In this work, alcohol-vapor solvent annealing treatment on CH₃NH₃PbI₃ thin films is reported, aiming to improve the crystal growth and increase the grain size of the CH₃NH₃PbI₃ crystal, thus boosting the performance of perovskite photovoltaics. By selectively controlling the CH₃NH₃I precursor, larger-grain size, higher crystallinity, and pinhole-free CH₃NH₃PbI₃ thin films are realized, which result in enhanced charge carrier diffusion length, decreased charge carrier recombination, and suppressed dark currents. As a result, over 43% enhanced efficiency along with high reproducibility and eliminated photocurrent hysteresis behavior are observed from perovskite hybrid solar cells (pero-HSCs) where the CH₃NH₃PbI₃ thin films are treated by methanol vapor as compared with that of pristine pero-HSCs where the CH₃NH₃PbI₃ thin films are without any alcohol vapor treatment. In addition, the dramatically restrained dark currents and raised photocurrents give rise to over ten times enhanced detectivities for perovskite hybrid photodetectors, reaching over 10¹³ cm Hz^1/2 W⁻¹ (Jones) from 375 to 800 nm. These results demonstrate that the method provides a simple and facile way to boost the device performance of perovskite photovoltaics.

Efficient conventional bulk heterojunction (BHJ) perovskite hybrid solar cells (pero-HSCs) solution-processed from a composite of CH₃NH₃PbI₃ mixed with PC₆₁BM ([6,6]-phenyl-C61-butyric acid methyl ester), where CH₃NH₃PbI₃ acts as the electron donor and PC₆₁BM acts as the electron acceptor, are reported for the first time. The efficiency of 12.78% is twofold enhancement in comparison with the conventional planar heterojunction pero-HSCs (6.90%) fabricated by pristine CH₃NH₃PbI₃. The BHJ pero-HSCs are further optimized by using PC₆₁BM/TiO₂ bi-electron-extraction-layer (EEL), which are both solution-processed and then followed with low-temperature thermal annealing. Due to higher electrical conductivity of PC₆₁BM over that of TiO₂, an efficiency of 14.98%, the highest reported efficiency for the pero-HSCs without incorporating high-temperature-processed mesoporous TiO₂ and Al₂O₃ as the EEL and insulating scaffold, is observed from PC₆₁BM modified BHJ pero-HSCs. Thus, the findings provide a simple way to approach high efficiency low-cost pero-HSCs.

The surface of the solution-processed methylammonium lead tri-iodide (CH₃NH₃PbI₃) perovskite layer in perovskite hybrid solar cells (pero-HSCs) tends to become rough during operation, which inevitably leads to deterioration of the contact between the perovskite layer and the charge-extraction layers. Moreover, the low electrical conductivity of the electron extraction layer (EEL) gives rises to low electron collection efficiency and severe charge carrier recombination, resulting in energy loss during the charge-extraction and -transport processes, lowering the efficiency of pero-HSCs. To circumvent these problems, we utilize a solution-processed ultrathin layer of a ionomer, 4-lithium styrenesulfonic acid/styrene copolymer (LiSPS), to re-engineer the interface of CH₃NH₃PbI₃ in planar heterojunction (PHJ) pero-HSCs. As a result, PHJ pero-HSCs are achieved with an increased photocurrent density of 20.90 mA cm⁻², an enlarged fill factor of 77.80%, a corresponding enhanced power conversion efficiency of 13.83%, high reproducibility, and low photocurrent hysteresis. Further investigation into the optical and electrical properties and the thin-film morphologies of CH₃NH₃PbI₃ with and without LiSPS, and the photophysics of the pero-HSCs with and without LiSPS are shown. These demonstrate that the high performance of the pero-HSCs incorporated with LiSPS can be attributed to the reduction in both the charge carrier recombination and leakage current, as well as more efficient charge carrier collection, filling of the perforations in CH₃NH₃PbI_3, and a higher electrical conductivity of the LiSPS thin layer. These results demonstrate that our method provides a simple way to boost the efficiency of pero-HSCs.

To develop high-capacitance flexible solid-state supercapacitors and explore its application in self-powered electronics is one of ongoing research topics. In this study, self-stacked solvated graphene (SSG) films are reported that have been prepared by a facile vacuum filtration method as the free-standing electrode for flexible solid-state supercapacitors. The highly hydrated SSG films have low mass loading, high flexibility, and high electrical conductivity. The flexible solid-state supercapacitors based on SSG films exhibit excellent capacitive characteristics with a high gravimetric specific capacitance of 245 F g⁻¹ and good cycling stability of 10 000 cycles. Furthermore, the flexible solid-state supercapacitors are integrated with high performance perovskite hybrid solar cells (pero-HSCs) to build self-powered electronics. It is found that the solid-state supercapacitors can be charged by pero-HSCs and discharged from 0.75 V. These results demonstrate that the self-powered electronics by integration of the flexible solid-state supercapacitors with pero-HSCs have great potential applications in storage of solar energy and in flexible electronics, such as portable and wearable personal devices.

A novel porphyrin-C₆₀ dyad (PCD1) is designed and synthesized to investigate and manipulate the supramolecular structure where geometrically isotropic [such as [60]fullerene (C₆₀)] and anisotropic [such as porphyrin (Por)] units coexist. It is observed that PCD1 possesses an enantiomeric phase behavior. The melting temperature of the stable PCD1 thermotropic phase is 160 °C with a latent heat (ΔH) of 18.5 kJ mol⁻¹. The phase formation is majorly driven by the cooperative intermolecular Por–Por and C₆₀–C₆₀ interactions. Structural analysis reveals that this stable phase possesses a supramolecular “double-cable” structure with one p-type Por core columnar channel and three helical n-type C₆₀ peripheral channels. These “double-cable” columns further pack into a hexagonal lattice with a = b = 4.65 nm, c = 41.3 nm, α = β = 90°, and γ = 120°. The column repeat unit is determined to possess a 129₄₄ helix. With both donor (D; Pro) and acceptor (A; C₆₀) units having their own connecting channels as well as the large D/A interface within the supramolecular “double-cable” structure, PCD1 has photogenerated carriers with longer lifetimes compared to the conventional electron acceptor [6,6]-phenyl-C₆₁-butyric acid methyl ester. A phase-separated columnar morphology is observed in a bulk-heterojunction (BHJ) material made by the physical blend of a low band-gap conjugated polymer, [poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta [2,1-b;3,4-b′]-dithiophene)-alt-4,7-(2,1,3-benzothia-diazole)] (PCPDTBT), and PCD1. With a specific phase structure in the solid state and in the blend, PCD1 is shown to be a promising candidate as a new electron acceptor in high performance BHJ polymer solar cells.