Hybrid organic-inorganic perovskite solar cells have recently emerged as a highly promising and inexpensive solution for sustainable energy. However, a full comprehensive picture of the phase transition including structural evolution and crystal growth mechanisms is missing for both scalable printing and lab-based spin-coating processes. Here we reveal fundamental insights into the perovskite phase transition when moving between spin-coating and printing processes, providing a rational path toward optimization of printed devices.

We report a Ruddlesden–Popper/3D heterostructure combined with molecule passivation within α-phase FAPbI3 films for high-performance and ambient-air-stable solar cells.

Perovskite solar cells based on two-dimensional/three-dimensional (2D/3D) hierarchical structure have attracted significant attention in recent years due to their promising photovoltaic performance and stability. However, obtaining a detailed understanding of interfacial mechanism at the 2D/3D heterojunction, for example, the ligand-chemistrydependent nature of the 2D/3D heterojunction and its influence on charge collection and the final photovoltaic outcome, is not yet fully developed. Here we demonstrate the underlying 3D phase templates growth of quantum wells (QWs) within a 2D capping layer, which is further influenced by the fluorination of spacers and compositional engineering in terms of thickness distribution and orientation. Better QW alignment and faster dynamics of charge transfer at the 2D/3D heterojunction result in higher charge mobility and lower charge recombination loss, largely explaining the significant improvements in charge collection and open-circuit voltage (V OC ) in complete solar cells. As a result, 2D/3D solar cells with a power-conversion efficiency of 21.15% were achieved, significantly higher than the 3D counterpart (19.02%). This work provides key missing information on how interfacial engineering influences the desirable electronic properties of the 2D/3D hierarchical films and device performance via ligand chemistry and compositional engineering in the QW layer.

All‐inorganic CsPbI3 holds promise for efficient tandem solar cells, but reported fabrication techniques are not transferrable to scalable manufacturing methods. Herein, printable CsPbI3 solar cells are reported, in which the charge transporting layers and photoactive layer are deposited by fast blade‐coating at a low temperature (≤100 °C) in ambient conditions. High‐quality CsPbI3 films are grown via introducing a low concentration of the multifunctional molecular additive Zn(C6F5)2, which reconciles the conflict between air‐flow‐assisted fast drying and low‐quality film including energy misalignment and trap formation. Material analysis reveals a preferential accumulation of the additive close to the perovskite/SnO2 interface and strong chemisorption on the perovskite surface, which leads to the formation of energy gradients and suppressed trap formation within the perovskite film, as well as a 150 meV improvement of the energetic alignment at the perovskite/SnO2 interface. The combined benefits translate into significant enhancement of the power conversion efficiency to 19% for printable solar cells. The devices without encapsulation degrade only by ≈2% after 700 h in air conditions.

All-inorganic halide perovskites hold promise for emerging thin-film photovoltaics due to their excellent thermal stability. Unfortunately, it has been challenging to achieve high-quality thin films over large areas using scalable methods under realistic ambient conditions. Here, we provide important lessons on controlling the solidification and crystallization of CsPbI2Br perovskite inks during ambient scalable fabrication, with results of superior thin-film quality and device performance compared to lab-scale processes.

Two-dimensional (2D) Ruddlesden–Popper (RP) organic–inorganic perovskites have emerged as promising candidates for solar cells with technologically relevant stability. Herein, a new RP perovskite, the fifth member (⟨n⟩ = 5) of the (CH3(CH2)2NH3)2(CH3NH3) n−1Pb n I3n+1 family (abbreviated as PA2MA4Pb5I16), was synthesized and systematically investigated in terms of photovoltaic application. The obtained pure PA2MA4Pb5I16 crystal exhibits a direct band gap of E g = 1.85 eV. Systematic analysis on the solid film highlights the key role of the precursor–solvent interaction in the quantum well orientation, phase purity, grain size, surface quality, and optoelectronic properties, which can be well-tuned with addition of dimethyl sulfoxide (DMSO) into the N,N-dimethylformamide (DMF) precursor solution. These findings present opportunities for designing a high-quality RP film with well-controlled quantum well orientation, micrometer-sized grains, and optoelectronic properties. As a result, we achieved power conversion efficiency (PCE) up to 10.41%.

X-ray detectors are extensively utilized, including in medical diagnosis, scientific research, and security screening. So far, X-ray detectors have been developed mainly on the basis of metal-based semiconductors. Recently, in addition to traditional Si, Cd(Zn)Te and Ge, crystals based on metal halide perovskites have emerged as a new generation of semiconductors for radiation detection due to their high-Z elements Pb, Bi, and Br. [1-3] However, the requirements for practical wearable materials to be lightweight, economically inexpensive, and environmentally friendly motivate the exploration for nontoxic, low-cost, and simple organic compounds. [4] Lightweight semiconductors based on conjugated molecules or polymers have been demonstrated in a proof-of-principle manner for direct X-ray detection, including 4-hydroxycyanobenzene (4HCB), 1,8-naphthaleneimide (NTI), 1,5-dinitronaphthalene, and rubrene. [5-7] However, the fabrication of large-scale crystals with exceptionally Metal-free halide perovskites, as a specific category of the perovskite family, have recently emerged as novel semiconductors for organic ferroelectrics and promise the wide chemical diversity of the ABX 3 perovskite structure with mechanical flexibility, light weight, and eco-friendly processing. However, after the initial discovery 17 years ago, there has been no experimental information about their charge transport properties and only one brief mention of their optoelectronic properties. Here, growth of large single crystals of metalfree halide perovskite DABCO-NH 4 Br 3 (DABCO = N-N′-diazabicyclo[2.2.2] octonium) is reported together with characterization of their instrinsic optical and electronic properties and demonstration, of metal-free halide perovskite optoelectronics. The results reveal that the crystals have an unusually large semigap of ≈16 eV and a specific band nature with the valence band maximum and the conduction band minimum mainly dominated by the halide and DABCO 2+ , respectively. The unusually large semigap rationalizes extremely long lifetimes approaching the millisecond regime, leading to very high charge diffusion lengths (tens of µm). The crystals also exhibit high X-ray attenuation as well as being lightweight. All these properties translate to high-performance X-ray imaging with sensitivity up to 173 µC Gy air −1 cm −2. This makes metal-free perovskites novel candidates for the next generation of optoelectronics.

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