CH3NH3PbI3 Precursor Solutions Research Articles

Spiro-Bifluorene-Cored Dopant-Free Conjugated Polymeric Hole-Transporting Materials Containing Passivation Parts for Inverted Perovskite Solar Cells.

Two spiro-bifluorene-based dopant-free HTMs (X22 and X23) have been synthesized by facilely condensing spiro-bifluorene diamine with 3,4-ethylenedioxythiophene (EDOT)-5,7-dicarbonyl dichloride and 2,3,5,6-tetrafluoro-terephthaloyl dichloride, respectively. In the X22 molecule, lone pairs of electrons on the sulfur (S) and oxygen (O) functional groups interact with the perovskite materials. The hole mobility (μh) of X22 (3.9 × 10-4 cm2 V-1 S1-) is more than twice that of X23 (1.4 × 10-4 cm2 V-1 S1-). The conductivity (σ0) of X22 is 2.73 × 10-4 S cm-1, which is also higher than that of X23 (2.39 × 10-4 S cm-1). The EDOT moiety benefits the contact angle of CH3NH3PbI3 precursor solutions on HTMs as low as 24°. The X22-based device with an indium-doped tin oxide/hole transport material (HTM)/CH3NH3PbI3/phenyl-C61-butyric acid methyl ester (PC61BM)/bathocuproine/Ag structure achieves a power conversion efficiency (PCE) of 19.18%. The PCE of the device based on X23 containing fluorine is 18.70%, and the contact angle between HTM and the perovskite precursor solution is 32°. The X22- and X23-based devices at ambient temperature (≈25 °C) in N2 retain 86% and 79% of the initial PCE after 150 days. The effect of S, O, and F heteroatoms plays an important role in the side chain modification of HTMs, improving defect passivation in HTM/CH3NH3PbI3 interfaces by multiple functional groups.

Carbon quantum dot additive engineering for efficient and stable carbon-based perovskite solar cells

Additive engineering is an effective method to manipulate formation of methyl ammonium metal halide perovskite film for high performance perovskite solar cells (PSCs). In this work, carbon quantum dots (CQDs) prepared from two different carbon sources named as A-CQD and CA-CQD respectively are applied as additives into CH3NH3PbI3 precursor solution via one-step processing. Film morphology and charge transport dynamics of perovskite films with different CQDs additives are investigated. It is found that the A-CQDs incorporated perovskite film has large grain size, excellent crystallinity, enhanced carrier transport ability and high hydrophobic surface. Carbon-based perovskite solar cell using the A-CQD additive shows increased cell performance with the maximum power conversion efficiency (PCE) of 13.28%. While, PCE of the PSCs modified by the CA-CQD additive and without additive are 7.85% and 10.50% respectively. The A-CQD additive modified PSC also presents good long-term stability and maintains more than 90% of its initial PCE after 200 h.

P-type doping in internally photoemitted hot carrier solar cells

Hot carriers in hybrid perovskite have been proven to have eminent properties with long carrier cooling time and long carrier migration distance. The invention of the internally photoemitted hot carrier (IPHC) solar cell recently makes it possible to utilize the hot electrons in CH3NH3PbI3 perovskite and capture their excess energies under steady state illumination. How to further improve the efficiency of IPHC cells is challenging and crucial to demonstrate their effectiveness. In this work, sodium iodide (NaI) is added into the CH3NH3PbI3 precursor solution for inducing a P-type doping and downshifting its Fermi level. The lowered energy barrier at the interface of Au/doped CH3NH3PbI3 promotes the hot electron extraction, thereby enhancing the power conversion efficiency of IPHC devices. The FTO/TiO2/Au/Na+-doped MAPbI3 construction with considerable photocurrent would be an alternative approach for light-to-electricity conversion.

Observation of lower defect density brought by excess PbI2 in CH3NH3PbI3 solar cells

The introduction of excess PbI2 into CH3NH3PbI3 precursors has been reported to boost the efficiency of CH3NH3PbI3 solar cell. It was assumed that the excess PbI2 helped to reduce the defect density in CH3NH3PbI3 solar cell. In this work, by adding non-equimolar PbI2 into CH3NH3PbI3 precursor solution, PbI2-rich CH3NH3PbI3 solar cells have been fabricated. The efficiency of CH3NH3PbI3 solar cell was significantly improved from 14.14% to 16.80%. Results obtained from scanning electron microscopy (SEM) and X-ray diffraction (XRD) indicate that the excess PbI2 does not affect the morphological and crystal properties of CH3NH3PbI3 thin film. Based on time-resolved photoluminescence (TRPL) measurement, it was found that the carrier lifetime of PbI2-rich perovskite thin film was significantly increased. Lower defect density was observed in PbI2-rich CH3NH3PbI3 solar cell by admittance spectroscopy (AS) characterization, indicating PbI2 can suppress the formation of defects in CH3NH3PbI3 solar cells.

N‐type Doping of Organic‐Inorganic Hybrid Perovskites Toward High‐Performance Photovoltaic Devices

The disparity of hole and electron behavior is a ubiquitous issue in methylammonium lead halide perovskites. The carrier mobility imbalance, which will result in a built‐in electric field thus increase the device resistance, is regarded as one of main limiting factors for the further improvement of device performance in perovskite solar cells (PSCs). Here, we realized an n‐doped organic‐inorganic hybrid perovskite by directly incorporating AgI into the CH3NH3PbI3 precursor solution, to fabricate high‐performance PSCs. AgI doping resulted in a balanced charge transporting owing to a remarkable increase in the electron mobility, which was attributed to the aligned orientation of MA+ ions owing to the Ag+‐influenced distribution of electron cloud density. Meanwhile, AgI could act as an additive to control the perovskite crystallization with improved crystallinity and film morphology. Consequently, a maximum power conversion efficiency of over 20% is achieved. The finding in this work provides a direction to fabricate high‐performance PSCs by controlling the charge balance via intensive doping technique.

Highly Reproducible Large-Area Perovskite Solar Cell Fabrication via Continuous Megasonic Spray Coating of CH3 NH3 PbI3.

A simple, low-cost, large area, and continuous scalable coating method is proposed for the fabrication of hybrid organic-inorganic perovskite solar cells. A megasonic spray-coating method utilizing a 1.7 MHz megasonic nebulizer that could fabricate reproducible large-area planar efficient perovskite films is developed. The coating method fabricates uniform large-area perovskite film with large-sized grain since smaller and narrower sized mist droplets than those generated by existing ultrasonic spray methods could be generated by megasonic spraying. The volume flow rate of the CH3 NH3 PbI3 precursor solution and the reaction temperature are controlled, to obtain a high quality perovskite active layer. The devices reach a maximum efficiency of 16.9%, with an average efficiency of 16.4% from 21 samples. The applicability of megasonic spray coating to the fabrication of large-area solar cells (1 cm2 ), with a power conversion efficiency of 14.2%, is also demonstrated. This is a record high efficiency for large-area perovskite solar cells fabricated by continuous spray coating.

Enhanced Photovoltaic Performance of Perovskite Solar Cells by Copper Chloride (CuCl2) as an Additive in Single Solvent Perovskite Precursor

In this letter, we have introduced copper chloride (CuCl2) as an additive in the CH3NH3PbI3 precursor solution to improve the surface morphology and crystallinity of CH3NH3PbI3 films in a single solvent system. Our optimized perovskite solar cells (PSCs) with 2.5 mol% CuCl2 additive showed best power conversion efficiency (PCE) of 15.22%. The PCE of the PSCs fabricated by CuCl2 (2.5 mol%) additive engineering was 56% higher than the PSC fabricated with pristine CH3NH3PbI3.

PVDF-HFP additive for visible-light-semitransparent perovskite films yielding enhanced photovoltaic performance

Organometallic halide perovskite solar cells have considerable potential to be manufactured as low-cost and visible-light-semitransparent modules by reducing the thickness of the perovskite films for building-integrated photovoltaics. However, perovskite films often suffer from voids and roughness, inducing depressed photovoltaic performance, and this problem is even more severe for thinner perovskite films. Herein, a poly(vinylidenefluoride-co-hexafluoropropylene) (PVDF-HFP) additive is incorporated into CH3NH3PbI3 precursor solutions to control the crystal growth of a visible-light-semitransparent perovskite layer (thickness: ~150nm) in a one-step deposition process. The characterization results show that the coverage and smoothness of the perovskite films can be significantly improved, and the perovskite crystal boundaries are also reduced by introducing a moderate amount of PVDF-HFP. When the precursor solution containing 12mg/mL PVDF-HFP, the highest power conversion efficiencies of 10.6% and 8.8% (backward scan) is achieved for the photovoltaic devices with 80 and 20nm-thick Au electrode, respectively, which is over 30% higher than that of the PVDF-HFP-free control. Time-resolved photoluminescence and electrochemical impedance spectroscopy characterizations further demonstrate that the PVDF-HFP additive can improve the carrier lifetimes and reduce the charge transfer resistance, which contributes to the enhanced photovoltaic performance. Thus, we propose a strategy specific to a high-quality visible-light-semitransparent perovskite layer and for high-performance perovskite solar-cell preparation.

Effects of Cl Addition to Sb-Doped Perovskite-Type CH3NH3PbI3 Photovoltaic Devices

The effects of SbI3, PbCl2, and NH4Cl addition to perovskite CH3NH3PbI3 precursor solutions on photovoltaic properties were investigated. TiO2/CH3NH3Pb(Sb)I3(Cl)-based photovoltaic devices were fabricated by a spin-coating technique, and the microstructures of the devices were investigated by X-ray diffraction and scanning electron microscopy. Current density-voltage characteristics and incident photon-to-current conversion efficiencies were improved by a small amount of Sb- and Cl-doping, which resulted in improvement of the efficiencies of the devices. The structure analysis indicated formation of a homogeneous microstructure by NH4Cl addition with SbI3.

Effects of Antimony Addition to Perovskite-type CH3NH3PbI3 Photovoltaic Devices

Effects of SbI3 addition to CH3NH3PbI3 precursor solutions on the photovoltaic properties were investigated. TiO2/CH3NH3Pb1−xSbxI3-based photovoltaic devices were fabricated in air, and formation o...

利用PVP添加剂提高钙钛矿太阳能电池光伏性能

We demonstrate a new one-step solution approach to prepare perovskite CH3NH3 PbI 3films by adding polyvinylpyrrolidone( PVP) to the standard CH3NH3 PbI 3precursor solution. The film morphologies,crystallinities,and optical properties of CH3NH3 PbI 3perovskite layers are carefully studied by SEM,XRD,and UV-Vis. The results reveal that the perovskite film properties can be manipulated by incorporating a small amount of PVP. The absorbance of the film with PVP additive is significantly higher than the pristine film and the absorption peak is red shift by 20 nm,indicating the perovskite film with additive possessing better crystal structures. The use of PVP strongly affects the crystallization process of forming pure CH3NH3 PbI 3and helps the formation of smooth film,leading not only to enhanced crystallization of CH3NH3 PbI 3but also to significantly improved coverage of CH3NH3 PbI 3on a planar substrate. The optimized power conversion efficiency( PCE) of CH3NH3 PbI 3solar cells improved from 1. 30% to8. 38% for the planar cell structure after the addition of 1% mass fraction of PVP. These results suggest that this new one-step solution approach is promising for controlling CH3NH3 PbI 3growth to achieve high-performance perovskite solar cells.