Toward Broad Spectral Response Inverted Perovskite Solar Cells: Insulating Quantum‐Cutting Perovskite Nanophosphors and Multifunctional Ternary Organic Bulk‐Heterojunction

Abstract Extending near‐infrared (NIR) spectral response and increasing ultraviolet utilization is still a challenge in the context of improving power conversion efficiency (PCE) for perovskite solar cells (PSCs). In this work, to extend NIR light‐harvesting of PSCs, a novel COTIC‐4F: PC₆₁BM: PTB7‐Th ternary organic bulk‐heterojunction together with Au nanotriangles is integrated on the PSCs. The NIR spectral response is thus extended to 1100 nm. In fact, the COTIC‐4F: PC₆₁BM: PTB7‐Th layer enables multi‐functional effects, which can serve as electron transport, trap passivation, and moisture barrier layer in addition to NIR light harvesting. For increasing UV utilization, CsPbCl₃:Yb³⁺, Ce³⁺, Cr³⁺ nanophosphors with photoluminescent quantum yield close to 200% are fabricated, which demonstrate excellent down‐conversion ability. Then, CsPbCl₃: Yb³⁺, Ce³⁺, Cr³⁺/polymethylmethacrylate composite films are self‐assembled on a hybrid device, resulting in a 6.2% relative enhancement of short circuit current density. After simultaneously improving the NIR and UV spectral response of device, the PCE is increased significantly from 20.52% to 23.40% and the Jsc is increased from 21.79 to 25.96 mA cm⁻², representing one of the highest PCE and maximum Jsc enhancements in the reported inverted hybrid organic/PSCs. This work represents an effective and general strategy for obtaining efficient and stable PSC devices with extremely broad spectral responses.