Abstract
The efficiency of perovskite solar cells has surged in the past few years, while the bandgaps of current perovskite materials for record efficiencies are much larger than the optimal value, which makes the efficiency far lower than the Shockley–Queisser efficiency limit. Here we show that utilizing the below-bandgap absorption of perovskite single crystals can narrow down their effective optical bandgap without changing the composition. Thin methylammonium lead triiodide single crystals with tuned thickness of tens of micrometers are directly grown on hole-transport-layer covered substrates by a hydrophobic interface confined lateral crystal growth method. The spectral response of the methylammonium lead triiodide single crystal solar cells is extended to 820 nm, 20 nm broader than the corresponding polycrystalline thin-film solar cells. The open-circuit voltage and fill factor are not sacrificed, resulting in an efficiency of 17.8% for single crystal perovskite solar cells.
Highlights
The efficiency of perovskite solar cells has surged in the past few years, while the bandgaps of current perovskite materials for record efficiencies are much larger than the optimal value, which makes the efficiency far lower than the Shockley–Queisser efficiency limit
We report the growth of perovskite single crystals directly onto hole transport layer (HTL) covered indium tin oxide (ITO) substrates with controlled thickness of tens of micrometer and area of tens of millimeter square
Solar cells based on the thin single crystals show obviously broader spectral response compared to the polycrystalline thin-film solar cells, while the open-circuit voltage (VOC) and fill factor (FF) of the solar cells remain comparable to those of polycrystalline thin-film solar cells, which demonstrates the potential for the application of perovskite single crystals to further boost the efficiency of perovskite solar cells
Summary
The efficiency of perovskite solar cells has surged in the past few years, while the bandgaps of current perovskite materials for record efficiencies are much larger than the optimal value, which makes the efficiency far lower than the Shockley–Queisser efficiency limit. The efficiency of OIHP solar cells has reached 22.1% quickly after development in a few years by the improvement of material quality and device interface[9], but it is facing a bottleneck caused by the non-optimized bandgap of the current perovskite materials. Similar to silicon single crystal solar cells, further improvement of the device efficiency may be achieved by utilizing the below-bandgap absorption. Current studies of the intrinsic properties of the perovskites are mainly based on thick bulk single crystals with thickness of millimeter[27,28] which are too thick for application in solar cells. We report the growth of perovskite single crystals directly onto hole transport layer (HTL) covered indium tin oxide (ITO) substrates with controlled thickness of tens of micrometer and area of tens of millimeter square (mm[2]). Solar cells based on the thin single crystals show obviously broader spectral response compared to the polycrystalline thin-film solar cells, while the open-circuit voltage (VOC) and fill factor (FF) of the solar cells remain comparable to those of polycrystalline thin-film solar cells, which demonstrates the potential for the application of perovskite single crystals to further boost the efficiency of perovskite solar cells
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