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The quality of perovskite films plays a fundamental role in determining the performance of perovskite solar cells (PSCs). It is widely recognized that achieving high crystalline quality and minimizing defect density in perovskite films are essential. In this study, the utilization of the multifunctional additive 5‐ammonium acid (5‐AVA) to improve the morphology of perovskite films is proposed. The ‐NH2 and ‐COOH groups in 5‐AVA enable effective coordination with Pb ions and organic ions in perovskite, resulting in the suppression of defect formation and the reduction of non‐radiative recombination losses. Furthermore, the addition of 5‐AVA facilitates a more favorable energy level alignment, thereby enhancing the transfer of carriers between the perovskite layer and transport layers. Consequently, this process contributes to the improvement of the open circuit voltage (VOC) in PSCs. Attributing to the addition of 5‐AVA, the optimized PSCs achieve significantly enhanced performance with a maximum photoelectric conversion efficiency (PCE) of 24.74% and excellent long‐term stability. This work presents a straightforward and effective approach to enhance the performance and long‐term stability of PSCs. [ABSTRACT FROM AUTHOR]

The performance of perovskite solar cells is greatly affected by the crystallization of the perovskite active layer. Perovskite crystal grains should neatly arrange and penetrate the entire active layer for an ideal perovskite crystallization. These kinds of crystallized perovskite films exhibit fewer defects and longer carrier lifetime, which is beneficial to enhance the performance of perovskite solar cells. Here, by testing the residual charge of perovskite solar cells with different crystallization conditions, it is demonstrated that the residual charge exists widely at the grain boundary, which is parallel to the device, and the residual charge is related to the performance of the perovskite solar cells. Single crystal grains neatly arranged and penetrate the entire active layer can generate less residual charge and improve device performance of the perovskite solar cells. The results also show that the long decay time of open‐circuit voltage comes from the detrapping of trapped carriers. The residual charge testing technology provides a new idea for the investigation of carrier trap and detrap characteristics in photovoltaic devices. [ABSTRACT FROM AUTHOR]

Multinary copper chalcogenide semiconductor nanocrystals (NCs) have achieved increased attention due to their lessened toxicity and compositional versatility as well as their outstanding optical properties and optoelectronic applications in light‐emitting diodes (LEDs) and solar cells. Herein, the synthesis of highly luminescent multinary Cu‐In‐Zn‐S semiconductor NCs with tailored nanostructures, which exhibit the best absolute photoluminescence quantum yield of 90%, is presented. The tailored nanostructures are realized through the variation of the dosage and injection speed of Zn precursors, which determine the balance between Zn2+ cation diffusion and ZnS shelling reaction. The depth profile measured using X‐ray photoelectron spectroscopy reveals the gradient distribution of Zn elements from core to surface in the samples synthesized using higher feeding amounts of Zn precursors in a one‐pot method, which favors the formation of a soft core/shell structure. Time‐resolved spectroscopic studies confirm that the inward diffusion of Zn2+ and overcoating of a ZnS shell could reduce the number of intrinsic internal or surface defects, finally inducing a near‐unity radiative decay of excitons in single recombination pathway. As a demonstration, the highly luminescent multinary Cu‐In‐Zn‐S semiconductor NCs are incorporated into LEDs and a white light‐emitting diode is accessed through a two‐component strategy. [ABSTRACT FROM AUTHOR]

In this work, the effects of solvent additives on the trapping and recombination of carriers in polymer solar cells based on the blend of poly(3-hexylthiophene) (P3HT) and indene-C60-bisadduct (ICBA) are investigated by measuring the ideality factor and transient photocurrent. The addition of a few percent of 4-bromoanisole (BrAni) and 1-chloronaphthalene (CN) can give rise to the preferable morphology with well-ordered interpenetrating networks, which is beneficial for charge transport. Efficiency enhancement of polymer solar cells with solvent additives originates from the decreased defects and suppressed trap-assisted recombination at the interface between the donor and acceptor materials. [ABSTRACT FROM AUTHOR]

ABSTRACT We investigated the reduction in the absorption intensity of poly(3-hexylthiophene) (P3HT) in a poly(3-hexylthiophene)/(6,6)-phenyl-C61-butyric acid methyl ester (P3HT/PCBM) 'bilayer' heterojunction film that was fabricated using orthogonal solvents. The results show that even though P3HT is insoluble in dichloromethane (DCM), DCM could decrease the chain packing and the crystallinity of the P3HT film by the swelling effect. DCM also assists in the penetration of the PCBM into the P3HT underlayer during spin-coating. After the DCM evaporates, the PCBM in the P3HT matrix hinders the self-reorganization of P3HT, causing a drop in the absorption intensity of P3HT. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41757. [ABSTRACT FROM AUTHOR]

In this work, the effects of photo-induced defects on polymer solar cells (PSCs) based on the blends of poly (4,8-bis-alkyloxybenzo (1,2-b:4,5-b′) dithiophene-2,6-diyl-alt-(alkyl thieno(3,4-b) thiophene-2-carboxylate)-2,6-diyl) (PBDTTT-C) and [6,6]-phenyl C70-butyric acid methyl ester (PC70BM) are investigated. In addition to conventional PSC characterization approaches, the capacitance-voltage ( C-V) response and the ideality factor are used to analyze the changes in the built-in potential and defect-induced recombination at the internal donor/acceptor interface and the electrode interfaces in illuminated PSCs. The results show that the dominant trap states increase with increasing illumination time, which indicates that photo-induced defects play an important role in the photodegradation of inverted PSCs. (© 2015 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

In this study, large-sized silver nanoparticles (Ag NPs) (average size: 80 nm) have been introduced into the anodic buffer poly-(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) layer (thickness: about 55 nm) of poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester bulk heterojunction polymer solar cells. The results showed that the short-circuit current density can increase from 8.73 to 11.36 mA/cm, and power conversion efficiency increases from 2.28 to 2.65 % when 0.1 wt% Ag NPs was incorporated in PEDOT:PSS layer, corresponding to an efficiency improvement of 16.2 %. Absorption spectrums of the active layers indicate that large-sized Ag NPs have no clear contribution to optical absorption improvement. By measuring the conductivity of PEDOT:PSS films without and with Ag NPs and analyzing device structure of this polymer solar cell, it was founded that the improvements in power conversion efficiency was originated from higher conductivity of PEDOT:PSS layer incorporated with Ag NPs and the shorter routes for holes to travel to the anode. [ABSTRACT FROM AUTHOR]

Discrete SnO2 Nanoparticle-Modified Poly(3,4-Ethylenedioxythiophene):Poly(Styrenesulfonate) for Efficient Perovskite Solar Cells In article number 19000162, Qiuhong Cui, Yanbing Hou, and co-workers construct perovskite solar cells with discrete SnO SB 2 sb nanoparticle-modified layers by spin coating the SnO SB 2 sb dispersions on PEDOT:PSS. The discrete SnO SB 2 sb nanoparticle film lets holes pass and block electrons to diffuse toward PEDOT:PSS, which enhances the extraction efficiency, leading to an increase in power conversion efficiency. [Extracted from the article]

Although the performance of hybrid organic-inorganic perovskite solar cells (PSCs) is encouraging, the detailed working principles and mechanisms of PSCs remain to be further studied. In this work, an overshoot phenomenon of open-circuit voltage (Voc) was observed when the illumination light pulse was switched off. The evolution of the Voc overshoot was systematically investigated along with the intensity and the width of the light pulse, the background illumination, and pretreatment by different bias. Based on the experimental results, we could conclude that the Voc overshoot originated from carrier motion against carrier collection direction, which happened at the ionic-accumulation-induced band bending areas near the interfaces between the perovskite active layer and the two carrier transport layers. The investigation on the Voc overshoot can help us to better understand ionic migration, carrier accumulation, and recombination of PSCs under open-circuit conditions. [ABSTRACT FROM AUTHOR]

The improvement of the acetone-soaking treatment to the performance of polymer solar cells based on the P3HT/PCBM bulk heterojunction is reported. Undergoing acetone-soaking, the PCBM does not distribute uniformly in the vertical direction, a PCBM enrichment layer forms on the top of the active layer, which is beneficial to the collection of the carriers and blocking the inverting diffusion carriers. X-ray photoelectron spectroscopy (XPS) analysis reveals that the PCBM weight ratio on the top of the active layer increases by 20% after the acetone-soaking treatment. Due to the nonuniform distribution of PCBM, the short-circuit current density, the open-circuit voltage, and the fill factor are enhanced significantly. Finally, the power conversion efficiency of the acetone-soaking device increases by 31% compared with the control device. [ABSTRACT FROM AUTHOR]

Abstract: The effect of a thermal annealing treatment at various temperatures on the performance of bulk heterojunction photovoltaic cells based on poly[2-methoxy-5-(2′-ethyl-hexyloxy)-p-phenylene vinylene] (MEH-PPV) and buckminsterfullerene (C60) composites was investigated. With the increase in temperature, three stages were observed: from 60 to 120°C, the photovoltaic performance of the composite devices became better with the rising temperature; from 120 to 180°C, the photovoltaic performance decreased to a minimum; but, at about 200°C, a sharp rise occurred, followed by a gradual decline. The obvious red-shift of the photoluminescence (PL) spectra and the new PL peak and shoulder at about 620 and 660nm, respectively, indicated the formation of molecular aggregation and the lengthened and the ordered conjugated segments. It was suggested that the crystallization of C60 after thermal annealing at 200°C, which matched the nano-sized ordered domains of MEH-PPV led to a sharp enhancement in photovoltaic performance. [Copyright &y& Elsevier]

Abstract In this work, diethylammonium bromide (DABr) is used in planar perovskite solar cells to post-treat methylammonium iodide (MAPbI 3) films to fabricate high quality 2D/3D perovskite hybrid films. DABr treatment not only induces the small crystals secondary growth into large crystals, which lead to the formation of large-grain 3D perovskite films, but also forms a 2D DA 2 PbI 4- x Br x capping layer on the MAPbI 3 surface. The 2D DA 2 PbI 4- x Br x capping layer improves the moisture stability of the films. The larger grains and better crystallized 2D/3D perovskite films with fewer defects and interfacial contact between TiO x layer and active layer are beneficial to eliminate the light soaking effect and enhances the light stability. Transient PL spectra reveal that the 2D layer can act as an interface modification layer to promote the photogenerated carrier dissociation and hole extraction. By applying MAPbI 3 and 2D/3D perovskite film as light absorbers in PVSCs, we are able to enhance PCE from 14.37% to 18.30%. Graphical abstract Image 1 Highlights • DABr treatment can induce 2D/3D composite perovskite film with large grains about 1 μm. • 2D passivation layer on MAPbI 3 surface can enhance hole extraction of the device. • The preferable interfacial contact between TiO x and perovskite layer after DABr treatment eliminated light soaking effect. • DABr can boost the device efficiency from 14.37% to 18.30%. [ABSTRACT FROM AUTHOR]

In this work, we propose a facile microwave-assisted approach for annealing sol-gel derived ZnO films to serve as electron transport layers (ETLs) for inverted bulk heterojunction polymer solar cells. We have demonstrated an impressive enhancement in performance for devices based on a poly (3-hexylthiophene) (P3HT): (6,6)-phenyl-C 61 -butyric acid methyl ester (PC 61 BM) system employing the microwave-annealed ZnO (ZnO (MW)) ETLs in comparison to the cases using the conventional hotplate-annealed ZnO (ZnO (HP)) ones. The better electron transport in the device with the ZnO (MW) ETL is mainly ascribed to the preferable interfacial contact as evidenced by the morphology characteristics. Furthermore, the comprehensive analyses conducted from the light intensity dependent photocurrent and photovoltage measurements, the capacitance-voltage characteristics, and the alternating current impedance spectra suggest that the utilization of the ZnO (MW) ETLs can effectively suppress trap-assisted recombination as well as charge accumulation at the interface between P3HT: PC 61 BM layers and ZnO layers, which is responsible for the enhanced device performance. [ABSTRACT FROM AUTHOR]

The formation of a micro-nanostructured back electrode provides an efficient route for enhancing light absorption in polymer solar cells by light scattering of the bumpy electrode. In this study, we incorporated propylene glycol mono-methyl ether acetate (PGMEA) into the poly (3-hexylthiophene) (P3HT) and [6:6]-phenyl-C61-butyric acid (PC 61 BM) solution, and the PGMEA induced P3HT aggregations give rise to a bumpy surface of the active layer. The sequential deposition of the Al electrode onto the active layer creates a polymer solar cell with interpenetrated micro-nanostructured morphology of the active layer/electrode interface. The higher crystallinity of P3HT induced by active layer self-aggregation improves carrier mobility. The bumpy active layer/electrode interface can not only facilitate charge carriers transfer and collection in the device, but also enhance optical scattering and leads to enhanced light absorption of the active layer. The resulting device shows improved photocurrent, corresponding to power conversion efficiency improvement of 17.9% as compared to the planar device. This work indicates that the active layer self-aggregation is a simple, cost-effective and mold-free methodology to manufacture high performance polymer solar cells with the micro-nanostructured back electrode. [ABSTRACT FROM AUTHOR]

A series of solution processed organic solar cells (OSCs) were fabricated with a two-dimensional conjugated small molecule SMPV1 as electron donor and fullerene derivatives PC 71 BM or ICBA as electron acceptor. The champion power conversion efficiency (PCE) of OSCs arrives to 7.05% for the cells with PC 71 BM as electron acceptor. A relatively large open circuit voltage ( V OC ) of 1.15 V is obtained from cells using ICBA as electron acceptor with an acceptable PCE of 2.54%. The fill factor (FF) of OSCs is 72% or 61% for the cells with PC 71 BM or ICBA as electron acceptor, which is relatively high value for small molecule OSCs. The relatively low performance of OSCs with ICBA as electron acceptor indicates that ICBA cannot play positive role in photoelectric conversion processes, which is very similar to the phenomenon observed from the OSCs with high efficient narrow band gap polymers other than P3HT as electron donor, the underlying reason is still in debate. The SMPV1 has strong self-assemble ability to form an ordered two dimensional lamellar structure, which provides an effective platform to investigate the effect of electron acceptor chemical structure on the performance of OSCs. Experimental results exhibit that ICBA molecules may prefer to vertical cross-intercalation among side chains of SMPV1, PC 71 BM molecules may have better miscibility with SMPV1 in the active layer. The different donor/acceptor (D/A) intermolecular arrangement strongly influences photon harvesting, exciton dissociation and charge carrier transport, which may provide a new sight on performance improvement of OSCs by adjusting D/A intermolecular arrangements. [ABSTRACT FROM AUTHOR]

Solvent additive 1,8-diiodooctane (DIO) is not almighty for improving the performance of polymer solar cells (PSCs). In this paper, the effect of solvent additive DIO and ethanol treatment on the performance of polymer solar cells (PSCs) with poly{[4,9-dihydro-4,4,9,9-tetra(4-hexylbenzyl)-s-indaceno[1,2-b:5,6-b′]-dithiophene-2,7-diyl]-alt-[2,3-bis(3-(octyloxy)phenyl)-2,3-dihydro-quinoxaline-2,2′-diyl] (PIDTDTQx) and [6,6]-phenyl-C71-butyric acid methyl ester (PC 71 BM) as the active layer was investigated. The power conversion efficiency (PCE) was decreased from 4.57% to 1.96% by adding 4 vol% DIO solvent additive for the active layer processed with 1,2-dichlorobenzene (DCB) as solvent. The negative effect of DIO on PCE from 1.94% to 1.18% of PSCs processed with chlorobenzene (CB) as solvent was further demonstrated. The PCE values of PSCs with DIO additive can be effectively increased from 1.96% to 3.71% for DCB as solvent and from 1.18% to 1.89% for CB as solvent by ethanol treatment on the active layer. The crystalline and morphology of active layers play the key role in determining the performance of PSCs. [ABSTRACT FROM AUTHOR]

Abstract: The performance of polymer solar cells (PSCs), based on poly(3-hexylthiophene) (P3HT) and [6,6]phenyl-C71-butyric acid methyl ester (PC71BM), were improved by adding poly[(4,8-bis-(2-ethylhexyloxy)-benzo[1,2-b:4,5-b′](dithiophene)-2,6-diyl-alt-(4-(2-ethylhexanoyl)-thieno[3,4-b]thiophene)-2,6-diyl] (PBDTTT-C). The absorption region of the ternary blend films is extended into near infrared region (NIR). Power conversion efficiency (PCE) of the ternary blend PSCs is improved to 2.48% with 6% PBDTTT-C, which is 27% higher than the binary blend PSCs. The dominant mechanism for the PCE improvement could be attributed to the well balance between photon harvest and charge carrier transport by doping proper concentration PBDTTT-C. The energy transfer or charge carrier transfer directly between P3HT and PBDTTT-C was investigated, which are found to be positive for the performance improvement of ternary blend PSCs. [Copyright &y& Elsevier]

Abstract: Poly[2-methoxy-5-(3′,7′-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV) capped PbS quantum dots about 3–6nm in diameter were synthesized with a novel method. Unlike the synthesis of oleic acid capped PbS quantum dots, the reactions were carried out in solution at room temperature, with the presence of a capping ligand species, MDMO-PPV. The quantum dots were used to fabricate bulk heterojunction solar cells with an indium tin oxide (ITO)/polyethylenedioxythiophene/polystyrenesulphonate (PEDOT: PSS)/MDMO-PPV: PbS/Al structure. Current density–voltage characterization of the devices showed that after the addition of the MDMO-PPV capped PbS quantum dots to MDMO-PPV film, the performance was dramatically improved compared with pristine MDMO-PPV solar cells. [Copyright &y& Elsevier]

Abstract: The effect of post-thermal treatment under reverse bias on the performance of bulk heterojunction photovoltaic cells based on poly[2-methoxy-5-(20-ethylhexyloxy)-p-phenylene vinylene] (MEH-PPV) and fullerene (C60) composites is investigated. The experimental results show that treated devices deliver increased short-circuit current density (J sc) and conversion efficiency (η p) values. Especially, for the device annealed under the bias of −6V, the short-circuit current density (J sc) and the conversion efficiency (η p) are enhanced by a factor of 6 and 5.4, respectively. It is concluded that the enhancement of charge mobility induced by polymer chains modified orientation along the direction of electric field leads to a significant increase in the photovoltaic parameters. [Copyright &y& Elsevier]

The working mechanisms in the cadmium-free Cu–In–Zn–S(CIZS)-based quantum dot light-emitting didoes (QD-LEDs) were reported in previous reports, which were mai nly determined by the direct charge injection or the energy transfer. In this paper, we presented an improved device performance in solution-processed red-colored CIZS-based QD-LEDs by doping a small molecule 4,4′,4″-tris-(carbazol-9-yl)- triphenylamine (TCTA) into the emitting layer, and the best peak current efficiency of 3.22 cd A−1 and maximum luminance (L max) of 2679 cd m−2 could be achieved by optimizing the doping percentage of TCTA in the CIZS/ZnS nanocrystals (NCs). Such red-colored QD-LEDs exhibited a 210% increase in the current efficiency and no obvious change in the electroluminescence (EL) spectra as compared with the QD-LEDs without TCTA. The improvement of the device performance could be attributed to the synergistic effects of more balanced hole injection and the effective exciton energy transfer from TCTA to the NCs. The balanced hole injection could be verified by the fact that an increased current efficiency in the QD-LEDs by doping TCTA into an organic hole-transport layer. A class of symmetrical A-π-D-π-A type small molecules were designed theoretically by modification of terminal indenedione for applications in organic solar cells. Image 1 • All-solution-processed red-colored Cu–In–Zn–S-based QD-LEDs exhibited the best current efficiency of 3.22 cd A−1. • The device performance improvement was enabled by incorporation of TCTA into the emissive layer. • The incorporation of TCTA into the emissive layer resulted in reduced holes injection barrier and the effective exciton energy transfer from TCTA to the NCs. [ABSTRACT FROM AUTHOR]

Interfacial modification is an effective strategy to suppress the dark current in photodetectors for performance improvements. Here, solution-processed conjugated polymer electrolyte poly[(9,9-bis(3'-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)](PFN), widely used for interface engineering in organic and perovskite solar cells, is introduced to the photovoltaic photodetectors based on α-phase formamidinium lead iodide (α-FAPbI 3) perovskite at cathode interfaces. The PFN layer has both positive and negative impacts on the overall device performances. The steady-state device parameters including external quantum efficiency, photoresponsivity, and detectivity are enhanced because the dark current is effectively suppressed due to the hindered hole injection by the PFN layer. However, the incorporation of PFN leads to different transient photocurrent dynamics with a peak after turn-on and a long-lived tail after turn-off, increasing the fall time, although it has little impact on the rise time. The proposed mechanisms involve the trapping and detrapping effects of accumulated photogenerated electrons at the electron-transporting layer/PFN interface, which are proved by capacitance-voltage measurements and impedance spectroscopy analysis. Our results have important significance for understanding the different effects and mechanisms of conjugated polymer electrolytes for interfacial engineering in photodetectors and solar cells and selecting suitable interfacial materials for electrode modification in photodetectors. Interfacial modification by an ultrathin conjugated polymer electrolyte PFN layer in the α-FAPbI 3 photodetectors efficiently suppresses the dark current due to the hindered hole injection, and results in obvious steady-state performance improvements, showing an on/off current ratio of 2.72 × 104 at −0.5 V. Nevertheless, it also leads to different transient photocurrent dynamics with a transient peak after turn-on and a long-lived tail after turn-off by the trapping and detrapping effects of accumulated photogenerated electrons at the PC 61 BM/PFN interface. Image 1 • Introducing a cathode modification layer of PFN to decrease the dark current in p-i-n photodetectors. • Showing the trapping and detrapping effects of accumulated photogenerated electrons at the PCBM/PFN interface. • Inserting PFN results in unusual transient photocurrent dynamics in p-i-n α-FAPbI3 photodetectors. [ABSTRACT FROM AUTHOR]

Although tin-based perovskite has been considered as a kind of potential environmentally-friendly photovoltaic materials, the tin-based perovskite solar cells are limited due to their poor stability and low conversion efficiency mainly tracing to the oxidation from Sn2+ to Sn4+ state in tin-based perovskite films. Herein, a facile reductive approach is developed to suppress the oxidation, in which tiny amount of hydrazine monohydrobromide is doped into FASnI 3 -based perovskite precursor solution as a reducing agent. Our results demonstrate that the addition of hydrazine monohydrobromide could reduce the defects and trap states in perovskite by inhibiting formation of tetravalent tin, and increase the open circuit voltage by widening the bandgap of perovskite. As a consequence, the best optimized perovskite solar cell achieves an excellent power conversion efficiency of 7.81%, which represented a 39.5% improvement compared to the best reference device. The optimized devices display stabilized power output near the maximum power point and negligible hysteresis effect. A tiny amount of hydrazine monohydrobromide doping into FASnI 3 precursor solution can inhibit formation of tetravalent tin and increase the open circuit voltage of devices. Consequently, the best optimized perovskite solar cell achieves an excellent power conversion efficiency of 7.81%, which represented a 39.5% improvement compared to the best reference device. Image 1 • The addition of hydrazine monohydrobromide could reduce the defects and trap states in perovskite by inhibiting formation of tetravalent tin. • The addition of hydrazine monohydrobromide could increase the open circuit voltage by widening the bandgap of perovskite. • Perovskite is a pure tin-based material without lead. • The optimized device achieves an excellent power conversion efficiency of 7.81%, which represented a 39.5% improvement. [ABSTRACT FROM AUTHOR]