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We introduce BF4− into a wide-bandgap perovskite system to regulate the crystallization dynamics, and the reduced crystallization rate eliminates halogen vacancy defects. The resulting PSC achieves a PCE of 20.09% and improved operational stability.

(1) The defects were passivated and the energy levels aligned at the SnO2/perovskite interface by using EOAI. (2) A champion efficiency of 22.61% was realized for the 1.57 eV PSC and a PCE close to 20% was realized for the 1.68 eV PSC with higher stability.

Compared to fullerene materials, non-fullerene acceptor materials have in recent years been more widely used in organic solar cell devices due to their optical properties and due to the ease of carrying out syntheses to tune their electronic energy levels. Non-fullerene acceptors constitute a major focus of research in the development of bulk-heterojunction organic solar cells. Recent developments have yielded increased power conversion efficiency (PCE) levels for non-fullerene acceptor materials, with the PCE levels now shown to exceed 20%. Perylene diimide (PDI), a non-fullerene acceptor material, has been widely studied because of its good transmission capacity and strong electron affinity. This paper summarizes the application of PDI molecules as acceptor materials in organic solar cells in recent years, detailing the strategies and approaches of molecular design and their application effects.

The electron transport layer (ETL) is of great importance for preparing high-efficiency perovskite solar cells (PSCs). Here we introduced EDTA-2 M (M represents K, Rb or Cs) molecules to stabilize SnO2 colloids, and improve the electrical and surface properties of the SnO2 films. With the help of EDTA-2 M, the electron mobility of SnO2-based perovskite films is increased from 3.6 × 10-4 to 1.27 × 10-3 cm2V-1s−1. In addition, EDTA-2 M molecules can effectively passivate the interface defects of SnO2 and promote the quality of the perovskite films. All the improvements suppress the carrier recombination, leading to a smaller open circuit voltage (VOC) loss. Finally, the 1.57 eV bandgap PSCs based on EDTA-2 M modified SnO2 realized a champion efficiency of 23.30% (VOC = 1.171 V) with a negligible hysteresis, while the 1.69 eV bandgap perovskite device reached an efficiency of 19.76% (VOC = 1.266 V). The unencapsulated PSCs based on EDTA-2 M modified SnO2 only drop 5% of the initial efficiency after being exposed to the ambient atmosphere for 1200 h.

The performance of flexible perovskite solar cells (PSCs) is largely lower than that of their glass/ITO counterparts. This is mainly due to the fact that the surface of PET/ITO is rougher than glass/ITO. ITO bulges could cause the upper perovskite crystals to deteriorate, eventually leading to a large leakage current and the low performance of devices. We reduce the leakage current of PET/ITO assembled PSCs by two measures to improve the PCE of the flexible PSCs. First, double hole transport layers of PEDOT:PSS/NiO are deposited on the surface of PET/ITO, that is, a layer of PEDOT:PSS film is first spin-coated on the ITO surface and then a layer of NiO film is evaporated above to cover the small bulges on the bare ITO. Second, the dual additives of DIO and H2O were introduced to the perovskite precursor solution to control the process of crystal formation and grain growth of the perovskite absorber, finally improving the uniformity and sizes of the perovskite crystals. In conclusion, the double hole transport layers and CH3NH3PbI3−xClx perovskites with dual additives produced a perovskite film with low roughness, high uniformity and large crystal grains on PET/ITO, finally achieving flexible PSCs with the best PCE of 18.0% and excellent flexibility. Our approach provides an effective pathway to fabricate highly efficient and large-scale flexible PSCs.

The recent stunning rise in power conversion efficiencies (PCEs) of ternary organic solar cells (OSCs) has triggered much attention. However, achieving high PCE values are quite challenging because the ternary system is complicated on phase separation behavior. In this work, ternary organic solar cells (OSCs) with one acceptor (PC71BM) and two donors, i.e., one polymer (PTB7-Th) and one small molecule (DR3TBDTT) have been fabricated. We substantially improved PCE from the best reported value of 7.53%–9.25% with increase of 22.8%, and an averaged PCE of 9.25% is obtained due to the improvement of the fill factor (FF) and the short-circuit current density (Jsc). The results of atomic force microscopy (AFM) indicate that a highly ordered molecular compatibility could be obtained by forming alloy with two miscible donors, and the doping of DR3TBDTT not only protects the long distance charge transport in the original binary system, but also improves the size of phase separation of the active layer within the ternary OSCs, thus forming the ordered nano morphology, which can improve the mobility of hole and reduce the charge recombination.

Organic solar cells (OSCs) have emerged as an attractive strategy to efficiently convert light energy into electricity. In this study, the third component 1-bromo-4-nitrobenzene (C6H4BrNO2) was introduced into the active layer of PTB7-Th:PC71BM to promote exciton separation and speed up electron transfer. A PCE of 8.95% was achieved for polymer solar cells (PSCs) with 15 wt% C6H4BrNO2, which is an 18% enhancement in PCE compared with binary OSCs based on PTB7-Th:PC71BM. Atomic force microscopy (AFM) measurements indicated that the ideal morphology can be formed. The charge generation properties were studied in terms of internal quantum efficiency (IQE) and photocurrent density (Jph), revealing that charge transport was facilitated significantly, which favors higher JSC and FF.

In recent years, ternary organic solar cells, which enable extended spectral response range compared to their binary counterpart, have been emerging as an attractive strategy for obtaining impressive photovoltaic properties. In this work, the third component of PBDB-T with a medium bandgap was introduced into PBT7-Th: PC71BM host system to fabricate high efficiency ternary solar cells. It was revealed that PBDB-T not only broadens the light absorption range, but also provides pathway for energy transfer via a Firster resonance energy transfer (FRET) regime. Finally, a champion PCE of 9.45% is achieved for the bulk heterojunction (BHJ) ternary solar cells with 15 wt% PBDB-T, which is 11% enhancement in PCE compared with the host binary OSCs. These results indicate that broadening absorption range is an effective strategy to improve OSCs performance.

A fluorescent inhibitor, 1-Bromo-4-Nitrobenzene (1-Br-4-NB, C 6 H 4 BrNO 2 ), is introduced to poly(3-hexylthiophene) (P3HT)/[6,6]-phenyl-C 61 -butyric acid methyl ester (PCBM) active layer of polymer solar cells (PSCs). When the amount of 1-Br-4-NB added is 25 wt%, the device performance of PSCs is optimal. To investigate the means by which the power conversion efficiency (PCE) is improved, external quantum efficiency (EQE), fluorescence spectrum, transient absorption spectroscopy and dynamics photoresponse, X-ray diffraction (XRD) patterns are measured and density functional theory (DFT) calculations are carried out. The results indicate that excitonic recombination to the ground state is reduced and excitonic dissociation at the donor–acceptor interface is enhanced, which explains the inhibitory effect on the generation of fluorescence. Moreover, the electron transfer complexes (P3HT–C 6 H 4 BrNO 2 ) is demonstrated to be formed after the addition of 1-Br-4-NB. The PCE of PSCs achieves an improvement of more than 57% compared to the reference solar cell without 1-Br-4-NB.

The effects of liquid crystal (LC) reflectors on semitransparent polymer solar cells (PSCs) were investigated in this paper. By improving the cathode, we manufactured semitransparent PSCs based on the conventional PSCs. We then incorporated the LC reflector into the semitransparent PSCs, which increased the power conversion efficiency (PCE) from 2.11% to 2.71%. Subsequently adjusting the concentration and spinning speed of the active layer material changed its thickness. The maximum light absorption for the active layer was obtained using the optimum thickness, and the PCE eventually reached 3.01%. These results provide a reference for selecting LC reflectors that are suitable for different active layer materials to improve the PCE of semitransparent PSCs.

We modified the PEDOT:PSS anode buffer layer in P3HT:PCBM bulk heterojunction polymer solar cells by spin-coating the solvent N,N-dimethylacetamide (DMAC). This modification significantly enhanced the efficiency of the ITO/PEDOT:PSS/DMAC/P3HT:PCBM/LiF/Al solar cells. The DMAC-treated device spin-coated at 3000 rpm exhibited a power conversion efficiency (PCE) of 3.74%, a 59% improvement over that of an untreated cell. To study the mechanism of improving the conversion efficiency, we characterized many parameters, including the light and darkI-Vcurves, external quantum efficiency, active layer absorption spectrum, transmission spectrum of ITO:PEDOTPSS, PEDOT:PSS surface morphology, and electrical conductivity. Modifying the PEDOT:PSS film increased conductivity, making it more conducive to hole extraction and collection. Our findings suggest that modifying the anode buffer layer can improve photoelectric conversion efficiency.