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The composite high‐performance electrode is very important for excellent photoelectric devices. Interfacial modification is the dominating method to optimize electrode properties. Two easily synthesized perylene monoimide (PMI)‐derived organic phosphonium bromide salts are found interestingly valuable when they are applied as cathode interlayers (CILs) in bulk heterojunction (BHJ) organic solar cells (OSCs). Using the PBDB‐T:ITIC blend as the BHJ active layer in the inverted device structure, the power conversion efficiency (PCE) is greatly improved from 9.49% of the referenced device, which is without phosphonium CIL, to a PCE of 10.42% with PMI‐triphenyl‐phosphonium bromide (PMI‐TPP) and a PCE of 9.87% with PMI‐trimethoxylphenylphosphonium bromide (PMI‐TMOPP) as the CIL. Moreover, the two organic phosphonium bromide salts are also investigated by the traditional device structure, the PCE is 4.21% for the bare aluminum cathode referenced device, in contrast with a moderate increased PCE of 5.18% with PMI‐TPP CIL or a PCE of 5.05% with PMI‐TMOPP CIL. Therefore, the organic phosphonium bromide salt PMI‐TPP is a promising candidate of CIL material in OSCs. [ABSTRACT FROM AUTHOR]

Carbon-based perovskite solar cells aroused huge attention for their simple, low-cost device fabrication processing and excellent stability. However, the fully low-temperature preparation and flexibility of carbon-based perovskite solar cells remain huge challenges. Here we demonstrate the fabrication of carbon-based perovskite solar cells processed at fully low-temperature, which take thermally evaporated cadmium sulfide as efficient electron transport layer, and obtain an optimal power conversion efficiency of 13.22%. With the decoration of PCBM, the separation of charges at the interface is facilitated and the recombination is hindered, so a higher fill factor is obtained and the efficiency is further improved to 14.28%. Our devices also exhibit good long-term durability and excellent ultraviolet stability. Based on the fully low-temperature preparation process, carbon-based flexible devices are further developed with an optimal efficiency over 9% and considerable mechanical stability, which can serve as the roof-top photovoltaics and power sources for wearable devices. Image 1 • Fully low-temperature processed and flexible carbon-based PSCs with excellent efficiency and stability are demonstrated. • First use of CdS as electron transport layer for carbon-based PSCs. • With the decoration of PCBM, efficiency of the best-performing device is greatly enhanced. [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]

The possible exhaustion of fossil fuels in the near future and soaring global energy demand have driven the search for new types of sustainable and renewable alternatives. Perovskite (CHNHPbX, X = I, Br, Cl) solar cells are a type of solar cell based on a perovskite absorber, most commonly a tin halide-based or hybrid organic-inorganic lead material, as the visible-light sensitizer layer, which produces electricity from sunlight. Recently, perovskite solar cells have received substantial worldwide attention. Compared with traditional solar cells, the perovskite solar cells can obtain high efficiency with a simple architecture and via a cost-effective process. In the latest 5 years, the efficiency of perovskite solar cells to convert power has skyrocketed from 3.8 % to more than 19.3 %. It is the fastest advancing solar technology to date. The highest efficiency demonstrated by perovskite solar cells is higher than that of dye-sensitized solar cells (DSSCs). A lager number of research groups have demonstrated that perovskite solar cells may ultimately boost efficiency as high as 25 %. The high efficiency and cheap production costs make it evident that perovskite solar cells have great potential to be commercialized soon. In this review, the history, materials, processing and architecture of solar cells are discussed to obtain a better understanding of high-performance perovskite solar cells. [ABSTRACT FROM AUTHOR]