PSS Hole Transport Layer Research Articles

Large area and flexible CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub> perovskite solar cell fabricated by all ink jet printing

At present, there are many reports on the preparation of large area CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub> perovskite solar cells based on ink-jet printing. These researches focus mainly on the ink-jet printing and electrode printing of perovskite active layer films. The hole transport layer, electron transport layer and other modified layers in the cell structure are still completed by spin coating or coating. In this work, we successfully realize large area CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub> perovskite solar cells based on full ink-jet printing, including pen/Ag NWs bottom electrode, agnws top electrode, PEDOT: PSS hole transport layer, etc. It is found that the full inkjet printing can greatly reduce the material cost and simplify the production process, and obtain PC<sub>61</sub>BM layer, PEDOT: PSS layer, PEI layer and CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub> perovskite thin film with high density and good uniformity. On this basis, we prepare the CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub> perovskite solar cells with areas of 60, 80 and 100 cm<sup>2</sup>, respectively. The results show that when the concentration of perovskite ink is 1 mol/L, the printing speed is 30 mm/s and the substrate temperature is 50 ℃, the surface of perovskite film is smooth and the grain size is in a range of 500–600 nm. The surface roughness of the film is only 10 nm, so high-quality perovskite film can be obtained. The power conversion efficiency of the perovskite solar cell with an effective area of 60 cm<sup>2</sup> is as high as 14.25% (<i>V</i><sub>OC</sub> = 1.03 V, <i>J</i><sub>SC</sub> = 19.21 mA/cm<sup>2</sup>, FF = 72%), which is the highest efficiency of perovskite solar cell prepared by full ink-jet printing method reported so far. In addition, when the device is placed in the air for 12 months without packaging, the photoelectric conversion efficiency is reduced to 80% of the initial value. However, the photoelectric conversion efficiency of FTPU package is reduced only by 5%, demonstrating good device stability.

Improved performance of perovskite light-emitting diodes with a NaCl doped PEDOT:PSS hole transport layer

The effect of the NaCl doping and its implementation in perovskite light-emitting diodes were studied for the first time.

Importance of interface engineering between the hole transport layer and the indium-tin-oxide electrode for highly efficient polymer solar cells

Over 17% efficiency non-fullerene polymer solar cells were achieved by modifying the interface between ITO and a PEDOT:PSS hole transport layer using a conjugated polyelectrolyte (WPFSCz-).

Boosting the performance of planar inverted perovskite solar cells employing graphene oxide as HTL

The numerical simulation tool SCAPS-1D was used to analyze perovskite solar cell having the architecture ITO/ PEDOT:PSS or GO /CH3NH3PbI3-xClx/ PCBM /Au contains inverted planar hetero-junction device. In this work, we investigated the effect of inserting the Graphene Oxide (GO) as Hole Transport layer (HTL) on the performance of perovskite solar cells. Simulation results show that the use of GO as a hole transport layer is efficient. The efficiency of PSCs based on GO HTL was increased by about 1.6 % compared to the conventional PEDOT:PSS HTL device. The obtained results of optimizing the thickness of GO HTL exhibited an optimum value around 10 nm with an efficiency of 12.35 %, Voc of 1.19 V and FF of 54.8 %. We have also shown that the performance of device for high GO carrier density is a better than with low ones. In addition, increasing the temperature beyond the optimum value obtained around 320 K for both HTL materials (GO and PEDOT:PSS) has detrimental effect on the performance of the perovskite solar cells however the device is more sensitive to the temperature with PEDOT:PSS than the GO ones. The effect of band gap of GO on the performance of device is also studied. The obtained results underline the determining role playedby this parameter with an optimum value around 3.25 eV.

Synergetic Effects of Poly(3,4-ethylenedioxythiophene):Poly(styrenesulfonate) with Nanomaterials for Efficient Hole Extracted Perovskite Photovoltaics

Organic-inorganic halide perovskite materials have been touted for their excellent light-absorbing properties, implying great potential for low-cost fabrication of high-performance solar cells. Nevertheless, numerous studies revealed that choice of materials and optimization of device architecture is crucial for realizing high efficiency photovoltaics consisting perovskite photoactive materials. PEDOT:PSS, poly (3,4-ethylenedioxythiophene):poly (styrenesulfonate), has been widely selected as a hole transport material, for its high transparency, which allows enough light to the photoactive layer. However, perovskite solar cells with PEDOT:PSS hole transport layer often suffers low stability, due to the high acidity compared to the other devices.In this research, we introduce various effective solutions for controlling electrical and chemical properties of PEDOT:PSS, for realization of high efficiency and stability of perovskite solar cells. Introducing inorganic copper-based chalcogenide, (such as copper sulfide, Cu2-xS) nanoparticles [1] and organic nanosheets [2] (covalent organic nanosheets, CONs) to PEDOT:PSS hole transport layer resulted in improved charge dynamics factors and device performance. The incorporation of the CuS nanoparticles induced interaction between PEDOT molecules and the particles, which resulted in structural transition of PEDOT:PSS and its higher hole mobility. Interestingly, UV-selective absorbing properties of CuS particles reduced photo-induced damage on perovskite materials, by filtering UV light from the sunlight which enhanced the devices’ stability significantly. On the other hand, the additional organic interlayer between PEDOT:PSS and hole-selective electrode facilitates formation of even film morphology, which contributed to the higher crystallinity of perovskite layers and enhanced charge separation, which resulted in higher performance compared to the pristine device. Suppressing acidity of PEDOT:PSS layer has been another target for enhancing stability of perovskite solar cells. Acidity modification by incorporation of imidazole [3] not only prevented unintentional degradation of device structure, and the PEDOT:PSS with modified pH brought about higher performance which originated from tuned surface properties and molecular rearrangement, which resulted in better crystallization of perovskite coated onto the PEDOT:PSS layers, and efficient charge transport. Also, tailoring ratio of amount of PEDOT to PSS molecules by inducing solution reaction between neutral and acid PEDOT:PSS [4] revealed encouraging electric properties and stability of PEDOT:PSS hole transport layer. This work provides solutions for effective tailoring of electrical and chemical properties of PEDOT:PSS, which will shed light on the low-cost and reliable fabrication of perovskite photovoltaics.[1] Kim, B. G., Jang, W., Choa, Y. H., and Wang, D. H., ACS Sustain. Chem. Eng., 2020, 8, 20, 7617–7627.[2] Park, S., Kim, M. S., Jang, W., Park, J. K., and Wang, D. H. Nanoscale, 2018, 10, 4708-4717.[3] Yi, M., Jang, W., and Wang, D. H. (2019). ACS Sustain. Chem. Eng., 2019, 7, 8245–8254.[4] Kim, M., Yi, M., Jang, W., Kim, J. K., and Wang, D. H. Polymers, 2020, 12, 129.

High-performance and stable inverted perovskite solar cells using low-temperature solution-processed CuNbOx hole transport layer

For a typical perovskite solar cell (PSC), the hole transport layer (HTL) plays a vital role in determining device performance and stability. Herein, for the first time, we demonstrate that a low-temperature solution-processed copper-niobium oxide (CuNbOx) thin film, consisting of CuNbO3 and CuNb2O6 phases, can serve as an efficient HTL to develop PSCs with high-performance and long-term stability simultaneously. The CuNbOx thin film possesses high optical transparency in visible light, well-matched energy levels with perovskite, and excellent hole extraction capability from the perovskite layer. By optimizing the precursor concentration, the CuNbOx-based device reaches the best power conversion efficiency (PCE) of 16.01% with negligible hysteresis. In comparison, the control device based on the extensively studied PEDOT:PSS HTL shows an obviously lower PCE of 10.13%. Besides exhibiting significant improvement in photovoltaic performance, our CuNbOx-based device also shows much enhanced long-term stability than the control device. After 1000 h of storage in air without encapsulation, the CuNbOx-based PSCs maintains ~78% of their initial efficiency, whereas the PCE of PEDOT:PSS-based PSCs drops to ~44% of the initial value. Overall, this study suggests that the utilization of the inorganic CuNbOx thin film as the HTL provides a novel route for fabricating low-cost, high-performance, and stable PSCs.

Sodium Benzenesulfonate Modified Poly (3,4‐Ethylenedioxythiophene):Polystyrene Sulfonate with Improved Wettability and Work Function for Efficient and Stable Perovskite Solar Cells

The p‐type conducting polymer poly (3,4‐ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) is widely utilized as the hole transport layer (HTL) for solution‐processed planar perovskite solar cells (PSCs) with a p‐i‐n structure. However, the inverted PSCs based on PEDOT:PSS HTL suffer from deficient open‐circuit voltage (VOC) and poor stability issues, because of the high electron affinity and acid nature of PEDOT:PSS. Herein, sodium benzenesulfonate (C6H5SO3Na) (SBS) is applied to modify the PEDOT:PSS (SBS–PEDOT:PSS) layer to form a smoother surface and better energy‐level alignment with the perovskite layer. In addition, the SBS–PEDOT:PSS layer with improved hole extraction capacity and suppressed charge recombination, significantly increases the grain size and crystallinity of the MA0.8FA0.2PbI3‐xClx perovskite film. Consequently, the power conversion efficiency (PCE) and VOC of the inverted PSCs are improved from 18.07% and 1.04 V to 19.41% and 1.08 V, respectively, after SBS modification. Moreover, the efficiency of the unencapsulated PSCs based on SBS–PEDOT:PSS remains above 90% after storing in ambient condition for 20 days. This research provides an accessible route to surmount the intrinsic imperfection of PEDOT:PSS and ameliorate the performance of PSCs.

Improved performance of ternary blend polymer solar cells via work function tuning and suppressed interface recombination using hybrid PEDOT:PSS-graphene oxide hole transport layer

In this work, we present a solution-processed poly(3,4-ethylene dioxythiophene):poly(styrenesulfonate)-graphene oxide (PEDOT:PSS-GO) composite as a novel hole transporting material with excellent hole extraction properties which boost the performance of ternary blend polymer solar cells (TPSCs). TPSCs employing ternary blend active layer composed of two conjugated polymer donors i.e., poly(3-hexyl)thiophene):poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b;4,5-b′]dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2–6-diyl)] (P3HT:PTB7-th) blended with organic acceptor [6,6]-phenyl C71-butyric-acid-methyl-ester (PC71BM) have shown high performance when PEDOT:PSS-GO is used as hole transport layer (HTL). The best TPSC, ITO/PEDOT:PSS-GO(1:1)/P3HT:PTB7-th:PC71BM(0.3:0.7:1)/LiF/Al, has showed improved performance with power conversion efficiency (PCE) as high as 7.1% and external quantum efficiency of 70–80% in a broad wavelength range of 350–800 nm. There is an increment of 55% in PCE compared to TPSCs with PEDOT:PSS-only HTL. The improvement in performance of TPSCs with PEDOT:PSS-GO HTLs is predominantly attributed to the better charge extraction and carrier collection owing to significantly reduced photo-generated exciton lifetime, tuned work function, reduced potential barrier at HTL/active layer interface, remarkably improved film morphology, and increased conductivity of PEDOT:PSS-GO films. PEDOT:PSS-GO HTLs significantly boost the performance and lifetime stability of (P3HT:PTB7-th:PC71BM) ternary blend-based TPSCs. Our work demonstrate the superior hole transport properties of PEDOT:PSS-GO over conventional PEDOT:PSS HTLs for the accelerating development of TPSCs.

Intersystem crossing effects on spin mixing in exciplex-based organic light-emitting devices

The electroluminescence (EL) efficiency in exciplex-based organic light-emitting devices (OLEDs) is seriously impacted by the spin sense of injected carriers that leads to spin correlated singlet and triplet polaron pairs, which subsequently form singlet and triplet exciplex, respectively. Magnetic field effect (MFE) measurements have been employed to investigate the intersystem crossing effects on spin mixing induced by hyperfine interaction (HFI), spin-orbit coupling (SOC) and Zeeman splitting on the fraction of singlets formed in the low efficiency exciplex-based OLEDs (electron donor-acceptor, <0.1 cd/A). Poly [ N , N ′-bis(4-butylphenyl)- N , N ′-bis(phenyl)-benzi （Poly-TPD）is selected as electron donor, and 2,5-bis(5- tert -butyl-2-benzoxazolyl) thiophene (BBOT) is used as the acceptor. BBOT: Poly-TPD film is sandwiched between PEDOT: PSS hole-transporting layer and aluminum cathode. In exciplex-based device, a relative larger electron-hole separation distance is obtained because the electrons and holes are located in different neighboring molecules. As a consequence, a small exchange energy ( Δ E S T ) can be achieved by modifying the electron-hole separation distance because the Δ E S T decreases exponentially with increasing its separation distance. We have obtained large (up to ≈ 28.6%) magneto-electroluminescence (MEL) upon the application of a relatively small field, B (<300 mT). In the meantime, its magneto-resistive (MR) exhibits a small value (MR ≈ −2.5%), suggesting that large EL changes are not simply caused by the magneto-resistive effect. Therefore, the external magnetic field influences primarily the radiative exciplex recombination rate but has a negligible effect on the total recombination rate. It is proved that MEL is independent on the reverse intersystem crossing (RISC) spin-mixing mechanism. We show that intersystem crossing (ISC) related spin-mixing process dominates the low efficiency response in the exciplex manifold. The triplet levels are very closer to the singlet level in the ISC process, leading to efficient conversion from singlets to triplets through the HFI and SOC. Therefore, many singlet exciplexes can convert into triplets with thermal energy release, resulting in lower EL efficiency of fluorescent exciplex-based device. • Magnetic field effect (MFE) measurements were used to investigate intersystem crossing effects on spin mixing. • A small exchange energy (△E ST ) can be achieved by separating the HOMO from the LUMO. • A large (up to ≈28.6%) MEL (magneto-electroluminescence) was obtained upon the application of a relatively small field. • Intersystem crossing (ISC) related spin-mixing process dominates the low efficiency response in the exciplex manifold.

Boosting the Efficiency and Stability of Perovskite Light-Emitting Devices by a 3-Amino-1-propanol-Tailored PEDOT:PSS Hole Transport Layer.

Properties of the underlying hole transport layer (HTL) in perovskite light-emitting devices (PeLEDs) play a critical role in determining the optoelectronic performance through influencing both the charge transport and the quality of the active perovskite emission layer (EML). This work focuses on manipulating the carrier transport behavior and obtaining a high-quality EML film by tailoring the poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) HTL with previously unused amino alcohol 3-amino-1-propanol (3AP). The modified PEDOT:PSS rendered a deeper work function that is more suitable for the hole injection from the HTL to EML. More importantly, the 3AP-modified PEDOT:PSS film can induce a low-dimensional perovskite phase that can passivate the defects in the EML, resulting in a significantly improved light emission. Such ameliorations consequently result in a dramatical enhancement in performance of PeLED with a low turn-on voltage of 2.54 V, a maximum luminance of 23033 cd/m2, a highest current efficiency of 29.38 cd/A, a corresponding maximum external quantum efficiency of 9.4%, and a prolonged lifetime of 6.1 h at a proper Cs/Pb ratio.

Improved performance of flexible perovskite light-emitting diodes with modified PEDOT:PSS hole transport layer

We demonstrated the improved device performance of flexible perovskite light-emitting diodes (PeLEDs) on indium-tin oxide coated poly(ethylene terephthalate) (ITO/PET) substrates by using modified poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) as a hole transport layer (HTL). Solvent modification and dopant modification of the PEDOT:PSS solution were carried out by adding isopropyl alcohol (IPA) and poly(sodium 4-styrenesulfonate) (PSS-Na), respectively, to the pristine solution. Devices with the modified HTLs, PEDOT:PSS+IPA and PEDOT:PSS+PSS-Na, exhibited a significant enhancement in both luminance and efficiency. The work function of HTL was improved to reduce the energy barrier against the perovskite layer and facilitate hole transport. The perovskite films deposited on the modified PEDOT:PSS layers showed a uniformly covered surface morphology without any defects, resulting in an increased PL intensity. In particular, the perovskite film coated on the dopant modified HTL showed a better crystallinity and reduced luminescence quenching. The PeLED device with the PEDOT:PSS+PSS-Na HTL exhibited a maximum luminance of 3900cd/m2, a maximum current efficiency of 25.1cd/A, and a maximum external quantum efficiency of 5.9%.

Structural and optical properties of V2O5 nanostructures grown by thermal decomposition technique

Vanadium pentoxide (V2O5) is a widely used industrial catalyst and a promising substitute to the acidic and hygroscopic PEDOT: PSS hole transport layer in organic solar cells. In this work, V2O5 nanostructures were synthesized by thermal decomposition of ammonium metavanadate (NH4VO3) at various temperatures. Structural and morphological studies confirmed the formation of orthorhombic structure of V2O5 nanorods. The UV–Vis–NIR reflectance spectra show a temperature dependent red-shift in band gap corresponding to indirect optical transitions. The peaks corresponding to band edge emissions were obtained from photoluminescence spectra. From Fourier-transform infrared (FTIR) studies, the vibrational modes involved in V2O5 nanostructures were identified. Temperature dependence of the precursor NH4VO3 was evaluated from thermogravimetric–differential (TGA/DTA) curves.

Enhanced performance of polymer solar cells based on P3HT:PCBM via incorporating Au nanoparticles prepared by the micellar method

Surface plasmonic effect of metal nanoparticles is an effective method to improve the power conversion efficiency (PCE) of solar cells. In this work, the PCE of bulk heterojunction (BHJ) polymer solar cells was improved by Au nanoparticles (NPs). The Au NPs were embedded into PEDOT:PSS hole transport layer by spin coating on the ITO substrates. The Au NPs with a diameter of ~16 nm were prepared by the micellar method using polystyrene-block-poly (2-vinylpyridine) diblock polymer. The Au NPs prepared by this method are distributed uniformly in size and without agglomeration on the substrates. From both experimental and theoretical results, it can be seen that the light absorption of the active layer was increased because of the surface plasmonic effect of Au NPs. Meanwhile, the carrier transport performance of PEDOT:PSS was enhanced with introduced Au NPs. As a result, the PCE of BHJ solar cells was improved from 2.81 to 3.25% by incorporating Au NPs.

A Preferential Analysis of Physical Properties in Graphene Oxide Doped PEDOT:PSS Hole Transport Layers

Flexible and semitransparent hole transport layers in perovskite-based photovoltaics have been attracting increasing attention in recent years. Among the benefits they provide, such as being easily reproducible and affordable, they pose their own problems with device degradation, stability, and surface wettability. We probed the graphene oxide doped PEDOT:PSS (GO)/poly(3,4 ethylenedioxythiophene):poly(styrene sulfonate) composite for the application in 2D carbonaceous hole transport layers to improve perovskite solar cells. Advantages and problems are pointed out as well as new perspectives to further modify and retract the drawbacks of conducting polymers. We discussed the advancement of the hole transport layer and described the effects of graphene oxide (dopant) on device transmission, surface wettability, and film quality. Basic principles and mechanisms are covered in the development of polymeric hole transport layers and interfacial properties. Findings included the decrease in device transmission, lessened oxidation of the perovskite, and superior surface wettability. This work highlights the importance and relevance of thin, flexible and powerful photovoltaic systems.

Improved performance of perovskite light-emitting device with urea modified PEDOT:PSS hole transport layer

Efficient perovskite light-emitting devices (PeLEDs) was obtained by tailoring hole transport layer (HTL) PEDOT:PSS with urea. The urea-modulated PEDOT:PSS exhibited better conductivity and deeper work function (WF) compared with the neat PEDOT:PSS, enabling efficient charge injection from the HTL to the perovskite emission layer. The luminescent quenching resulted from the interfacial defects was also effectively suppressed. Such merits consequently result in reduced turn on voltage, promoted brightness, improved current efficiency (CE) and corresponding external quantum efficiency (EQE). By further passivating the bulk defects in the CsPbBr3 films by polyethylene glycol (PEG), a maximum brightness of 26487 cd/m2, a peak CE of 16.68 cd/A and a maximum EQE of 4.84% were achieved.

Light trapping using copper decorated nano-composite in the hole transport layer of organic solar cell

Copper sulphide (CuS) nano-particles were employed in the hole transport layer (HTL) of thin film organic solar cells (TFOSC), to assist in the charge transport processes and improve the photons harvesting. Solar cells were fabricated in the standard bulk heterojunction device architecture using solar absorber composed of poly (3 hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) blend. The CuS nano-particles were dispersed in the aqueous solution of PEDOT:PSS, at concentrations varied from 0% to 0.15% by weight, to be able to determine the right doping level for the best solar cell performances. The particles exhibited surface plasmon resonance absorption and induced intense electric field that was beneficial to exciton dissociation. The highest power conversion efficiency found, in this investigation, was 4.51% at 0.10% CuS concentration in the HTL. This is an increase of 115% and 35% over the pristine PEDOT:PSS and CuS only HTLs used solar cells, respectively. Moreover, the solar cells fabricated with CuS doped PEDOT:PSS hole transport layers exhibited better environmental stability in ambient condition compared to those sole PEDOT:PSS or CuS HTLs. The newly fabricated devices were studied in terms of electrical and optical properties of the solar absorber layers.

Improved performance of lead-tin mixed perovskite solar cells with PEDOT:PSS treated by hydroquinone

Low bandgap lead-tin (Pb-Sn) hybrid perovskite solar cells (PVSCs) have gained a great deal of attentions due to their wide optical absorption range and environmental friendliness. Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is widely used as a hole transport layer for PVSCs. However, the metallic property of PEDOT:PSS causes a barrier at the interface between it and the active layer, thereby hindering the transport of photogenerated carriers. In this paper, in order to eliminate the influence of the interfacial barrier, the PEDOT:PSS surface was treated by hydroquinone (HQ), which lowers the hole transport barrier at the interface, and consequently reduces the interfacial resistance as well. The leakage current in the device with the HQ-treated PEDOT:PSS is significantly reduced, and the surface modification improves the interfacial contact. Compared with the Pb-Sn hybrid PVSCs with the PEDOT:PSS hole transport layer, the power conversion efficiency of PVSCs with the HQ-PEDOT:PSS hole transport layer is improved by 5.7%.

Utilization of poly (4-styrenesulfonic acid) doped polyaniline as a hole transport layer of organic solar cell for indoor applications

The demand for low dimensional, micro powered and wireless indoor electronic devices has been increasing. To power-up those devices, organic photovoltaic (OPV) cells are being employed. The OPV cells exhibit good spectral matching and mechanical flexibility, and can harvest artificial indoor light energy efficiently. Hole transport layer (HTL) is an important component of an OPV cell. Water stable, low temperature processable poly (3, 4-ethylene dioxythiophene): poly (4-styrenesulfonic acid) (PEDOT:PSS) based HTL is commonly used in the indoor OPV cells. However, strongly acidic, highly hydrophilic and expensive PEDOT:PSS resulted in the development of cheaper, mildly acidic and less humidity sensitive alternative hole transport material (HTM) for the indoor OPV cells. Here, we utilized an economical and low acidic, water-stable PSS doped polyaniline (PANI) as HTM for a poly (3-hexylthiophene): [6, 6]-indene-C60 bisadduct (P3HT:ICBA) active material-based indoor OPV cell. The film formed by chemically synthesized PANI:PSS exhibited over 90% transmittance and approximately 5.15 eV work function value. The OPV device exhibited higher shunt resistance and greater power conversion efficiency (PCE) during the operation in an indoor environment. For 1000 Lux white LED light, the device showed around 10% PCE. Furthermore, the device exhibited better stability than PEDOT:PSS HTL based indoor OPV.

Enhanced Charge Transport in Conventional Polymer Solar Cells with a Perovskite-Type LaNiO3 Layer.

In this study, a novel metal oxide, lanthanum nickelate (LNO) with a perovskite structure, was introduced into a polymer solar cell (PSC) device, replacing the PEDOT:PSS hole transport layer (HTL). The results show that the LNO-based PTB7-Th:PC71BM solar cell exhibits a higher circuit current density, power conversion efficiency, and stability compared with a device with PEDOT:PSS HTL. To understand the effect of LNO HTL on the performance of devices, the active layer morphology and charge transport characteristics in PSCs were systematically analyzed. The morphology of active layer was affected by the HTL, which further regulated the generation and transport processes of charge carrier in the PSC device. For the LNO HTL, an appropriate thickness (8 nm) and a small surface roughness (Sq = 0.7 nm) can coordinate the energy-level structure of device and improve the interface contact between the FTO electrode and PTB7-Th:PC71BM active layer, promoting the charge transport performance of device. Therefore, this work provides a new consideration for the preparation of efficient, stable, and low-cost polymer solar cells.

Enhanced stability and efficiency in inverted perovskite solar cells through graphene doping of PEDOT:PSS hole transport layer

Poly(3,4-ethylenedioxythiophene):poly (styrene sulfonate) (PEDOT:PSS) plays a relevant role in the device performance as hole extraction layer (HTL) of inverted perovskite solar cells. Here, we show a simple low-temperature spin coating method for obtaining homogenous graphene-doped thin films of PEDOT:PSS with improved electrical conductivity without decreasing optical transmittance. Moreover, the crystallinity and stability in ambient conditions of the perovskite grown on it are enhanced. The hydrophobic character of graphene probably blocks undesirable reactions hampering degradation. By impedance spectroscopy it is demonstrated better charge extraction and reduction of recombination mechanisms at the doped-HTL/perovskite interface, resulting in improved photovoltaic parameters of the solar cell and greater stability at room operation conditions thus providing a simple and cost-effective method of preparing solar cells based on hybrid perovskites.