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• Double modification – simultaneously using MoS 2 as buffer layer and additives. • MoS 2 film acts as a protective and ideal electron blocking candidate. • MoS 2 doped CH 3 NH 3 PbI 3 , enhance the quality of the perovskite film. • CH 3 NH 3 PbI 3 : MoS 2 heterojunction promote charge transfer. Organic-inorganic perovskite solar cells emerge as one of the most promising photovoltaic technology due to its high performances. Particularly, inverted perovskite device architecture, due to low temperature processing, have a great potential in commercialization. High-crystalline quality perovskite film and interfacial passivation are essential to yield high performance devices. In this work, we employ a simple strategy of using molybdenum disulfide (MoS 2) as both the interfacial layer and the additive to prepare efficient PSCs. MoS 2 as an additive in perovskite can form the CH 3 NH 3 PbI 3 :MoS 2 heterostructure, resulting in the homogeneous perovskite film with larger crystal grains. In addition, MoS 2 as the buffer layer (BL) between poly (3,4-ethylene dioxythiophene)-poly (styrene sulfonate) (PEDOT:PSS) and perovskite can prevent the decomposition of perovskite film by avoiding the direct contact with the hydrophilic PEDOT:PSS films. On tedious optimization, the champion device based on active layer of CH 3 NH 3 PbI 3 :MoS 2 (10 v%) as well as employing MoS 2 buffer layer shows a remarkable improvement in the power conversion efficiency (PCE) (from 15.29% to 18.31%) and a better stability, with 87% of the initial efficiency sustained after 20 days. Our finding herein provides a promising way to fabricate high efficiency and stable photovoltaic devices. [ABSTRACT FROM AUTHOR]

Abstract Organic-inorganic lead halide perovskite solar cells have garnered enormous interest in scientific communities due to comparable power conversion efficiencies and solution-processed fabrication techniques. Among them, carbon-based perovskite solar cells seem to be one of the most promising candidates for addressing the stability issue while suffering from inferior efficiency or high processing temperature. Herein, we introduce low-temperature processed Zn-doped SnO 2 (below 200 °C) as an effective electron transport layer in perovskite solar cells for the first time, and demonstrate a low-temperature carbon-based device with Cu-phthalocyanine as hole transport layer. We find that Zn doping contributes to a more suitable energy level alignment and an improved conductivity for SnO 2 films. As a result, the electron transfer and extraction are enhanced and the charge recombination is suppressed. In addition, devices with Zn-doped SnO 2 have a wider depletion region, leading to an enhanced photovoltaic performance. An optimal efficiency of 17.78% can be obtained after 2 mM Zn doping. Furthermore, these devices, introducing highly stable and hydrophobic Cu-phthalocyanine and carbon, maintain almost 100% of their initial efficiencies over 1200 h in ambient air. Our study paves the way for developing highly efficient and flexible carbon-based perovskite solar cells. Graphical abstract 17.78% efficient low-temperature carbon-based planar perovskite solar cell using Zn-doped SnO 2 electron transport layer is demonstrated. Zn doping contributes to a more favorable energy level alignment, an improved conductivity and a wider depletion region, resulting in an enhanced performance. The low-temperature and solution process realize flexible perovskite solar cells. Unlabelled Image Highlights • A high efficiency of 17.78% is achieved among carbon-based perovskite solar cells. • The whole process is conducted at low temperature (below 200 °C), enabling the fabrication of flexible devices. • The low-temperature processed Zn doped SnO 2 is introduced as an electron transporting layer in perovskite solar cells. • Excellent stability is obtained by utilizing CuPc and Carbon as hole transporting layer and electrode. [ABSTRACT FROM AUTHOR]

Abstract Fullerenes have been widely used as the electron transport layers (ETL) for planar-heterojunction perovskite solar cells (PSCs), due to their superior abilities in electron transporting, hysteresis suppression and low-temperature processing. Here, we demonstrate a novel inverted PSC with evaporated C 60 as ETL and dopant-free copper phthalocyanine (CuPc) as hole transport layer (HTL). The C 60 ETL can not only transport photogenerated electrons, but also passivate grain boundaries and surfaces of perovskite films effectively. By optimizing the thickness of the C 60 ETL, a champion power conversion efficiency (PCE) of 16.72% is obtained with almost no hysteresis and less than 10% decay in efficiency is observed during a two-week stability test. To the best of our knowledge, this is the highest efficiency of the inverted PSCs employing CuPc as HTL. For comparison, the devices using PCBM as ETL are also prepared and only achieve a highest efficiency of 15.74%. Various characterizations and analyses attest the enhanced charge transport and extraction as well as suppressed charge recombination and hysteresis for the C 60 -based devices. Since all the processes are accomplished under a low temperature, this enable us to fabricate flexible PSCs on polyethylene terephthalate (PET) substrates with a highest PCE of 12.96%. Our work provides a new strategy for fabricating cost-effective, highly efficient and hysteresis-free flexible PSCs in mass production. Graphical abstract Novel efficient C 60 -based inverted perovskite solar cells with negligible hysteresis are demonstrated. A champion power conversion efficiency (PCE) of 16.72% and 12.96% is obtained for the devices prepared on rigid and flexible substrates, respectively. Image 1 Highlights • Novel inverted perovskite solar cells (PSCs) with Cu-phthalocyanine and C 60 as HTL and ETL, respectively. • 16.72% efficiency is obtained, which is the highest efficiency of the inverted PSCs employing CuPc as HTL. • 12.96% efficiency is obtained for the flexible device. • Almost no hysteresis is observed. • Cost-effective, easy to prepare and highly stable. [ABSTRACT FROM AUTHOR]

Electron transport layer (ETL), functioning as the electron transportation and extraction layer as well as hole-blocking layer, plays an important role in planar perovskite solar cells (PSCs). Majority of the state-of-the-art PSCs contain a TiO 2 ETL always requiring a high temperature (500 °C) treatment, which is both energy-consuming and incompatible with flexible substrates, thus hindering large-scale application in flexible devices. Here, we demonstrated a low-temperature (70 °C) solution-processed Mg-doped rutile TiO 2 as ETL in planar PSCs, while the thermal-evaporated copper phthalocyanine (CuPc) and doctor-bladed carbon were introduced as the hole transport layer (HTL) and counter electrode, respectively. The as-prepared PSC obtains a 15.73% power conversion efficiency (PCE), which is quite an excellent efficiency among carbon-based planar PSCs, getting an increase by 16% compared to the 13.56% PCE of the pristine TiO 2 -based device. The prominent increment is mainly attributed to the faster charge extraction, better electrical conductivity and suppressed charge recombination of Mg-doped TiO 2 . Besides, using highly stable CuPc and commercial carbon makes the as-prepared PSCs highly durable over 30 days when exposed to the ambient air with a relative humidity of 50%. Since all the processes are conducted under 100 °C, our work paves a way for developing cost-effective and highly stable PSCs compatible with flexible substrates. [ABSTRACT FROM AUTHOR]

In this work, an efficient and stable inverted planar perovskite solar cell (PSC) with water additive has been prepared in ambient air. Adding moderate water additive to CH 3 NH 3 PbI 3−x Cl x precursor solution leads to growth in quality of CH 3 NH 3 PbI 3−x Cl x film, because the boiling point of water is lower than that of N, N-dimethylformamide. The annealing temperature of the CH 3 NH 3 PbI 3−x Cl x film is controlled to 105 °C (slightly higher than the boiling point of water) to obtain the dense perovskite film rapidly in ambient environment with ~ 40% relative humidity. The highest power conversion efficiency (PCE) of PSC with water additive is 14.02%, higher than that (11.17%) of the reference device without water additive. In addition, the aqueous CH 3 NH 3 PbI 3−x Cl x solution is transformed into the stable perovskite film through the method of rapid annealing. The stable CH 3 NH 3 PbI 3−x Cl x ·nH 2 O system can resist the decomposition of perovskite film and weaken iodide ion migration in PSCs, which enhance stability of the device under the atmospheric environment. After being stored in the air for 120 h, the PSC device with water additive still has an PCE of 12.01%, higher than that (1.64%) of the reference device. [ABSTRACT FROM AUTHOR]

Planar-structure perovskite solar cells have attracted more and more attention, because their simple and low-temperature preparation processing. However, the performance of perovskite solar cells is currently limited by defect-induced recombination at interfaces between perovskite and charge transport layers. In this work, a filmy poly methyl methacrylate (PMMA) layer introduced in Perovskite/Spiro-OMeTAD interface to passivate the interfacial and interganular defects, by which a high open-circuit voltage (1.18 V) is acquired, and the optimal device shows a steady-state power conversion efficiency of 20.5% and negligible hysteresis. Femtosecond transient absorption measurement confirms a significant reduction in non-radiative recombination for passivated devices. Mott-Schottky measurement indicates improved flat band potential and carrier density in passivated devices, consisting with the increased voltage. In addition, PMMA film can protect perovskite film from moisture and oxygen erosion. The unsealed device still maintains 95% of the initial efficiency under ambient conditions with 60% relative humidity for one month. This approach solves one of the main limitations of interfacial recombination and shows its potential to improve the performance of perovskite solar cells in the future. • An ultrathin polymer film is used to passivate the interfacial and intergranular defects in PSCs. • The modified PSC shows a steady-state power conversion efficiency of 20.5% and negligible hysteresis. • The fs-TA measurement is implemented for analyzing transfer and recombination dynamics of the photo-generated carrier. • The PMMA film plays the role of encapsulation which could protect perovskite film from moisture and oxygen erosion. [ABSTRACT FROM AUTHOR]

All-inorganic CsPbBr 3 perovskite has triggered great interests in photovoltaic field owing to its superior stability. However, the uncontrollable CsPbBr 3 film growth in solution always leads to a poor film quality with low phase-purity as well as many surface and bulk defects. Herein, we demonstrate an environmentally friendly non-solution route to fabricate high-quality CsPbBr 3 films for carbon-based planar perovskite solar cells. By precisely tuning the thickness ratio of the evaporated CsBr to PbBr 2 precursors (r), the dominant phase conversion of the cesium lead bromide perovskites from PbBr 2 -rich CsPb 2 Br 5 (r ≤ 12:7) to CsPbBr 3 (r = 12:8), and further to CsBr-rich Cs 4 PbBr 6 (r ≥ 12:9) are achieved. The optimized CsPbBr 3 perovskites are highly phase-pure and crystallized with ultra-high light absorption ability. The as-prepared CsPbBr 3 films also exhibit a dense and uniform morphology with large grain sizes and monolayer-vertical aligned grains. The corresponding devices deliver a champion PCE of 7.58%, which is an excellent efficiency among carbon-based CsPbBr 3 cells with evaporated CsPbBr 3 light absorbers. The large-area (1 cm2) devices also achieve an efficiency of 6.21%. Moreover, the unencapsulated CsPbBr 3 devices present superior moisture and thermal stabilities. Our work provides a facile approach to fabricate high-quality and large-area CsPbBr 3 films for highly efficient solar cells, light-emitting diodes and photodetectors. Image 1 • A sequential evaporation method is devised to prepare high-quality CsPbBr 3 films. • An excellent PCE of 7.58% is achieved for carbon-based CsPbBr 3 PSCs. • A PCE of 6.21% is obtained for large-area devices with an active area of 1 cm2. • Superior moisture and thermal stabilities are obtained for the devices. • The whole production costs of the devices are very low. [ABSTRACT FROM AUTHOR]