A novel approach for designing efficient broadband photodetectors expanding from deep ultraviolet to near infrared

Broadband photodetection (PD) covering the deep ultraviolet to near-infrared (200-1000 nm) range is significant and desirable for various optoelectronic designs. Herein, we employ ultraviolet (UV) luminescent concentrators (LC), iodine-based perovskite quantum dots (PQDs), and organic bulk heterojunction (BHJ) as the UV, visible, and near-infrared (NIR) photosensitive layers, respectively, to construct a broadband heterojunction PD. Firstly, experimental and theoretical results reveal that optoelectronic properties and stability of CsPbI3 PQDs are significantly improved through Er3+ doping, owing to the reduced defect density, improved charge mobility, increased formation energy, tolerance factor, etc. The narrow bandgap of CsPbI3:Er3+ PQDs serves as a visible photosensitive layer of PD. Secondly, considering the matchable energy bandgap, the BHJ (BTP-4Cl: PBDB-TF) is selected as to NIR absorption layer to fabricate the hybrid structure with CsPbI3:Er3+ PQDs. Thirdly, UV LC converts the UV light (200-400 nm) to visible light (400-700 nm), which is further absorbed by CsPbI3:Er3+ PQDs. In contrast with other perovskites PDs and commercial Si PDs, our PD presents a relatively wide response range and high detectivity especially in UV and NIR regions (two orders of magnitude increase that of commercial Si PDs). Furthermore, the PD also demonstrates significantly enhanced air- and UV- stability, and the photocurrent of the device maintains 81.5% of the original one after 5000 cycles. This work highlights a new attempt for designing broadband PDs, which has application potential in optoelectronic devices.