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Semitransparent solar cells are promising power-generating windows for building integrated photovoltaics, and the color-fidelity is crucially important for their potential application. Herein, to obtain desirable neutral-colored perception while surmounting the single-junction efficiency barrier, a systematic method is introduced to design semitransparent tandem solar cells (ST-TSCs), and CsPbI2Br/PTB7-Th:IEICO-4F-based perovskite/organic tandem solar cells (P/O-TSCs) with outstanding color-fidelity are first reported. Above all, a numerical method, which includes the fluctuation factor of external quantum efficiency (EQEff) within the visible range to select the front-cell and the absorption selectivity factor within the near-infrared spectrum (SNIR) to assess the rear-cell, is established to construct the device structure. Second, the theoretical transmittance fluctuation factor within the visible range (TFFVIS) and absorption selectivity factor (S) are developed to evaluate ST-TSCs' color-fidelity and photovoltaic performance. Finally, a PTB7-Th layer is introduced to passivate the halogen vacancy defects of CsPbI2Br. As a result, the neutral-colored semitransparent P/O-TSCs with a color coordinate of (0.344, 0.349) are achieved, which possess an efficiency of 13.56%, an average visible transmittance of 26.28% and a color rendering index of 96.4. The synergistic effects of the transmittance fluctuation factor and light-absorption selectivity open the path to design and fabricate semitransparent P/O-TSCs with balanced efficiency and good color neutrality. [ABSTRACT FROM AUTHOR]

Metal halide perovskite light-emitting diodes (PeLEDs) are a new type of electroluminescent device with wide application in flat-panel displays and solid-state lighting. The charge recombination at the electrode interfaces and within the emission layer are the key factors restricting the performance of PeLEDs. In this work, the charge transport layers on both sides of the perovskite are optimized simultaneously to reduce the energy loss at the interfaces. Solution-processed aluminum-doped zinc oxide (AZO) nanoparticles are introduced as the electron transport layer in the traditional device structure, which effectively simplifies the device manufacturing process and greatly improves the device performance. Furthermore, an ultra-thin polymethyl methacrylate (PMMA) layer is introduced as a tunneling layer to reduce the exciton quenching between the hole transport layer and the perovskite emission layer. Poly(2-ethyl-2-oxazoline) (PEOX) is used as an additive to significantly enhance the solvent resistance of the perovskite layer. By collaborative optimization, a deep red PeLED emitting at 683 nm with a turn-on voltage of only 1.6 V and a maximum brightness of 7798 cd m−2 is achieved, providing a new idea for the development of high-performance all-solution-processed PeLEDs. [ABSTRACT FROM AUTHOR]

In recent years, great progress has been achieved in improving the power conversion efficiency (PCE) of organic–inorganic hybrid perovskite solar cells (PSCs), but the stability of PSCs is still an obstacle in their commercialization due to the limitation of efficient and stable hole transport materials. Herein, we demonstrate an alcohol-solution-based low-temperature-processed vanadium oxide (VOx) hole transport layer (HTL) for planar heterojunction PSCs. The good crystallinity and morphology of CH3NH3PbI3 grown on this amorphous VOx film is investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. Due to the suitable and matching energy levels of VOx and CH3NH3PbI3, the holes generated in CH3NH3PbI3 can efficiently transfer to VOx HTL. Furthermore, VOx-HTL-based PSCs yield a PCE value of 14.5% with better stability in comparison with PEDOT:PSS-HTL-based PSCs. These results reveal that the low-temperature-processed VOx films can be employed as the HTL for efficient and stable PSCs. [ABSTRACT FROM AUTHOR]

For bulk-heterojunction polymer solar cells (BHJ-PSCs), appropriate concentration distribution and phase separation of the donor and acceptor molecules within the polymer:fullerene blends are crucial for effective exciton dissociation and charge transportation. Herein, we introduce a selectively dissolvable solvent 2-chlorophenol to finely tune the vertical concentration distribution of fullerene within the photoactive layer. The morphology of the photoactive layer is investigated by atomic force microscopy (AFM), Scanning Kelvin Probe Microscopy (SKPM), transmission electron microscopy (TEM) and water contact angle (WCA) measurements. The optimized three-dimensional concentration distribution is further investigated by time-of-flight secondary-ion mass spectroscopy (TOF SIMS). To investigate the effect of vertical concentration distribution on the photovoltaic performance, conventional and inverted structured PSCs are fabricated. Compared with the control device without modulation of the concentration distribution, the short circuit current density (Jsc) increased from 13.19 to 18.50 mA cm−2 and the power conversion efficiency (PCE) increased from 6.18% to 10.15% for the inverted device with 2-chlorophenol flush treatment due to the greatly enhanced charge transportation and reduced exciton recombination. Our findings indicate that simple 2-chlorophenol flush treatment is a feasible and effective way to acquire an optimal vertical composition profile of photoactive blends for high performance inverted PSCs. [ABSTRACT FROM AUTHOR]

Improving the light absorption of the photoactive layer is a key issue to enhance the photovoltaic performance of polymer solar cells (PSCs). Herein, the transfer-matrix method is used to model the absorption spectra and optical electric field distribution within the multilayer stack of conventional and inverted PSCs based on PBDTTT-C-T:PC70BM blends. The simulation results show that the short-circuit current density (Jsc) of the devices increases with increasing photoactive layer thickness and an oscillation can be observed for both conventional and inverted devices. By applying an inverted architecture, higher optical electric field energy dissipation in the photoactive layer can be realized, and higher Jsc can be achieved. Guided by the simulation results, high performance conventional and inverted PSCs based on PBDTTT-C-T:PC70BM are experimentally fabricated. Comparing the external quantum efficiency (EQE) with the absorption spectra for both devices, the increased Jsc for the inverted device is attributed mainly to the enhanced absorption. The conventional device shows a power conversion efficiency (PCE) of 7.09%, while the inverted device shows enhanced Jsc and FF, and the PCE reaches 8.81%, which is increased by 24.3% in comparison with that of the conventional device. The agreement between the modeling and experimental results confirms the directive function of optical modeling on device design and optimization. [ABSTRACT FROM AUTHOR]

PEDOT-PSS is a widely used hole extraction layer in polymer solar cells (PSCs). However, its acidic and hygroscopic nature usually affects the long-term stability of photovoltaic devices. Herein, we report an effective method to enhance the conductivity and stability of the PEDOT-PSS film by doping with an amphiphilic perfluorosulfonic copolymer, Nafion. The highly hydrophobic fluorocarbon backbone of Nafion preferentially interacts with the hydrophobic PEDOT of PEDOT-PSS, while the highly hydrophilic –SO3H groups preferentially interact with hydrophilic PSS chains, inducing the PEDOT chains to separate from the PSS chains by Nafion. The conductivity and surface morphology of the Nafion-doped PEDOT-PSS layer were investigated by using a four-point probe and an atomic force microscope, respectively. The optical properties of the Nafion doped PEDOT-PSS film and the photoactive layer spin-coated on it were studied by transmittance and reflection spectra. With the Nafion doped PEDOT-PSS hole extraction layer (HEL), the power conversion efficiency of the PSCs based on poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) reaches 4.63%, increased by 14.3% in comparison with that of the control devices. Furthermore, the lifetime of the devices with Nafion doped PEDOT-PSS HEL is greatly enhanced. [ABSTRACT FROM AUTHOR]

A new method is developed to prepare RuO2 films through UVO treatment of solution-processed ruthenium(iii) acetylacetonate (Ru(acac)3) without thermal annealing. By introducing RuO2 as an anode buffer layer, highly efficient polymer solar cells (PSCs) have been achieved. The resultant RuO2 layer exhibits high light transmittance in the visible range. Remarkable improvements in the short-circuit current density (Jsc) of the PSCs can be achieved upon the introduction of the RuO2 buffer layer. The PSCs with the RuO2 anode buffer layer demonstrate improved photovoltaic performance in comparison with the devices using poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) as the anode buffer layer. The power conversion efficiency (PCE) of the PSCs based on P3HT:PCBM and P3HT:ICBA reaches as high as 4.19% and 7.07%, respectively. An even higher PCE of 7.45% is realized by adopting a new conjugated polymer, PBDTBDD, as the donor. The results demonstrate that RuO2 has great potential as a hole collection material for highly efficient PSCs. [ABSTRACT FROM AUTHOR]

Application of a hydrostatic pressure in the range of 1-650 atm boosted photoluminescence and electroluminescence of hexaphenylsilole by approximately 10 and approximately 73%, respectively, due to the suppression of intramolecular rotations and/or the increase in carrier injection, offering a helpful mechanistic insight into the intriguing phenomenon of aggregation-induced emission.