Tailoring tin oxide layersMesoporous titanium dioxide is commonly used as the electron transport layer in perovskite solar cells, but electron transport layers based on tin(IV) oxide quantum dots ...could be more efficient, with a better-aligned conduction band and a higher carrier mobility. Kim et al. show that such quantum dots could conformally coat a textured fluorine-doped tin oxide electrode when stabilized with polyacrylic acid. Improved light trapping and reduced nonradiative recombination resulted in a certified power conversion efficiency of 25.4% and high operational stability. In larger-area minimodules, active areas as high as 64 square centimeters maintained certified power conversion efficiencies of more than 20%. —PDS
Phenyl-C61-butyric acid methyl ester (PCBM) can be used as a passivation material in perovskite solar cells (PeSCs) in order to reduce the trap site of the perovskite. Here, we show that a thick PCBM ...layer can form a smoother surface on the SnO2 substrate, improving the grain size and reducing the microstrain of the perovskite. High-temperature annealing treatment of PCBM layer not only increases its solvent resistance to perovskite precursor or antisolvent, but also enhances its molecular alignment, resulting in improved conductivity as an electron transport layer. High-temperature annealed PCBM (HT-PCBM) effectively minimizes trap-assisted nonradiative recombination by reducing trap density in perovskite and improving the electrical properties at the interface between SnO2 and perovskite layers. This HT-PCBM process significantly enhances the performance of the PeSCs, including the open-circuit voltage (V OC) from 0.39 to 0.77 V, fill factor from 52% to 65%, and power conversion efficiency (PCE) from 6.03% to 15.50%, representing substantial improvements compared to devices without PCBM. This PCE is the highest efficiency among conventional (n-i-p) Sn–Pb PeSCs reported to date. Moreover, passivating the trap sites of SnO2 and separating the interface between the Sn-containing perovskite and the substrate effectively have improved the stability of the Sn–Pb perovskite in the n-i-p structure. The optimized best device with HT-PCBM has maintained an efficiency of over 90% for more than 300 h at 85 °C and 5000 h at room temperature in a glovebox atmosphere.
Vacuum deposition of perovskites is a promising method for scale-up fabrication and uniform film growth. However, improvements in the photovoltaic performance of perovskites are limited by the ...fabrication of perovskite films, which are not optimized for high device efficiency in the vacuum evaporation process. Herein, we fabricate CsPbI2Br perovskite with high crystallinity and larger grain size by controlling the deposition sequence between PbI2 and CsBr. The nucleation barrier for perovskite formation is significantly lowered by first evaporating CsBr and then PbI2 (CsBr–PbI2), followed by the sequential evaporation of multiple layers. The results show that the reduced Gibbs free energy of CsBr–PbI2, compared with that of PbI2–CsBr, accelerates perovskite formation, resulting in larger grain size and reduced defect density. Furthermore, surface-modified homojunction perovskites are fabricated to efficiently extract charge carriers and enhance the efficiency of perovskite solar cells (PeSCs) by modulating the final PbI2 thickness before thermal annealing. Using these strategies, the best PeSC exhibits a power conversion efficiency of 13.41% for a small area (0.135 cm2), the highest value among sequential thermal deposition inorganic PeSCs, and 11.10% for a large area PeSC (1 cm2). This study presents an effective way to understand the crystal growth of thermally deposited perovskites and improve their performance in optoelectronic devices.
Phenyl-C
-butyric acid methyl ester (PCBM) can be used as a passivation material in perovskite solar cells (PeSCs) in order to reduce the trap site of the perovskite. Here, we show that a thick PCBM ...layer can form a smoother surface on the SnO
substrate, improving the grain size and reducing the microstrain of the perovskite. High-temperature annealing treatment of PCBM layer not only increases its solvent resistance to perovskite precursor or antisolvent, but also enhances its molecular alignment, resulting in improved conductivity as an electron transport layer. High-temperature annealed PCBM (HT-PCBM) effectively minimizes trap-assisted nonradiative recombination by reducing trap density in perovskite and improving the electrical properties at the interface between SnO
and perovskite layers. This HT-PCBM process significantly enhances the performance of the PeSCs, including the open-circuit voltage (
) from 0.39 to 0.77 V, fill factor from 52% to 65%, and power conversion efficiency (PCE) from 6.03% to 15.50%, representing substantial improvements compared to devices without PCBM. This PCE is the highest efficiency among conventional (n-i-p) Sn-Pb PeSCs reported to date. Moreover, passivating the trap sites of SnO
and separating the interface between the Sn-containing perovskite and the substrate effectively have improved the stability of the Sn-Pb perovskite in the n-i-p structure. The optimized best device with HT-PCBM has maintained an efficiency of over 90% for more than 300 h at 85 °C and 5000 h at room temperature in a glovebox atmosphere.
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•Highly efficient hole transporting layer-free organic solar cells.•Phosphotungstic Acid as a hole transport layer and a solid additive.•Simplified fabrication technique for cell to ...module development.•Organic solar cells with reduced trap-states and recombination losses.•Development of efficient, scalable and sustainable organic solar cells.
Interfacial layers play a crucial role in enhancing the performances and stabilities of organic solar cells (OSCs). Despite achieving high efficiencies from OSCs, the challenges associated with large-area manufacturing and the need for nanoscale uniformity during coating have hindered the large-scale production of these devices. To address these issues, we propose the concept of hole transport layer (HTL)-free OSCs to simplify the fabrication processes and improve the efficiency of production. In this study, we explore the potential of phosphotungstic acid (PTA), a Keggin polyoxometalate, both as a promising HTL and as an additive in HTL-free OSCs to enhance device performances and scalabilities in cell-to-module OSCs. Remarkably, incorporating PTA as an annealing-free HTL and as an additive in the photoactive layer (PM6:Y6:PC71BM) significantly increases power conversion efficiency (PCE) up to 17.28 % and 16.33 %, respectively, with respect to that of the reference device with PEDOT:PSS (15.88 %). We successfully fabricate a large-area OSC module, exhibiting an impressive PCE of 15.18 % and an active area of 54 cm2, achieving approximately 85 % of the effectiveness of small-area OSCs. The improved performance is attributed to the enhanced transmittance, excellent carrier-dynamic capacity, suppressed carrier recombination, and reduced trap-states in the ternary bulk-heterojunction OSCs. This study demonstrates the promising versatility of PTA for application in OSCs, offering potential enhancements in device performance and scalability for future applications.
The cathode interlayer (CIL) is vital for enhancing the performance of inverted (p-i-n) perovskite solar cells (PSCs) by preventing charge recombination and ion diffusion, thereby achieving superior ...efficiency. Herein, we introduce cost-effective perylene-diimide (PDI)-based CILs—PDIN-S, PDIN, and PDIN-L—with varying spacer lengths. Among them, PDIN-S exhibits exceptional attributes in thermal evaporation processability, optical absorbance, and charge transfer capabilities. Molecular orientations of PDIN-S are studied through two deposition techniques: vacuum thermal evaporation (VE) and spin-coating (SC). The face-on orientation observed in PDIN-S (VE) confers significant advantages, including improved π–π stacking, efficient charge carrier transfer, reduced interfacial resistance, and inhibited ion diffusion. Furthermore, PDIN-S (VE) also lowers the energy barrier towards cathode, boosting PSC efficiency to 23.82%. Moreover, it enhances both thermal and light stability, maintaining over 90% initial efficiency for 2036 h at 85 °C and sustaining 80% efficiency for 1848 h under continuous illumination. Our application of a straightforward VE method enables the manipulation of molecular orientation, resulting in a concurrent enhancement of efficiency and stability. These findings underscore the potential of PDIN-S as a promising component for highly efficient and stable PSCs.
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•PDIN derivatives were synthesized through the modulation of alkyl spacer length.•PDIN-S film via vacuum thermal evaporation (PDIN-S (VE)) exhibited face-on orientation.•Employing PDIN-S (VE) as the cathode interlayer (CIL) enhanced the power conversion efficiency from 21.18% to 23.82%.•PDIN-S (VE) resulted in decreased ion diffusion, enhancing thermal (T90≈2036 h) and light stability (T80≈1848 h).
In addition to the phase-separated morphology of donor and acceptor, the internal field created by work-function difference between cathode and anode can also influence the exciton dissociation ...probability. In this study, we have demonstrated enhanced photovoltaic performance by increasing exciton dissociation efficiency. To improve both work-function modification effect and charge transport properties, we have incorporated novel carbon quantum dots (CQD) having NH2 ligands into the polyethyleneimine (PEI) work-function modifying layer as a dopant. A study of net photocurrent density as a function of effective voltage showed that devices with a CQD-doped PEI layer had a much higher charge separation probability compared to devices with a pristine PEI layer. A Kelvin-probe force microscopy study demonstrated that a CQD-doped PEI layer induced lower work-function of ITO than that of ITO with a pristine PEI, which induced a stronger internal field. This strengthened internal field induced better exciton dissociation efficiency, thereby improving solar cell performance.
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•Carbon quantum dots (CQDs) were synthesized, and incorporated into the PEI interfacial layer.•Significantly improved exciton dissociation efficiency was achieved with CQD having NH2 ligands.•CQD doped PEI layer induced stronger internal field, and led to improvement of charge separation probability.
In early studies on organic solar cells with high conductivity PEDOT:PSS, the contact between ITO and PEDOT:PSS was considered ohmic. However, because low-conductivity PEDOT:PSS (such as AI4083) is ...mainly utilized in contemporary solar cells, the contact between ITO and PEDOT:PSS is not ohmic anymore. Despite the high possibility that there are serious interface problems, little attention has been paid to the interface between PEDOT:PSS and ITO. Most of the previous studies of interfaces in organic solar cells have focused on the interface between the active and charge transport layers. In this work, we have employed a conjugated polyelectrolyte that uses potassium poly9,9-bis(3′-sulfonatopropyl)fluorene
-alt-
(9-(2,7-diethylheptyl)-carboazole) (WPFSCz-) between ITO and low-conductivity PEDOT:PSS to overcome complicated organic-inorganic interfacial problems. The insertion of the WPFSCz- layer provides substantial advantages in the operation of polymer solar cells. First, the inserted WPFSCz- layer modifies the work-function of ITO, thereby forming an effective cascading energy alignment, which is favorable for good hole transport. Second, the introduction of the WPFSCz- layer eliminates interfacial trap sites. The reduction in traps reduces recombination losses at the interface, resulting in an improvement in the fill factor. These effects result in a significant increase in the efficiency of non-fullerene solar cells based on PM6 and Y6, from 15.86 to 17.34%. In addition, we have found that the problem of the interface in contact with ITO occurs not only in PEDOT:PSS, but also in oxide-based charge transport layers. We have confirmed that the insertion of the WPFSCz- layer between ITO and an MoO
3
(or ZnO) charge transport layer shows the same positive results.
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-).
Improvements to perovskite solar cells (PSCs) have focused on increasing their power conversion efficiency (PCE) and operational stability and maintaining high performance upon scale-up to module ...sizes. We report that replacing the commonly used mesoporous-titanium dioxide electron transport layer (ETL) with a thin layer of polyacrylic acid-stabilized tin(IV) oxide quantum dots (paa-QD-SnO
) on the compact-titanium dioxide enhanced light capture and largely suppressed nonradiative recombination at the ETL-perovskite interface. The use of paa-QD-SnO
as electron-selective contact enabled PSCs (0.08 square centimeters) with a PCE of 25.7% (certified 25.4%) and high operational stability and facilitated the scale-up of the PSCs to larger areas. PCEs of 23.3, 21.7, and 20.6% were achieved for PSCs with active areas of 1, 20, and 64 square centimeters, respectively.
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