PCBM Electron Transport Layer Research Articles

Modification of dry/wet hybrid fabrication method for preparing a perovskite absorption layer on a PCBM electron transport layer.

The fabrication method of a perovskite absorption layer on a [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) electron transport layer was investigated for application to perovskite/Si tandem photovoltaic devices. A dry/wet hybrid method that involves thermal evaporation of a PbI2 precursor followed by spin coating of an organic cation solution was found to be a useful means to form a perovskite layer without destruction of the underlying PCBM layer. To form the perovskite layer densely packed with crystals of large grain size and having smooth surface morphology, the rotational speed of the spin coating and the mixing ratio of organic cations were carefully modified. By using this modified absorption layer, a photovoltaic device fabricated under atmospheric exposure conditions showed a power conversion efficiency of ∼10.3% without any large hysteresis. These results have great importance to develop a production technology for high performance tandem solar cells.

Passivation against oxygen and light induced degradation by the PCBM electron transport layer in planar perovskite solar cells

The instability of perovskite solar cells under oxygen and light stress can be alleviated by choosing a suitable device interlayer and device configuration.

Spray coating of the PCBM electron transport layer significantly improves the efficiency of p-i-n planar perovskite solar cells.

The p-i-n structure for perovskite solar cells has recently shown significant advantages in minimal hysteresis effects, and scalable manufacturing potential using low-temperature solution processing. However, the power conversion efficiency (PCE) of the perovskite p-i-n structure remains low mainly due to limitations using a flat electron transport layer (ETL). In this work, we demonstrate a new approach using spray coating to fabricate the [6,6]-phenyl-C(61)-butyric acid methyl ester (PCBM) ETL. By creating a rough surface, we effectively improve the light trapping properties inside the PCBM ETL. We reveal that the spray coated PCBM can form a cross-linked network, which may facilitate better charge transport and enhance extraction efficiency. By improving the contact between the perovskite film and the PCBM ETL, a reduction in the trap states is observed resulting in a PCE increase from 13% to >17%.

Nonconjugated Polymer Poly(vinylpyrrolidone) as an Efficient Interlayer Promoting Electron Transport for Perovskite Solar Cells.

The interfaces between perovskite layer and electrodes play a crucial role on efficient charge transport and extraction in perovskite solar cells (PSCs). Herein, for the first time we applied a low-cost nonconjugated polymer poly(vinylpyrrolidone) (PVP) as a new interlayer between PCBM electron transport layer (ETL) and Ag cathode for high-performance inverted planar heterojunction perovskite solar cells (iPSCs), leading to a dramatic efficiency enhancement. The CH3NH3PbI3-xClx-based iPSC device incorporating the PVP interlayer exhibited a power conversion efficiency (PCE) of 12.55%, which is enhanced by ∼15.9% relative to that of the control device without PVP interlayer (10.83%). The mechanistic investigations based on morphological, optical, and impedance spectroscopic characterizations reveal that incorporation of PVP interlayer promotes electron transport across the CH3NH3PbI3-xClx perovskite/Ag interface via PCBM ETL. Besides, PVP incorporation induces the formation of a dipole layer, which may enhance the built-in potential across the device, conjunctly promoting electron transport from PCBM to Ag cathode and consequently leading to significantly improved fill factor (FF) from 58.98 to 66.13%.

Efficient and highly light stable planar perovskite solar cells with graphene quantum dots doped PCBM electron transport layer

Organic-inorganic hybrid perovskite solar cells (PSCs) have triggered a great deal of research on organic electron transport layers, such as phenyl C61 butyric acid methyl ester (PCBM), due to their potential application as a strong contender in photovoltaic industry with simple fabrication process and low cost. However, the low electrical conductivity and electron mobility of PCBM hinder the promotion of PSCs. Here we report a successful case of graphene quantum dots (GQDs) doping into PCBM electron transport layer (ETL) of planar N-I-P PSCs, resulting in an obvious increase in PCBM conductivity together with the enhanced charge extraction and reduced the trap state density of perovskite films. A low doping ratio (0.5wt%) would be efficient to boost the Voc, Jsc and FF, a PCE of 17.56% is achieved. More importantly, the light stability of PSCs with PCBM: GQDs was improved: the unpackaged cells can keep > 80% of the initial PCE under simulated sunlight with the full UV component present after 300h, in contrast to the reference device that dropped < 50% during the same period of time.

BCP as Additive for Solution-Processed PCBM Electron Transport Layer in Efficient Planar Heterojunction Perovskite Solar Cells

Phenyl-C61-butyric acid methyl ester (PCBM) doped with bathocuproine (BCP) is employed as a novel electron transport layer (ETL) for the first time. We demonstrate that this solution-processed PCBM:BCP blend ETL could significantly improve perovskite solar cell performance in a wide range of BCP doping amounts. The effect of BCP doping has been systematically investigated through a combination of characterizations, including atomic force microscopy, UV–vis absorption spectra, Kelvin probe measurement, surface photovoltage spectroscopy, impedance spectroscopy, and the contact angle test. It is found that the incorporation of BCP not only ameliorates the film formation property of PCBM and the interfacial contact but facilitates the charge transport and separation at the interface through effectively passivating the surface trap states of perovskite as well. As a result, the power conversion efficiency is improved from 7.05% to nearly doubled 13.11%, mainly benefiting from the enhanced short-circuit current density ( J sc) of 18.96 mA/cm2 and fill factor (FF) of 73%. Solution-processed PCBM ETL with BCP as additive endows the devices with excellent performance comparable to or even better than that of traditional devices with evaporated BCP or C60/BCP. It is also an effective and convenient approach to simplify the device fabrication procedure, with promising application in large-scale production.

Enhanced efficiency and air-stability of NiOX-based perovskite solar cells via PCBM electron transport layer modification with Triton X-100.

We modified phenyl-C61-butyric acid methyl ester (PCBM) for use as a stable, efficient electron transport layer (ETL) in inverted perovskite solar cells (PSCs). PCBM containing a surfactant Triton X-100 acts as the ETL and NiOX nanocrystals act as a hole transport layer (HTL). Atomic force microscopy and scanning electron microscopy images showed that surfactant-modified PCBM (s-PCBM) forms a high-quality, uniform, and dense ETL on the rough perovskite layer. This layer effectively blocks holes and reduces interfacial recombination. Steady-state photoluminescence and electrochemical impedance spectroscopy analyses confirmed that Triton X-100 improved the electron extraction performance of PCBM. When the s-PCBM ETL was used, the average power conversion efficiency increased from 10.76% to 15.68%. This improvement was primarily caused by the increases in the open-circuit voltage and fill factor. s-PCBM-based PSCs also showed good air-stability, retaining 83.8% of their initial performance after 800 h under ambient conditions.

Influence of phenyl-C61-butyric acid methyl ester (PCBM) electron transport layer treated by two additives on perovskite solar cell performance

The organic-inorganic metal halide perovskite materials have excellent optical and electrical properties such as high absorption coefficient, high carrier mobility, long carrier lifetime, tunable bandgap, facile fabrication process, etc. Owing to the above excellent properties, the power conversion efficiency (PCE) of perovskite solar cells (PSCs) has increased significantly from 3.8% to 22.1% in the last few years. The PSCs have attracted intensive interest in recent years and show great commercial potential. Previous approaches to increasing the PCE of PSCs have focused on the optimization of the morphology of perovskite film. However, there are relatively few studies on the electron transport layer (ETL) in the typical p-i-n sandwiched structure. In this work, the PCE of PSCs with device structure of ITO/PEDTO: PSS/CH3NH3PbI3/PCBM/Al is improved from 10.8% to 12.5% by using polystyrene (PS) and 1,8-diiodooctane (DIO) as binary additives during the deposition of phenyl-C61-butyric acid methyl ester (PCBM) layer. With the addition of PS, a highly smooth and uniform PCBM ETL is formed due to the increase of viscosity. The morphologies of the PCBM films prepared with and without PS are analyzed using an atomic force microscope in the tapping mode. The root-mean-square surface roughness decreases from 1.270 to 0.975 nm with the addition of PS increasing, which is more effective in preventing electron and hole from recombining at the interface between the perovskite layer and the top electrode. Addition of DIO improves the morphology of PCBM, which plays an important role in charge dissociation, charge transportation, and charge collection. From the time-resolved photoluminescence decay curves of ITO/CH3NH3PbI3/PCBM (with different additives), it is clear to conclude that the exciton dissociation between the perovskite layer and PCBM layer is faster and faster. Electrons and holes can be quickly separated, indicating that charge transport performances of electron transport layer with the addition DIO turn better. The addition of two additives is a simple and low-cost approach to improving the morphology of the electron transport layer, which provides a path-to the further improvement of the performance of p-i-n PSCs.

Efficient and Highly Air Stable Planar Inverted Perovskite Solar Cells with Reduced Graphene Oxide Doped PCBM Electron Transporting Layer

Reduced graphene oxide (rGO) is added in the [6,6]‐Phenyl‐C61‐butyric acid methyl ester (PCBM) electron transport layer (ETL) of planar inverted perovskite solar cells (PSCs), resulting in a power conversion efficiency (PCE) improvement of ≈12%, with a hysteresis‐free PCE of 14.5%, compared to 12.9% for the pristine PCBM based device. The universality of the method is demonstrated in PSCs based on CH3NH3PbI3−xClx and CH3NH3PbI3 perovskites, deposited through one step and two step spin coating process, respectively. After a comprehensive spectroscopic characterization of both devices, it is clear that the introduction of rGO in PCBM ETL results in an important increase of the ETL conductivity, together with reduced series resistance and surface roughness. As a result, a significant photoluminescence quenching of such perovskite/ETL is observed, confirming the increased measured short circuit current density. Transient absorption measurements reveal that in the rGO‐based device, the relaxation process of the excited electrons is significantly faster compared to the reference, which implies that the charge injection rate is significantly faster for the first. Furthermore, the light soaking effect is significantly reduced. Finally, aging measurements reveal that the rGO stabilizes the ELT/perovskite interface, which results in the stabilization of perovskite crystal structure after prolonged illumination.

A PCBM Electron Transport Layer Containing Small Amounts of Dual Polymer Additives that Enables Enhanced Perovskite Solar Cell Performance.

A polymer/PCBM hybrid electron transport layer is reported that enables high-performance perovskite solar cells with a high power conversion efficiency of 16.2% and with negligible hysteresis. Unlike previous approaches of reducing hysteresis by thermal annealing or fullerene passivation, the success of our approach can be mainly attributed to the doping of the PCBM layer using an insulating polymer (polystyrene) and an amine-containing polymeric semiconductor named PFNOX.

Efficiency Enhancement of Inverted Structure Perovskite Solar Cells via Oleamide Doping of PCBM Electron Transport Layer.

An amphiphilic surfactant, oleamide, was applied to dope the PCBM electron transport layer (ETL) of inverted structure perovskite solar cells (ISPSCs), resulting in a dramatic efficiency enhancement. Under the optimized oleamide doping ratio of 5.0 wt %, the power conversion efficiency of the CH3NH3PbIxCl(3-x) perovskite-based ISPSC device is enhanced from 10.05% to 12.69%, and this is primarily due to the increases of both fill factor and short-circuit current. According to the surface morphology study of the perovskite/PCBM bilayer film, oleamide doping improves the coverage of PCBM ETL onto the perovskite layer, and this is beneficial for the interfacial contact between the perovskite layer and the Ag cathode and consequently the electron transport from perovskite to the Ag cathode. Such an improved electron transport induced by oleamide doping is further evidenced by the impedance spectroscopic study, revealing the prohibited electron-hole recombination at the interface between the perovskite layer and the Ag cathode.