Effects of the Morphology of a ZnO Buffer Layer on the Photovoltaic Performance of Inverted Polymer Solar Cells

Abstract

The influences of morphology and thickness of zinc oxide (ZnO) buffer layers on the performance of inverted polymer solar cells are investigated. ZnO buffer layers with different morphology and thickness varying from several nanometers to ≈55 nm are fabricated by adjusting the concentration of the precursor sol. The ZnO buffer layers with nearly same surface quality but with thickness varying from ≈7 to ≈65 nm are also fabricated by spinning coating for comparison. The photovoltaic performance is found to be strongly dependent on ZnO surface quality and less dependent on the thickness. The use of dense and homogenous ZnO buffer layers enhances the fill factor and short‐circuit current of inverted solar cell without sacrificing the open‐circuit voltage of device due to an improvement in the contact between the ZnO buffer layer and the photoactive layer. Inverted devices with a dense and homogenous ZnO buffer layer derived from 0.1 M sol exhibit an overall conversion efficiency of 3.3% which is a 32% increase compared to devices with a rough ZnO buffer layer made from 1 M sol, which exhibited a power conversion efficiency of 2.5%. The results indicate that the efficiency of inverted polymer solar cells can be significantly influenced by the morphology of the buffer layer.

Impact of sol aging on TiO2 compact layer and photovoltaic performance of perovskite solar cell

“…TiO2 dense film is used as the compact layer which plays an important role in charge transfer. It can effectively prevent charge recombination at the interface of fluorine-doped tin dioxide (FTO) and perovskite or hole transport material (HTM) layer [19][20][21]. Additionally, the compact layer can reduce energy barrier between FTO and the active layer, which benefits charge extraction.…”

“…The properties of TiO2 compact films vary with prepared methods, doping with other elements and surface treatments [21][22][23]. It has been demonstrated that the thickness, morphology and surface condition of the compact layer can affect the power conversion efficiency (PCE) of solar cells, whereas the compactness is a key character.…”

Enhanced Stability of Organic Photovoltaics by Additional ZnO Layers on Rippled ZnO Electron-collecting Layer using Atomic Layer Deposition

“…9,10 Various buffer layers (e.g., TiO 2 , and ZnO as electron-collecting layers and NiO, and MoO 3 as hole-collecting layers) were used in order to more efficiently separate electrons and holes created in active layers by absorption of light. [11][12][13][14][15] Nano-structuring of surfaces of buffer layers increased contact area between active polymer and buffer layers, increasing efficiency for electron-hole separation. 16,17 We have recently shown that ZnO ripple structures can be easily prepared using solution process combined with wellcontrolled heat treatment process.…”

Effect of Self-Assembled Monolayer Treated ZnO on the Photovoltaic Properties of Inverted Polymer Solar Cells

“…To address these challenges, the previous reports have revealed that the inverted PSC is as a promising alternative for obtaining high device performance, in which high work function metals (such as Ag and Au) are used as the anode while ITO is employed as the bottom cathode. [12][13][14] To develop high performance inverted PSCs, the nature of the electrical contacts between the organic semiconducting layer and the electrodes needs to be paid attention because it plays an essential role in determining device characteristics such as the open-circuit voltage (V oc ), the short-circuit current density (J sc ), the ll factor (FF), the series resistance (R s ), and the paralell (shunt) resistance (R p ), as well as the power conversion eciency (PCE). 15,16 In order to achieve a good contact (mechanical or electrical contact), various modifications of the electrodes have been investigated, including the introduction of appropriate charge collecting layers between the organic photoactive layer and the electrodes to increase the built-in potential and to decrease the contact resistance.…”