Lead‐free perovskite‐inspired materials (PIMs) are gaining attention in optoelectronics due to their low toxicity and inherent air stability. Their wide bandgaps (≈2 eV) make them ideal for indoor light harvesting. However, the investigation of PIMs for indoor photovoltaics (IPVs) is still in its infancy. Herein, the IPV potential of a quaternary PIM, Cu2AgBiI6 (CABI), is demonstrated upon controlling the film crystallization dynamics via additive engineering. The addition of 1.5 vol% hydroiodic acid (HI) leads to films with improved surface coverage and large crystalline domains. The morphologically‐enhanced CABI+HI absorber leads to photovoltaic cells with a power conversion efficiency of 1.3% under 1 sun illumination—the highest efficiency ever reported for CABI cells and of 4.7% under indoor white light‐emitting diode lighting—that is, within the same range of commercial IPVs. This work highlights the great potential of CABI for IPVs and paves the way for future performance improvements through effective passivation strategies.

Colloidal lead-free perovskite nanocrystals have recently received extensive attention because of their facile synthesis, the outstanding size-tunable optoelectronic properties, and less or no toxicity in their commercial applications. Tin (Sn) has so far led to the most efficient lead-free solar cells, yet showing highly unstable characteristics in ambient conditions. Here, we propose the synthesis of all-inorganic mixture Sn-Ge perovskite nanocrystals, demonstrating the role of Ge 2+ in stabilizing Sn 2+ cation while enhancing the optical and photophysical properties. The partial replacement of Sn atoms by Ge atoms in the nanostructures effectively fills the high density of Sn vacancies, reducing the surface traps and leading to a longer excitonic lifetime and increased photoluminescence quantum yield. The resultant Sn-Ge nanocrystals-based devices show the highest efficiency of 4.9 %, enhanced by nearly 60 % compared to that of pure Sn nanocrystals-based devices.

Perovskites have lately attracted a lot of attention as promising materials for the next-generation of efficient, low-cost, and solution processable optoelectronics. Their complex transient photophysics, in time scales ranging from femtoseconds to seconds, have been widely investigated. However, in most of the reported works the spectral window of ultrafast transient absorption (TA) spectroscopy of perovskite films is limited to the visible region, hence missing crucial information coming from the near-infrared (NIR). Furthermore, the measured TA responses are affected by light interference in a thin perovskite layer making data interpretation a challenge even in the visible part of the spectrum. Here, we demonstrate a method that allows us to separately obtain the changes in absorption and refractive index from conventional transmission and reflection pump-probe measurements. We show that the contribution of the absorption change to the response of metal halide perovskite thin films in the NIR is much smaller than that of the refractive index change. Furthermore, the spectral shape of TA responses in the NIR range is predominantly determined by perovskite layer thickness and its refractive index. However, the time profile of the responses bears important information on the carrier dynamics and makes the NIR a useful range to study perovskite photophysics. † Electronic supplementary information (ESI) available: Method details for Dn and Dk calculations and transfer matrix based simulations, including a steady-state transmittance and reflectance simulation. ESI also has an example of primary TA absorption measurements and TA decay profiles and different excitation intensities. See

Antimony‐based perovskite‐inspired materials (PIMs) are solution‐processable halide absorbers with interesting optoelectronic properties, low toxicity, and good intrinsic stability. Their bandgaps around 2 eV make them particularly suited for indoor photovoltaics (IPVs). Yet, so far only the fully inorganic Cs3Sb2ClxI9−x composition has been employed as a light‐harvesting layer in IPVs. Herein, the first triple‐cation Sb‐based PIM (CsMAFA‐Sb) in which the A‐site of the A3Sb2X9 structure consists of inorganic cesium alloyed with organic methylammonium (MA) and formamidinium (FA) cations is introduced. Simultaneously, the X‐site is tuned to guarantee a 2D structure while keeping the bandgap nearly unchanged. The presence of three A‐site cations is essential to reduce the trap‐assisted recombination pathways and achieve high performance in both outdoor and indoor photovoltaics. The external quantum efficiency peak of 77% and the indoor power conversion efficiency of 6.4% are the highest values ever reported for pnictohalide‐based photovoltaics. Upon doping of the P3HT hole‐transport layer with F4‐TCNQ, the power conversion efficiency of CsMAFA‐Sb devices is fully retained compared to the initial value after nearly 150 days of storage in dry air. This work provides an effective compositional strategy to inspire new perspectives in the PIM design for IPVs with competitive performance and air stability.

Hot charge carriers (HC) are photoexcited electrons and holes that exist in nonequilibrium high-energy states of photoactive materials. Prolonged cooling time and rapid extraction are the current challenges for the development of future innovative HC-based optoelectronic devices, such as HC solar cells (HCSCs), hot energy transistors (HETs), HC photocatalytic reactors, and lasing devices. Based on a thorough analysis of the basic mechanisms of HC generation, thermalization, and cooling dynamics, this review outlines the various possible strategies to delay the HC cooling as well as to speed up their extraction. Various materials with slow cooling behavior, including perovskites and other semiconductors, are thoroughly presented. In addition, the opportunities for the generation of plasmon-induced HC through surface plasmon resonance and their technological applications in hybrid nanostructures are discussed in detail. By judiciously designing the plasmonic nanostructures, the light coupling into the photoactive layer and its optical absorption can be greatly enhanced as well as the successful conversion of incident photons to HC with tunable energies can also be realized. Finally, the future outlook of HC in optoelectronics is highlighted which will provide great insight to the research community.