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Among the emerging photovoltaic technologies, rigid perovskite solar cells (PSCs) have made tremendous development owing to their exceptional power conversion efficiency (PCE) of up to 25.7%. However, the record PCE of flexible PSCs (∼22.4%) still lags far behind their rigid counterparts and their mechanical stabilities are also not satisfactory. Herein, we report a highly efficient and stable flexible inverted PSC through modifying the interface between perovskite and hole transport layer (HTL) via Pentylammonium Acetate (PenAAc) molecule. Through synthetic manipulation of anion and cation, we show that the PenA

The discovery of slow hot carrier cooling in hybrid organic–inorganic lead halide perovskites (HOIPs) has provided exciting prospects for efficient solar cells that can overcome the Shockley–Queisser limit. Questions still loom over how electron‐phonon interactions differ from traditional polar semiconductors. Herein, the electron‐phonon coupling (EPC) strength of common perovskite films (MAPbBr3, MAPbI3, CsPbI3, and FAPbBr3) is obtained using transient absorption spectroscopy by analyzing the hot carrier cooling thermodynamics via a simplified two‐temperature model. Density function theory calculations are numerically performed at relevant electron‐temperatures to confirm experiments. Further, the variation of carrier‐temperature over a large range of carrier‐densities in HOIPs is analyzed, and an “S‐shaped” dependence of the initial carrier‐temperature to carrier‐density is reported. The phenomenon is attributed to the dominance of the large polaron screening and the destabilization effect which causes an increasing‐decreasing fluctuation in temperature at low excitation powers ; and a hot‐phonon bottleneck which effectively increases the carrier temperature at higher carrier‐densities. The turning point in the relationship is indicative of the critical Mott density related to the nonmetal‐metal transition. The EPC analysis provides a novel perspective to quantify the energy transfer in HOIPs, electron‐lattice subsystem, and the complicated screening‐bottleneck interplay is comprehensively described, resolving the existing experimental contradictions.

Lead halide perovskite and organic solar cells (PSCs and OSCs) are considered as the prime candidates currently for clean energy applications due to their solution and low-temperature processibility. Nevertheless, the substantial photon loss in near-infrared (NIR) region and relatively large photovoltage deficit need to be improved to enable their uses in high-performance solar cells. To mitigate these disadvantages, low-bandgap organic bulk-heterojunction (BHJ) layer into inverted PSCs to construct facile hybrid solar cells (HSCs) is integrated. By optimizing the BHJ components, an excellent power conversion efficiency (PCE) of 23.80%, with a decent open-circuit voltage (Voc ) of 1.146 V and extended photoresponse over 950 nm for rigid HSCs is achieved. The resultant devices also exhibit superior long-term (over 1000 h) ambient- and photostability compared to those from single-component PSCs and OSCs. More importantly, a champion PCE of 21.73% and excellent mechanical durability can also be achieved in flexible HSCs, which is the highest efficiency reported for flexible solar cells to date. Taking advantage of these impressive device performances, flexible HSCs into a power source for wearable sensors to demonstrate real-time temperature monitoring are successfully integrated.

The demands of sustainable energy sources and depletion of conventional energy sources have accelerated the quest for attaining nontoxic and low‐cost organic solar cells (OSCs). The intrinsic characteristics of organic semiconductor materials such as light weight, mechanical stability, tailorable bandgaps, and ease of solution processability on a large area with flexible devices provide new dimensions to the device engineers toward sustainable electronic technologies. The past two decades have witnessed an inspiring breakthrough of device efficiency by developing multijunction architectures. The significance of organic tandem solar cells (OTSCs) does not only elevate the efficiencies but also considerably reduces the absorption losses. Herein, the recent developments in OTSCs, starting from designing rules for OTSCs, followed by implementation of the interconnecting layer (ICL) structure, and issues regarding processing, light management, and engaging photoactive materials for constructing OTSCs, are comprehensively described. Finally, the conclusion and outlook for OTSCs are provided.

In all kinds of solar cells, transient photovoltage (TPV) decay measurements have been used to determine charge carrier lifetimes and to quantify recombination processes and orders. However, in particular, for thin-film devices with a high capacitance, the time constants observed in common TPV measurements do not describe recombination dynamics but RC (R: resistance, C: capacitance) times for charging the electrodes. This issue has been revisited for organic and perovskite solar cells in the recent literature. Here, these discussions are extended by analyzing a perovskite model system (Bi defects in Cs(0.1)FA(0.9)Pb(Br0.1I0.9)(3) in which defect recombination can be tuned. It is found that TPV, intensity-modulated photovoltage spectroscopy, and impedance spectroscopy yield the same time constants that do not describe recombination dynamics but are limited by the differential resistance of the diode and the geometric capacitance in common light intensity ranges (

CsPbI3 inorganic perovskite has exhibited some special properties particularly crystal structure distortion and quantum confinement effect, yet the poor phase stability of CsPbI3 severely hinders its applications. Herein, the nature of the photoactive CsPbI3 phase transition from the perspective of PbI6 octahedra is revealed. A facile method is also developed to stabilize the photoactive phase and to reduce the defect density of CsPbI3 . CsPbI3 is decorated with multifunctional 4-aminobenzoic acid (ABA), and steric neostigmine bromide (NGBr) is subsequently used to further mediate the thin films' surface (NGBr-CsPbI3 (ABA)). The ABA or NG cation adsorbed onto the grain boundaries/surface of CsPbI3 anchors the PbI6 octahedra via increasing the energy barriers of octahedral rotation, which maintains the continuous array of corner-sharing PbI6 octahedra and kinetically stabilizes the photoactive phase CsPbI3 . Moreover, the added ABA and NGBr not only interact with shallow- or deep-level defects in CsPbI3 to significantly reduce defect density, but also lead to improved energy-level alignment at the interfaces between the CsPbI3 and the charge transport layers. Finally, the champion NGBr-CsPbI3 (ABA)-based inorganic perovskite solar cell delivers 18.27% efficiency with excellent stability. Overall, this work demonstrates a promising concept to achieve highly phase-stabilized inorganic perovskite with suppressed defect density for promoting its optoelectronic applications.

As an indispensable aspect of emerging flexible optoelectronics, flexible transparent electrodes, especially those comprised of metal nanowires, have attracted great attentions recently. Welding the nanowire junctions is an effective strategy for reducing the sheet resistance and improving the operational stability of flexible nanowire electrode in practical applications. Herein, a simple alcohol-based solution approach is proposed to weld crossed silver nanowires by chemically growing silver “solder” at the junctions of the nanowires, forming transparent silver nano-network electrodes with improved electrical conductivity and operational stability. Remarkably, silver nano-networks can be rapidly formed by this simple approach under ambient condition and room temperature, requiring no assistance from heat, light, electrical current, or mechanical pressure. Furthermore, our results show that the nano-network electrode formed from large diameter nanowires offers a better operational stability, whose trend is opposite to that of the untreated electrodes. To demonstrate the potential application of the highly stable silver nano-network from large diameter nanowires, organic solar cells fabricated on the nano-network electrode incorporated with silicon dioxide nanoparticles achieve comparable performance to the ITO control device. Consequently, strategy demonstrated in this work can contribute to low-cost and highly stable transparent electrodes in emerging flexible optoelectronics.

Broadband absorption enhancement in metal nanomaterials for high-performance organic solar cells (OSCs) is highly desirable in the plasmonic-enhanced OSCs. Here, a new dual plasmonic device is proposed by strategically designing device structures and managing two types of plasmonic structures (e.g., metal grating and metal nanoparticles (NPs)) in one device to achieve the broadband enhancement with better reproducibility, including (a) selecting Ag grating with 600 nm period as an anode, (b) introducing metal NPs into the electron transport layer (not active layer), and (c) adopting ZnO as the electron transport layer (not TiO2). The device shows broadband absorption enhancement in the range of 350–800 nm due to multiple plasmonic effects. As a result, the maximum power conversion efficiency (PCE) of 9.62% has been achieved from the device, which is one of the highest efficiencies in plasmonic OSCs reported for a single junction OSC. Importantly, the as-proposed dual device in this work shows an excellent reproducibility of high PCE in experiment, which is much more applicable for practical applications. This work demonstrates the significance of rational design of the device structure and plasmonic nanostructures in achieving high-performance plasmonic OSCs with broadband plasmonic absorption enhancement and reliable reproducibility.

In this paper, over 1.1 eV continuous tuning of metal oxides workfunction is realized by cesium intercalation, making the metal oxide function as both electron transport layer and hole transport layer in organic optoelectronic devices. The demonstrated metal oxides are commonly used molybdenum oxide and vanadium oxide. The proposed approach of synthesizing cesium intercalated metal oxides has interesting properties of room-temperature, ambient atmosphere, water free and solution process, favoring the formation of metal oxides as carrier transport layers at different regions in multilayered devices and large scale fabrication of organic optoelectronics at low cost. Besides the wide range of controllable workfunction adjustment, band structures, and electrical properties are investigated in detail, to understand the effects of cesium intercalation on metal oxides. The device results show that, using the proposed cesium intercalation approach, each of the two investigated metal oxides can function as both ETL and HTL in organic solar cells and organic light emitting diodes with very good device performances. Consequently, with the interesting properties in film synthesis, the proposed cesium intercalated metal oxides can achieve continuously workfunction tuning over a large range and contribute to evolution of the simple route for fabricating high performance organic optoelectronic devices.

Cathode interfacial material (CIM) is critical to improving the power conversion efficiency (PCE) and long-term stability of an organic photovoltaic cell that utilizes a high work function cathode. In this contribution, a novel CIM is reported through an effective and yet simple combination of triarylphosphine oxide with a 1,10-phenanthrolinyl unit. The resulting CIM possesses easy synthesis and purification, a high T g of 116 °C and attractive electron-transport properties. The characterization of photovoltaic devices involving Ag or Al cathodes shows that this thermally deposited interlayer can considerably improve the PCE, due largely to a simultaneous increase in V oc and FF relative to the reference devices without a CIM. Notably, a PCE of 7.51% is obtained for the CIM/Ag device utilizing the active layer PTB7:PC71BM, which far exceeds that of the reference Ag device and compares well to that of the Ca/Al device. The PCE is further increased to 8.56% for the CIM/Al device (with J sc = 16.81 mA cm−2, V oc = 0.75 V, FF = 0.68). Ultraviolet photoemission spectroscopy studies reveal that this promising CIM can significantly lower the work function of the Ag metal as well as ITO and HOPG, and facilitate electron extraction in OPV devices.

Ultraviolet (UV) organic photodetectors (OPDs) operated in the photovoltaic mode, achieving a very high on/off ratio of 105 and a fast response time of 20 ns (a decay time of 888 ns), are demonstrated in this work. Light-induced tuning of the barrier height at the two interfaces of the carrier-extraction layer and light-induced tuning of series resistance are proposed to obtain the high on/off ratio. Fast response of the device is demonstrated through the ultrafast trap filling process. The high on/off ratio and fast response are simultaneously realized by introducing TiO2 nanocrystals as the electron-extraction layer of OPDs. In addition, the good on/off ratio can be maintained in a wide concentration range of 2,2′-(1,3-phenylene)bis[5-(4-tert-butylphenyl)-1,3,4-oxadiazole] (OXD-7) from 25% to 3.75% in the N,N′-bis(naphthalen-1-yl)-N,N′-bis(phenyl)benzidine (NPB):OXD-7 active layer and the corresponding OPDs can also achieve a fast response time simultaneously, good for its practical application. With the optimized device structure, a large detectivity of over 1012 Jones covering the UV-A region (320–400 nm) and a high linear dynamic range of 100 dB are obtained. Additionally, stability of TiO2-based OPDs, which is not well studied but an important parameter for OPDs, is experimentally investigated.

Two of the recent major research topics in optoelectronic devices are discussed: the development of new organic materials (both molecular and polymeric) for the active layer of organic optoelectronic devices (particularly organic light-emitting diodes (OLEDs)), and light management, including light extraction for OLEDs and light trapping for organic solar cells (OSCs). In the first section, recent developments of phosphorescent transition metal complexes for OLEDs in the past 3-4 years are reviewed. The discussion is focused on the development of metal complexes based on iridium, platinum, and a few other transition metals. In the second part, different light-management strategies in the design of OLEDs with improved light extraction, and of OSCs with improved light trapping is discussed.