated that optimization of the electrode thickness and roughness is essential for obtaining better performance of organic photovoltaic cells.