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A π-conjugated small molecule N, N'-bis(naphthalen-1-yl)-N, N'-bis(phenyl)benzidine (NPB) was introduced into poly(9-vinylcarbazole) (PVK) as a hole transport layer (HTL) in inverted perovskite solar cells (PSCs). The NPB doping induces a better perovskite crystal growth, resulting in perovskite with a larger grain size and less defect density. Thus, the VOC, JSC, and FF of the PSC were all enhanced. Experimental results show that it can be ascribed to the reduction of surface roughness and improved hydrophilicity of the HTL. The effect of NPB on the aggregation of PVK was also discussed. This work demonstrates the great potential of PVK as the HTL of PSCs and provides an attractive alternative for HTL to realize high-efficiency PSCs. [ABSTRACT FROM AUTHOR]

A variety of defects exist in the solution-processed polycrystalline perovskites, resulting in photovoltaic output losses and degradation. Chemical interaction is a promising way to realize the passivation of defects. Herein, cetyl pyridinium bromide (CPB) containing both pyridine units and long-chain alkyl groups was introduced in the perovskite precursor solution as a passivation agent. Experimental results show that pyridine unit in CPB formed coordination with uncoordinated Pb2+, which also interact with N–H in MAPbI 3. Meanwhile, long-chain alkyl groups in CPB had interaction with MAI and PbI 2 in MAPbI 3. Thus, trace amount of CPB in the precursor solution improved the optoelectronic properties of perovskite films and suppressed non-radiative carrier recombination in perovskite solar cell (PSC). CPB-modified perovskite films exhibit a lower trap-state density and stronger carrier migration capability. It enables the significant enhancement of PCE values of the p-i-n structured PSC from 18.27 % to 20.53 %, accompanied by the improved stability. Our work exhibits more possibility between passivating additive and PSC performance. [Display omitted] • CPB was introduced in the perovskite precursor solution as a passivation agent. • Pyridine unit in CPB formed coordination with uncoordinated Pb2+. • Long-chain alkyl groups in CPB had interaction with MAI and PbI 2 in MAPbI 3. • CPB-modified perovskite films exhibit a lower trap-state density and stronger carrier migration capability. • A significant enhancement of PCE from 18.27 % to 20.53 % was achieved. [ABSTRACT FROM AUTHOR]

Poly(9-vinylcarbazole) (PVK) is an attractive hole transport layer (HTL) for high efficiency perovskite solar cells (PSCs). But there is still some room for improvement in energy level alignment between the highest occupied molecular orbital (HOMO) of PVK and the perovskite layer. In this work, the solvent of PVK-based HTL was optimized to adjust the energy level of HTLs by changing the volume ratio of chlorobenzene (CB) in dimethylformamide (DMF). Experimental results shows that 20% is the optimal ratio of CB in DMF, based on which the HOMO level of HTL was lifted from −5.62 eV to −5.44 eV. Meanwhile, the morphology of perovskite layer with larger grain size and lower trap density was obtained. As a result, the V OC and J SC of PSCs was enhanced, leading to the increase of PCE from 15.41% to 18.27%. This work paves the way to realize high-efficiency PSCs based on PVK HTL. [Display omitted] • The solvent of PVK-based HTL was optimized to adjust the energy level of HTLs. • The HOMO level of HTL was lifted from −5.62 eV to −5.44 eV. • The V OC and J SC of PSCs was enhanced, leading to the increase of PCE from 15.41% to 18.27%. [ABSTRACT FROM AUTHOR]

Nonradiative recombination losses caused by defects in the perovskite layer seriously affects the efficiency and stability of perovskite solar cells (PSCs). Hence, defect passivation is an effective way to improve the performance of PSCs. In this work, trichloromelamine (TCM) was used as a defects passivator by adding it into the perovskite precursor solution. The experimental results show that the power conversion efficiency (PCE) of PSC increased from 18.87 to 20.15% after the addition of TCM. What's more, the environmental stability of PSCs was also improved. The working mechanism of TCM was thoroughly investigated, which can be ascribed to the interaction between the –NH– group and uncoordinated lead ions in the perovskite. This work provides a promising strategy for achieving highly efficient and stable PSCs. [ABSTRACT FROM AUTHOR]

Nickel oxide (NiOx) has been widely used as a hole transport layer (HTL) of p-i-n type perovskite solar cells (PSCs) because of its many unique properties. However, the poor contact between NiOx and perovskite is disadvantage to the fabrication of high-quality perovskite film, which has bad effect on the open-circuit voltage (V OC), short-circuit current density (J SC) and fill factor (FF) of PSCs. In this report, poly(vinyl alcohol) (PVA) was used as a modifier on the surface of NiOx. Experimental results showed that after PVA modification the PCE of PSCs increased significantly from 16.79% to 19.17% due to the increase of J SC and FF. The MAPbI 3 film on top of the PVA modified NiOx showed larger crystal size, less defect intensity and higher hole mobility. The work mechanism of PVA modification was investigated. This work provides an effective and simple method to improve the performance of PSCs. • PVA modification on NiOx increased the PCE of PSCs from 16.79% to 19.17%. • The film quality of MAPbI 3 was improved after PVA modification. • The wettability of MAPbI 3 precursor solution on NiOx was enhanced. [ABSTRACT FROM AUTHOR]

The energy gap between 6,6-phenyl-C61-butyric acid methyl ester (PCBM) and silver (Ag) is disadvantage to the electron collection of perovskite solar cells (PSCs). In this work, solvent treatment is applied on the surface of PCBM by using ethanol, acetonitrile and ethanol:5 vol% acetonitrile, respectively. Experimental results showed that solvent treatment greatly enhanced the power conversion efficiency (PCE) of PSCs. After ethanol:5 vol% acetonitrile treatment, the PCE of PSC increased from 14.03 ± 0.23 % to 17.03 ± 0.13 % due to the simultaneously enhancement of V OC , J SC and FF. Electronic energy level at the surface of PCBM, electron mobility of PCBM film and the dark current density of PSCs were analysed to investigate the work mechanism of solvent treatment. • Solvent treatment was applied on the surface of PCBM. • The PCE of perovskite solar cells (PSCs) increased from 14.03 % to 17.03 %. • The shift of electronic energy level at the surface of PCBM is mainly responsible for the increase of V OC and J SC. [ABSTRACT FROM AUTHOR]

A high-quality perovskite film is of great significance for efficient and stable perovskite solar cells (PSCs). The use of additives to improve the crystallinity and morphology of perovskite films is an effective way to improve the performance of PSC devices. In this work, 4-carboxyphenyl isothiocyanate (CPIC) was used as an additive in perovskite films to improve the quality of the films. The results of FT-IR showed that the SCN- and -COOH groups with Lewis base in CPIC can coordinate with unpaired Pb2+ on the perovskite films to form Lewis acid-base adducts. The addition of CPIC can effectively improve the crystallinity and grain size of the perovskite films. The results showed that the short circuit current density (J SC) and fill factor (FF) of PSC devices increase significantly with the improvement of film quality, when the concentration of CPIC is 0.5 mg mL−1. These made the efficiency of the devices increase from 16.16 % to 18.19 %. Meanwhile, the introduction of the benzene ring in CPIC can improve the stability of the PSC devices. After aging at room temperature and 50 % humidity for 30 days, the device added with CPIC retained 61.9 % of the initial PCE. This work proves that using CPIC as an additive is an effective method to achieve efficient and stable PSCs. • The Lewis base additive (4-Carboxyphenyl) results in more enhanced PCE up to 18.19 %. • The SCN– and –COOH groups with Lewis base in CPIC can coordinate with unpaired Pb2+ on the perovskite films to form Lewis acid-base adducts. • The addition of CPIC can effectively improve the crystallinity and grain size of the perovskite films. [ABSTRACT FROM AUTHOR]