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Reduced Non-radiative Recombination Energy Loss Enabled Efficient Polymer Solar Cells via Tuning Alkyl Chain Positions on Pendent Benzene Units of Polymers
摘要： Non-radiative recombination energy loss (ΔE3) plays a key role in enhancing device efficiencies for polymer solar cells (PSCs). Up to now, there is no clear resolution for reducing ΔE3 via molecular design. Herein, we report two conjugated polymers, PBDB-P-p and PBDB-P-m, which are integrated from benzo[1,2-b:4,5-b′]dithiophene (BDT) with alkylthio chain substituted at para- or meta- position on pendent benzene and benzo[1,2-c:4,5-c′]dithiophene-4,8-dione (BDD). Two polymers have different temperature-dependent aggregation properties, but similar molecular energy levels. When BO-4Cl was used as acceptor to fabricate PSCs, the device of PBDB-P-p:BO-4Cl displayed a maximal power conversion efficiency (PCE) of 13.83%, while the best device of PBDB-P-m:BO-4Cl exhibited a higher PCE of 14.12%. The close JSCs and FFs in both PSCs are attributed to their formation of effective nanoscale phase-separation as confirmed by atomic force microscopy (AFM) measurements. We find that the PBDB-P-m-based device has one order of magnitude higher of electroluminescence quantum efficiency (EQEEL) than that in PBDB-P-p-based one, which could arise from the relatively weak aggregation in PBDB-P-m-based film. Thus, the PBDB-P-m-based device has a remarkably enhanced VOC of 0.86 V in contrast to 0.80 V in PBDB-P-p-based device. This study offers a feasible structural optimization way on the alkylthio side chain substitute position on the conjugated polymer to enhance VOC by reducing non-radiative recombination energy loss in resulting PSCs.
关键词： polymer solar cells,open-circuit voltage,non-radiative recombination energy loss,polymer donor,alkylthio substituted position
更新于2025-09-23 15:21:01
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Tailoring Perovskite Adjacent Interfaces by Conjugated Polyelectrolyte for Stable and Efficient Solar Cells
摘要： Interface engineering is an effective means to enhance the performance of thin film devices, such as perovskite solar cells (PSCs). Here, a conjugated polyelectrolyte, poly[(9,9-bis(3'-((N,N-dimethyl)-N-ethyl-ammonium)-propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)]di-iodide (PFN-I), is employed at the interfaces between the hole transport layer (HTL)/perovskite and perovskite/electron transport layer (ETL) simultaneously, to enhance the device power conversion efficiency (PCE) and stability. The fabricated PSCs with an inverted planar heterojunction structure show improved open-circuit voltage (Voc), short-circuit current density (Jsc) and fill factor (FF), resulting in PCEs up to 20.56%. The devices maintain over 80% of their initial PCEs after 800 hours of exposure to a relative humidity 35-55 % at room temperature. All of these improvements are attributed to the functional PFN-I layers as they provide favorable interface contact and defect reduction.
关键词： perovskite solar cells,non-radiative recombination,conjugated polyelectrolytes,interface engineering
更新于2025-09-23 15:19:57
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Modeling of Injection-dependent Non-radiative Recombination via Point and Extended Defects in mc-Si
摘要： Non-radiative (NR) carrier recombination limits the efficiency of photovoltaic energy conversion. Minority carrier lifetimes in Si exhibit a variety of dependences on optical injection levels, depending on the types of defects present. To date, models of non-radiative recombination in silicon were proposed for point defects (e.g., Fe interstitials) and extended defects (e.g., dislocations). Direct measurement of local carrier concentration near recombination centers is technically difficult, therefore, computational modeling may be helpful to understand various carrier recombination pathways in materials such as mc-Si. In this paper, modeling is used to compare intensity-dependent NR recombination lifetimes in Si. The usefulness of the model goes beyond mc-Si photovoltaics.
关键词： interstitials,numerical modeling,non-radiative recombination,silicon,Dislocations
更新于2025-09-23 15:19:57
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Amphoteric imidazole doping induced large-grained perovskite with reduced defect density for high performance inverted solar cells
摘要： Intrinsic defect density in polycrystalline halide perovskite films are required to be low enough to suppress charge recombination loss for improvement in performance of perovskite solar cells (PeSCs). In this paper, we propose the use of amphoteric imidazole to achieve high crystalline quality of CH3NH3PbI3 perovskite absorption layer. The imidazole additive plays a synergistic role in controlling the perovskite crystal growth for large grain size and passivating the uncoordinated ions (e.g., Pb2+) defects, resulting in improved carrier transport/lifetime and suppressed non-radiative recombination. The champion power conversion efficiency (PCE) of PeSCs with imidazole is improved to 16.88%, from the control device with a PCE value of 14.65%. Besides, the stability of imidazole modified perovskite films is further improved by limiting ion immigration at grain boundaries against moisture and heat stresses. The findings pave an avenue for synergistically modulating crystallization and healing defect in perovskite to achieve efficient and stable solar cells.
关键词： Defect passivation,CH3NH3PbI3,Grain boundary,Inverted solar cell,Non-radiative recombination
更新于2025-09-23 15:19:57
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Efficient Perovskite Solar Cells by Reducing Interfacea??Mediated Recombination: a Bulky Amine Approach
摘要： The presence of non-radiative recombination at the perovskite surface/interface limits the overall efficiency of perovskite solar cells (PSCs). Surface passivation has been demonstrated as an efficient strategy to suppress such recombination in Si cells. Here, 1-naphthylmethylamine iodide (NMAI) is judiciously selected to passivate the surface of the perovskite film. In contrast to the popular phenylethylammonium iodide, NMAI post-treatment primarily leaves NMAI salt on the surface of the perovskite film. The formed NMAI layer not only efficiently decreases the defect-assisted recombination for chemical passivation, but also retards the charge accumulation of energy level mis-alignment for vacuum level bending and prevents minority carrier recombination due to the charge-blocking effect. Consequently, planar PSCs with high efficiency of 21.04% and improved long-term stability (98.9% of the initial efficiency after 3240 h) are obtained. Moreover, open-circuit voltage as high as 1.20 V is achieved at the absorption threshold of 1.61 eV, which is among the highest reported values in planar PSCs. This work provides new insights into the passivation mechanisms of organic ammonium salts and suggests future guidelines for developing improved passivation layers.
关键词： perovskite solar cells,energy level alignment,1-naphthylmethylamine iodide,non-radiative recombination,chemical passivation
更新于2025-09-23 15:19:57
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Ba-induced phase segregation and band gap reduction in mixed-halide inorganic perovskite solar cells
摘要： All-inorganic metal halide perovskites are showing promising development towards efficient long-term stable materials and solar cells. Element doping, especially on the lead site, has been proved to be a useful strategy to obtain the desired film quality and material phase for high efficient and stable inorganic perovskite solar cells. Here we demonstrate a function by adding barium in CsPbI2Br. We find that barium is not incorporated into the perovskite lattice but induces phase segregation, resulting in a change in the iodide/bromide ratio compared with the precursor stoichiometry and consequently a reduction in the band gap energy of the perovskite phase. The device with 20 mol% barium shows a high power conversion efficiency of 14.0% and a great suppression of non-radiative recombination within the inorganic perovskite, yielding a high open-circuit voltage of 1.33 V and an external quantum efficiency of electroluminescence of 10?4.
关键词： inorganic perovskite solar cells,barium doping,non-radiative recombination,band gap reduction,phase segregation
更新于2025-09-19 17:13:59
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Analysis of dominant non-radiative recombination mechanisms in InGaN green LEDs grown on silicon substrates
摘要： Relationship between the external quantum efficiency (EQE) curves and the dominant non-radiative recombination mechanisms of InGaN green LEDs grown on silicon substrates were investigated. Through the analysis of the ABC+(cid:1)(cid:2)(cid:3)(cid:4) model, the significant drop in EQE at low current levels is due to an increasingly defect-related Shockley-Read-Hall (SRH) recombination. Under extremely low current densities, the defect traps can even become the dominant channel for the leakage current through the tunneling process, thereby reducing the efficiency of carrier injection into the active region. These observations were further supported by the carrier lifetime measurement. However, this fails to explain the droop in EQE at high current densities, especially when SRH recombination has been saturated. Our results show that carrier leakage has becomes dominant at high current density when Auger recombination has been less impossible. Reduced carrier leakage may lead to increased carrier injection efficiency, which in turn alleviates EQE droop.
关键词： silicon substrates,InGaN,non-radiative recombination,green LEDs,external quantum efficiency,carrier leakage
更新于2025-09-19 17:13:59
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Investigation on voltage loss in organic triplet photovoltaic devices based on Ir complexes
摘要： Voltage losses in singlet material-based organic photovoltaic devices (OPVs) have been intensively studied, whereas, only a few investigations on triplet material-based OPVs (T-OPVs) are reported. To investigate the voltage loss in T-OPVs, two homoleptic iridium(III) complexes based on extended p-conjugated benzo[g]phthalazine ligands, Ir(Ftbpa)3 and Ir(FOtbpa)3, are synthesized as sole electron donors. T-OPVs are fabricated by mixing two donors with phenyl-C71-butyric acid methyl ester (PC71BM) as an electron acceptor. Insertion of oxygen-bridges as flexible inert d-spacers in Ir(FOtbpa)3 has slightly elevated both the lowest unoccupied molecular orbital and the highest occupied molecular orbital levels compared to those of Ir(Ftbpa)3, which results in a lower charge transfer (CT) state energy (ECT) for Ir(FOtbpa)3-based devices. However, a higher Voc (0.88 V) is observed for Ir(FOtbpa)3-based devices than those of Ir(Ftbpa)3 (0.80 V). To understand the above result, the morphologies of the two blend films are studied, which excludes the influence of morphology. Furthermore, radiative and non-radiative recombination in two devices is quantitatively investigated, which suggests that a higher Voc can be attributed to reduced radiative and non-radiative recombination loss for the Ir(FOtbpa)3-based devices.
关键词： charge transfer state energy,organic photovoltaic devices,triplet material-based OPVs,radiative and non-radiative recombination,iridium(III) complexes,voltage loss
更新于2025-09-12 10:27:22
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Voltage dependent photoluminescence and how it correlates to the fill factor and open-circuit voltage in perovskite solar cells
摘要： Optimizing the photoluminescence (PL) yield of a solar cell has long been recognized as a key principle to maximize the power conversion efficiency. While PL measurements are routinely applied to perovskite films and solar cells under open-circuit conditions (VOC), it remains unclear how the emission depends on the applied voltage. Here, we performed PL(V) measurements on perovskite cells with different hole transport layer thicknesses and doping concentrations resulting in remarkably different fill factors (FFs). The results reveal that PL(V) mirrors the current-voltage (JV) characteristics in the power-generating regime, which highlights an interesting correlation between radiative and non-radiative recombination losses. In particular, high FF devices show a rapid quenching of PL(V) from open-circuit to the maximum power point. We conclude that while the PL has to be maximized at VOC, at lower biases <VOC, the PL must be rapidly quenched as charges need to be extracted prior to recombination.
关键词： perovskite solar cells,radiative recombination,photoluminescence,open-circuit voltage,fill factor,non-radiative recombination
更新于2025-09-11 14:15:04
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Minimizing non-radiative recombination losses in perovskite solar cells
摘要： Photovoltaic solar cells based on metal-halide perovskites have gained considerable attention over the past decade because of their potentially low production cost, earth-abundant raw materials, ease of fabrication and ever-increasing power-conversion efficiencies of up to 25.2%. This type of solar cells offers the promise of generating electricity at a more competitive unit price than traditional fossil fuels by 2035. Nevertheless, the best research-cell efficiencies are still below the theoretical limit defined by the Shockley–Queisser theory, owing to the presence of non-radiative recombination losses. In this Review, we analyse the predominant pathways that contribute to non-radiative recombination losses in perovskite solar cells and evaluate their impact on device performance. We then discuss how non-radiative recombination losses can be estimated through reliable characterization techniques and highlight some notable advances in mitigating these losses, which hint at pathways towards defect-free perovskite solar cells. Finally, we outline directions for future work that will push the efficiency of perovskite solar cells towards the radiative limit.
关键词： defect passivation,photovoltaic,perovskite solar cells,Shockley–Queisser theory,non-radiative recombination losses
更新于2025-09-11 14:15:04