Transparent luminescent solar concentrators (TLSCs) have been attracting wide attentions for their applications in transparent photovoltaic (PV) windows, smart greenhouses, and mobile electronics on account of the simple architecture and low-cost preparation. We report a novel strategy to fabricate TLSCs using the heterophase lead-free perovskites. The heterophase nanolayered films which combined CsCu 2 I 3 and Cs 3 Cu 2 I 5 were prepared in one step using a dual-source coevaporation technique. The CsCu 2 I 3 /Cs 3 Cu 2 I 5 films exhibited UV light absorption, a high average visible transmission (AVT) of 86.70%, and dual-color white emission between 350 and 760 nm. Importantly, the TLSCs incorporated with the CsCu 2 I 3 / Cs 3 Cu 2 I 5 films exhibited an impressive optical conversion efficiency of 1.15% under keeping a high AVT of 86.70%. Meanwhile, the TLSCs incorporated with the heterophase films showed considerable stability under ambient conditions. The CIE 1960 color coordinates (0.2082, 0.4680) of the TLSCs incorporated with the CsCu 2 I 3 /Cs 3 Cu 2 I 5 films showed excellent aesthetic quality as compared with those of the TLSCs incorporated with lead-based perovskites. Our finding offers a strategy to prepare lead-free metal halides toward high-performance TLSCs and future transparent PV windows.

Metal halides show a powerful potential to fabricate photothermoelectric (PTE) detectors due to their merits of ultra-low thermal conductivity, high Seebeck coefficient, and high carrier mobility. It is critically important to develop a flexible, transparent, and large-area PTE material for pushing its practical and extensive application. In this report, we fabricate a PTE-based detector employing lead-free Cs3Cu2I5 nanolayered film, which is prepared on a large area using a dual-source co-evaporation technique. Importantly, the PTE detector exhibits self-powered light response wavelengths ranging from visible (532 nm) to near-infrared (980 nm) to terahertz (119 μm). Moreover, we find that the photocurrent generation of the Cs3Cu2I5 photodetector by employing lateral device architecture is mainly originated from the PTE effect of Cs3Cu2I5 film. The PTE photodetector arrays incorporated with large-area Cs3Cu2I5 film also provide a successful application in flexible imaging. The results show that lead-free Cs3Cu2I5 is a promising PTE material for fabricating a flexible and self-powered ultra-broadband photodetector and provide insight into the utility of metal halides in thermal-induced ultra-broadband photodetection.

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As an alternative to the traditional blend casting method, a novel heterojunction doping approach is developed to dope hole extraction layers (HELs) for greatly boosting the efficiency of charge carrier collection in perovskite solar cells (PSCs). The HELs are prepared by sequential deposition of Cs-doped VO x and poly­(triarylamine) (PTAA) thin films, and extensive heterojunction doping is observed in the contact interface between the two thin films due to the presence of electron transfer from PTAA to Cs-doped VO x . The interfacial doping in the Cs-doped VO x /PTAA HELs enhances their conductivity and improves their energy level alignment. These increase V OC, J SC, FF, and power conversion efficiency (PCE) in PSCs compared to those in the PSCs with the use of Cs-doped VO x and PTAA separately.

Controlling the thermal conductivity of metal halide perovskites is of significance to promising applications ranging from optoelectronic devices to heat storage and conversion devices. Herein, we carry out the thermal management of bismuth halide perovskite. As measured by time-domain thermo-reflectance, the Cs3Bi2I9 thin film possesses a thermal conductivity of 0.15 W m–1 K–1 that is lower than that of the BiI3 thin film with a thermal conductivity of 0.31 W m–1 K–1. We attribute the differential thermal conductivity to the stronger phonon scattering of Cs3Bi2I9 at low frequencies as compared to that of BiI3. In addition, we fabricated photothermal detectors by employing BiI3 and Cs3Bi2I9 thin films with different heat transport characteristics. As a result, the detectors using Cs3Bi2I9 have a larger response temperature, stronger photocurrent, higher responsivity, and normalized detectivity than the detectors using BiI3. The unique heat transport characteristics provide a prospect for photothermal detection. Furthermore, the insights in this report imply opportunities to explore ultra-low thermal conductivity among metal halide perovskites.