Zhu Rui, a researcher at the 'Extreme Optical Innovation Research Team' of the School of Physics, Peking University, and the researcher and collaborators of Gong Qihuang conducted research for the first time using the 'salt-assisted secondary growth' technique to regulate the characteristics of perovskite semiconductors, and to enhance the trans-structured calcium. Breakthrough results in the performance of titanium ore solar cells have set a record for the efficiency of such solar cell devices. Related research was published on June 29, 2018 in the world's 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 advancement of human society, 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 burning have prompted people to constantly seek And the development of new renewable energy sources. Solar energy is clean, pollution-free, widely distributed and full of energy. It is one of the new energy sources that are promising for large-scale applications. Solar cells use the photovoltaic effect to directly convert sunlight into Electrical energy has received extensive attention and research from academia and industry, and has received strong support from governments.
In recent years, perovskite solar cells have rapidly emerged as the new darling of new photovoltaic technology with their advantages of simple preparation, low cost and high efficiency. Their photoelectric conversion efficiency has jumped in just eight years, and the highest efficiency reported so far. The efficiency level of commercial monocrystalline silicon solar cells has been reached, showing great advantages and application potential.
Perovskite solar cells are divided into formal (nip) and trans (pin) device structures. Compared with formal devices, trans-structure devices are simpler to prepare, can form films at low temperatures, and have no significant hysteresis effect. The advantages of combining a conventional solar cell (silicon-based battery, copper indium gallium selenide, etc.) to prepare a stacked device have attracted more and more attention. However, trans structural devices also have some significant disadvantages, for example, open circuit voltage and theoretical value. The gap is large, and the photoelectric conversion efficiency is relatively low, which is mainly caused by a large number of defects in the device. These defects are mainly present in the active layer of the perovskite, at the interface between the active layer of perovskite and the charge collection layer, resulting in The non-radiative recombination of photogenerated carriers leads to serious energy loss, which ultimately limits the improvement of open circuit voltage and the improvement of photoelectric conversion efficiency, which restricts the development of such structural devices.
In view of the bottleneck in the photoelectric conversion efficiency of trans-structured perovskite solar cells, Zhu Rui, a researcher and collaborator of Gong Qihuang, conducted a research and proposed the method of 'salt-assisted auxiliary secondary growth' for the first time. The regulation of the characteristics of the perovskite thin film semiconductor significantly reduces the energy loss of the non-radiative recombination in the device, and has made a breakthrough in improving the open circuit voltage of the device. For the first time, a high open circuit voltage of more than 1.21 V was obtained in the trans-structure device (material) The band gap width is ~1.6 eV). At the same time, the photoelectric conversion efficiency of the trans-structured perovskite battery is significantly improved without losing the performance parameters such as photocurrent and fill factor - the highest efficiency in the laboratory is 21.51%. According to the China Institute of Metrology, the photoelectric conversion efficiency of the device is as high as 20.90%, which is the highest record of the efficiency of the trans-structured perovskite solar cell device. The result is to improve the efficiency of the trans-perovskite solar cell device. The application of new types of photovoltaic devices provides new ideas. This preparation technology is also expected to further expand to perovskite stratified solar energy. Pool and perovskite light emitting device, has potential applications and business value.
Figure 1. Left: Trans-structured perovskite solar cells. Right: Photograph of the luminescence of the battery device at forward voltage (2 V) (indicating that the battery device has a low non-radiative composite energy loss).
