Extending the Absorption Spectra and Enhancing the Charge Extraction by the Organic Bulk Heterojunction for CsPbBr<sub>3</sub> Perovskite Solar Cells
Beilei Yuan, Yu Zhou, Ting Liu, Cuncheng Li, Bingqiang Cao
Abstract
Among the various lead halide perovskites, inorganic cesium lead bromide (CsPbBr 3 ) was considered as a promising candidate for new solar cells because of its unique photophysical properties and outstanding stabilities in a high-humidity, high-temperature, or ambient atmosphere. However, the efficiency is still quite limited due to the inefficient charge transfer and narrow spectra. In this work, we report that integrating the P3HT/PCBM bulk heterojunction (BHJ) organic layer with the CsPbBr 3 films can sharply enhance the spectral absorption from 540 to 680 nm and simultaneously enhance the charge extraction ability at the CsPbBr 3 /carbon interface. At the same time, the carbonyl group and thiophene units in the BHJ group can inhibit the production of Pb 0 defects and passivate the under-coordinated Pb 2+, thus reducing trap density, retarding charge recombination, and improving charge transport and extraction. Using this strategy, the efficiency of BHJ/CsPbBr 3 solar cells is improved from 5.36 to 8.15%. In addition, the integrated devices have superior long-term stability, and unpackaged devices can maintain an initial efficiency of 90% within 40 days. This work provides an avenue for the industrial application of this integrated device in the future.