Abstract
Solution-processed zinc oxide (ZnO)-based planar heterojunction perovskite photovoltaic device is reported in this study. The photovoltaic device benefits from the ZnO film as a high-conductivity and high-transparent electron transport layer. The optimal electron transport layer thickness and post-baking temperature for ZnO are systematically studied by scanning electron microscopy, photoluminescence and time-resolved photoluminescence spectroscopy, and X-ray diffraction. Optimized perovskite solar cells (PSCs) show an open-circuit voltage, a short-circuit current density, and a fill factor of 1.04 V, 18.71 mA/cm2, and 70.2%, respectively. The highest power conversion efficiency of 13.66% was obtained when the device was prepared with a ZnO electron transport layer with a thickness of ~20 nm and when post-baking at 180 °C for 30 min. Finally, the stability of the highest performance ZnO-based PSCs without encapsulation was investigated in detail.
Highlights
Organometal-trihalide perovskite-structured photovoltaic devices (CH3NH3PbX3, X = Cl, Br or I) have received much attention because of their outstanding power conversion efficiency (PCE) and unique optoelectronic characteristics
The surface of zinc oxide (ZnO) has been modified by thermal annealing to remove the hydroxide [29], and a buffer layer, such as phenyl-C61-butyric acid methyl ester (PCBM) and poly(ethylenimine) (PEI), has been placed between the perovskite and ZnO layers to minimize the effect of the surface state of ZnO on the performance of the perovskite solar cells (PSCs) [28]
The stability of the performance of the perovskite photovoltaic device was determined over the course of more than 1300 h
Summary
The ZnO electron transport layer can be deposited through electrodeposition [17], atomic layer deposition [18,19,20], or spin-coating [21,22,23] These methods are carried out without the need for a high-temperature sintering step, so it is an ideal material for deposition onto thermally sensitive substrates, such as ITO glass or ITO/PET substrates. The problem is that low-temperature processing leaves surface hydroxyl groups and/or residual acetate ligands on the surface of ZnO, and the hydroxyl group decomposes CH3 NH3 PbI3 into PbI2 and CH3 NH3 I [28,29] To avoid this process, the surface of ZnO has been modified by thermal annealing to remove the hydroxide [29], and a buffer layer, such as PCBM and poly(ethylenimine) (PEI), has been placed between the perovskite and ZnO layers to minimize the effect of the surface state of ZnO on the performance of the PSCs [28]. The stability of the performance of the perovskite photovoltaic device was determined over the course of more than 1300 h
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