Abstract
The hole blocking layer plays an important role in suppressing recombination of holes and electrons between the perovskite layer and fluorine-doped tin oxide (FTO). Morphological defects, such as cracks, at the compact TiO2 hole blocking layer due to rough FTO surface seriously affect performance of perovskite solar cells (PSCs). Herein, we employ a simple spin-coating SnO2 thin film solution to cover cracks of TiO2 hole blocking layer for PSCs. The experiment results indicate that the TiO2/SnO2 complementary composite hole blocking layer could eliminate the serious electrical current leakage existing inside the device, extremely reducing interface defects and hysteresis. Furthermore, a high efficiency of 13.52% was achieved for the device, which is the highest efficiency ever recorded in PSCs with spongy carbon film deposited on a separated FTO-substrate as composite counter electrode under one sun illumination.
Highlights
Perovskite solar cells (PSCs) have been recognized as the most promising alternatives to conventional silicon solar cells due to high conversion efficiency, low manufacturing cost, and simple process [1,2,3,4,5,6,7]
scanning electron microscope (SEM) surface image of the red square, the bottom fluorine-doped tin oxide (FTO) can be seen through the cracks, which will cause a large number of photocarriers to be recombination and seriously affect the performance of the perovskite solar cells (PSCs) device
The cross-sectional SEM image of bare FTO layer is shown in Figure 1e, we can find that the surface of bare FTO layer was very rough due to the presence of sharp peaks
Summary
Perovskite solar cells (PSCs) have been recognized as the most promising alternatives to conventional silicon solar cells due to high conversion efficiency, low manufacturing cost, and simple process [1,2,3,4,5,6,7]. As for typical planar heterojunction PSCs composed of working electrode (cathode)/hole blocking layer/perovskite layer/electron blocking layer/counter electrode (anode), the hole blocking layer plays an important role in extracting electrons from the perovskite layer and, as well as, suppressing recombination of holes and electrons between the perovskite layer and FTO [8,9,10,11]. A uniform, pinhole-free and well electrically conductive hole blocking layer is highly demanded for well performed planar heterojunction PSCs [8,12]. Liao et al found that the pinholes on the surface of the single SnO2 hole blocking layer coating on the rough FTO substrate were still hard to eliminate. TiO2 /SnO2 bilayer as hole blocking layer to improve device performance [8,13]. TiO2 compact layer has commonly been used as the hole blocking layer in the planar heterojunction
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