We report a careful and systematic study of thermal and photochemical degradation of a series of complex haloplumbates APbX (X = I, Br) with hybrid organic (A = CHNH) and inorganic (A = Cs) cations under anoxic conditions (i.e., without exposure to oxygen and moisture by testing in an inert glovebox environment). We show that the most common hybrid materials (e.g., MAPbI) are intrinsically unstable with respect to the heat- and light-induced stress and, therefore, can hardly sustain the real solar cell operation conditions. On the contrary, the cesium-based all-inorganic complex lead halides revealed far superior stability and, therefore, provide an impetus for creation of highly efficient and stable perovskite solar cells that can potentially achieve pragmatic operational benchmarks.

We report here all inorganic CsPbI planar junction perovskite solar cells fabricated by thermal coevaporation of CsI and PbI precursors. The best devices delivered power conversion efficiency (PCE) of 9.3 to 10.5%, thus coming close to the reference MAPbI-based devices (PCE ≈ 12%). These results emphasize that all inorganic lead halide perovskites can successfully compete in terms of photovoltaic performance with the most widely used hybrid materials such as MAPbI.

In the present Communication we discuss a field-induced and photoinduced self-doping chemistry resulting in the formation of the positively and negatively charged vacancies in the MAPbI3 perovskite films. These vacancies induce p-type and n-type doping of the perovskite absorber leading to the realization of the p-i-n device operation mechanism.

This paper presents a systematic study of the influence of electron‐transport materials on the operation stability of the inverted perovskite solar cells under both laboratory indoor and the natural outdoor conditions in the Negev desert. It is shown that all devices incorporating a Phenyl C61 Butyric Acid Methyl ester ([60]PCBM) layer undergo rapid degradation under illumination without exposure to oxygen and moisture. Time‐of‐flight secondary ion mass spectrometry depth profiling reveals that volatile products from the decomposition of methylammonium lead iodide (MAPbI3) films diffuse through the [60]PCBM layer, go all the way toward the top metal electrode, and induce its severe corrosion with the formation of an interfacial AgI layer. On the contrary, alternative electron‐transport material based on the perylendiimide derivative provides good isolation for the MAPbI3 films preventing their decomposition and resulting in significantly improved device operation stability. The obtained results strongly suggest that the current approach to design inverted perovskite solar cells should evolve with respect to the replacement of the commonly used fullerene‐based electron‐transport layers with other types of materials (e.g., functionalized perylene diimides). It is believed that these findings pave a way toward substantial improvements in the stability of the perovskite solar cells, which are essential for successful commercialization of this photovoltaic technology.

We report the first systematic assessment of intrinsic photothermal stability of a large panel of complex lead halides APbX3 incorporating different univalent cations (A = CH3NH3 +, [NH2CHNH2]+, Cs+) and halogen anions (X = Br, I) using a series of analytical techniques such as UV–vis and X-ray photoelectron spectroscopy, X-ray diffraction, EDX analysis, atomic force and scanning electron microscopy, ESR spectroscopy, and mass spectrometry. We show that heat stress and light soaking induce a severe degradation of perovskite films even in the absence of oxygen and moisture. The stability of complex lead halides increases in the order MAPbBr3 < MAPbI3 < FAPbI3 < FAPbBr3 < CsPbI3 < CsPbBr3, thus featuring all-inorganic perovskites as the most promising absorbers for stable perovskite solar cells. An important correlation was found between the stability of the complex lead halides and the volatility of univalent cation halides incorporated in their structure. The established relationship provides useful guidelines for designing new complex metal halides with immensely improved stability.

important problem is related to the high acute and chronic toxicity of the lead compounds, which can cause occupational health risks and hinder massive industrial production of raw materials and photovoltaic modules. [3] The need for recycling of the lead-containing photovoltaic panels at the end of their life cycle represents another issue, which has been experienced already in the case of CdTe technology. [4] Thus, the facile photo degradation of complex iodoplumbates and their anticipated negative impact on the environment provide impetus for the development of alternative lead-free light absorbers based on metal halides. [5] Complex tin (II) and germanium (II) halides with the perovskite crystal lattice were thoroughly investigated in effort to develop a new generation of light harvesting materials for solar cells. However, ASnX 3 and AGeX 3 systems (A represents organic cation and X = I, Br) delivered inferior photovoltaic efficiencies, while demonstrating even lower intrinsic stability than the iodoplumbates due to easy disproportionation of M (II) into M (0) and M (IV). [6] Therefore, the most recent efforts have been focused on the exploration of halide complexes of the posttransition group 15 elements such as Bi and Sb. Along with the pioneering reports on BiI 3[7] and A 3 Bi 2 I 9 (A = MA or Cs), [8] a number of other bismuth halides were considered such as BiSI, BiOI, AgBi 2 I 7 , and Cs 2 AgBiX 6 (X = Br, Cl). [9] The range of antimony (III) halides investigated in photovoltaic cells is limited to A 3 Sb 2 I 9 (A = MA, Rb, Cs). [10] Unfortunately, all binary and complex Bi(III) and Sb(III) halides so far tested delivered rather modest photovoltaic performances ranging from 0.1% to 1.2%. Low external quantum efficiencies (EQEs <20-30%) strongly suggest inefficient generation of charge carriers in the photo active layer and/or their hindered transport to the respective electrodes.Here, we report the first perovskite-like antimony (V) complex halide with the pseudo-3D crystal structure, which demonstrates EQE of ≈80% and decent power conversion efficiencies close to 4% in planar junction solar cells.While the photovoltaic properties of Sb(III) iodides have been intensively investigated within the last couple of years, halide complexes of Sb(V) remain unexplored. Yet, bromoantimonates (V) or so-called mixed valence complexes containing both Sb(III) and Sb(V) species were first reported more than 70 years ago. [11] These compounds represent intensively colored

most successful to date were complex lead halides comprising simultaneously several univalent cations (Cs + , CH 3 NH 3 + or MA + , [H 2 NCHNH 2 ] + or FA +) and halide anions (typically Br − , I −) in their crystal lattice. [2] However, these materials suffer from low photostability. In particular, Hoke et al. first demonstrated that the mixed-halide MAPb(I 1−x Br x) 3 absorbers undergo rapid light-induced halide segregation with the formation of I-rich and Br-rich phases leading to both structural and energetic disorder resulting in a significant decrease in solar cell performance. [3,4] While the effect of short light exposure was found to be essentially reversible in the dark, long-term irradiation of the mixed halide perovskite films results in their complete degradation. [5] Therefore, light-induced halide phase segregation is considered as a severe limitation for achieving long-term operational stability of perovskite solar cells based on the absorbers incorporating more than a single halide anion. [6] Overcoming this problem is crucially important for the development of tandem devices with the upper cell based on the perovskite absorber with the tailored optical properties realized through halide mixing. Since the discovery of the light-induced halide phase segregation in complex lead halides, many research groups have investigated this phenomenon in detail in an attempt to reveal its mechanism. Multiple models varying in the origin

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