Enhancing Photoresponse and Photocurrent of Integrated Perovskite/Organic Solar Cells via Layer-by-Layer Processing

Perovskite solar cells have developed rapidly in recent years to almost rival silicon cells. To extend the photoresponse in the near-infrared region, integrated perovskite/organic solar cells (IPOSCs) have been developed. Typically, the organic bulk heterojunction (BHJ) in IPOSCs is built by one-step coating of a mixed solution of a donor and an acceptor. Here, we prepare the BHJ by layer-by-layer (LBL) processing. Compared to the traditional one-step coated IPOSCs (TOS device), the LBL-processed device (LBL device) exhibits a distinctly improved short-circuit current density (JSC) and power conversion efficiency. The TOS device shows a high photoresponse from about 400 to 900 nm, while the LBL device shows a high photoresponse extending to about 950 nm. Further research indicates that the extending photoresponse of the LBL-device is caused by the redshift of absorption of the organic BHJ. Meanwhile, the LBL-processed BHJ exhibits slightly improved carrier extraction and recombination. The introduction of LBL processing provides an approach to broaden the optical absorption range and photoresponse of IPOSCs.