Researcher Zhu Rui, Academician Gong Qihuang and collaborators of the "Extreme Optics Innovation Research Team" at the School of Physics of Peking University conducted research for the first time using the "guanidine salt assisted secondary growth" technology to adjust the characteristics of perovskite semiconductors, improving Breakthroughs have been made in the performance of titanium ore solar cells, setting a record for the efficiency of such solar cell devices. The related research was published on June 29, 2018 in the international top academic journal "Science" (Enhanced photovoltage for inverted planar heterojunction perovskite solar cells, Science, Vol. 360, Issue 6396, pp. 1442-1446, DOI: 10.1126 / science.aap9282).

With the continuous progress of human society, the energy and environmental problems caused by industrial production have become increasingly prominent. The limited reserves of fossil fuels (oil, coal, natural gas, etc.) and the global warming caused by their combustion have prompted people to constantly look for And develop new and renewable energy sources. Solar energy has the advantages of clean, pollution-free, wide distribution and sufficient energy, and is one of the new energy sources that are promising for large-scale application. Solar cells use the photovoltaic effect to directly convert solar energy into electrical energy, which has received extensive attention and research from academia and industry, and has also received strong support from governments of various countries.

In recent years, perovskite solar cells have rapidly emerged as the new favorite in the field of new photovoltaic technology due to their advantages of simple preparation, low cost and high efficiency. Their photoelectric conversion efficiency has achieved a leaping growth in just eight years. The highest efficiency currently reported Has reached the efficiency level of commercialized monocrystalline silicon solar cells, showing great advantages and application potential.

Perovskite solar cells are divided into two device structures: nip and trans. Compared with formal devices, trans-structured devices have the advantages of simpler manufacturing processes, low-temperature film formation, no obvious hysteresis effect, and are suitable for the combination of traditional solar cells (silicon-based batteries, copper indium gallium selenium, etc.) to prepare stacked devices. , Has received more and more attention. However, there are some significant deficiencies in trans-structured devices. For example, the gap between the open circuit voltage and the theoretical value is large, and the photoelectric conversion efficiency is relatively low. This is mainly due to the existence of a large number of defects in the device. These defects mainly exist in the perovskite active layer, at the interface between the perovskite active layer and the charge collection layer, resulting in non-radiative recombination of photo-generated carriers, which in turn leads to serious energy loss, which ultimately limits the increase of open circuit voltage and photoelectric The improvement of conversion efficiency restricts the development of such structural devices.

In view of the bottleneck in the photoelectric conversion efficiency of trans-structured perovskite solar cells, researcher Zhu Rui, Academician Gong Qihuang and collaborators conducted a study, and for the first time proposed the "guanidine salt assisted secondary growth" method, which was a pioneering realization The control of the semiconductor characteristics of the perovskite thin film has significantly reduced the energy loss of non-radiative recombination in the device, and has made a breakthrough in improving the open circuit voltage of the device. Band gap width ~ 1.6 eV). At the same time, without loss of performance parameters such as photocurrent and fill factor, the photoelectric conversion efficiency of trans-structured perovskite batteries has been significantly improved-the highest efficiency of the laboratory reached 21.51%. Certified by the Chinese Academy of Metrology, the photoelectric conversion efficiency of the device is also as high as 20.90%, which is currently the highest record of the efficiency of trans-structured perovskite solar cell devices. This result provides new ideas for improving the efficiency of trans-perovskite solar cell devices and promoting the application of such new photovoltaic devices. This preparation technology is also expected to be further extended to perovskite stacked solar cells and perovskite light-emitting devices, with potential application prospects and commercial value.

Figure 1. Left: Trans-structure perovskite solar cell. Right: Photoluminescence of the battery device at a forward voltage (2 V) (indicating that the battery device has a lower non-radiative recombination energy loss).

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