Efficiency Enhancement with the Ferroelectric Coupling Effect Using P(VDF-TrFE) in CH3NH3PbI3 Solar Cells.

A novel ferroelectric coupling photovoltaic effect is reported to enhance the open-circuit voltage (V OC) and the efficiency of CH3NH3PbI3 perovskite solar cells. A theoretical analysis demonstrates that this ferroelectric coupling effect can effectively promote charge extraction as well as suppress combination loss for an increased minority carrier lifetime. In this study, a ferroelectric polymer P(VDF-TrFE) is introduced to the absorber layer in solar cells with a proper cocrystalline process. Piezoresponse force microscopy (PFM) is used to confirm that the P(VDF-TrFE):CH3NH3PbI3 mixed thin films possess ferroelectricity, while the pure CH3NH3PbI3 films have no obvious PFM response. Additionally, with the applied external bias voltages on the ferroelectric films, the devices begin to show tunable photovoltaic performance, as expected for the polarization in the poling process. Furthermore, it is shown that through the ferroelectric coupled effect, the efficiency of the CH3NH3PbI3-based perovskite photovoltaic devices is enhanced by about 30%, from 13.4% to 17.3%. And the open-circuit voltages (V OC) reach 1.17 from 1.08 V, which is reported to be among the highest V OCs for CH3NH3PbI3-based devices. It should be noted in particular that the thickness of the layer is less than 160 nm, which can be regarded as semi-transparent.

Erratum: Superior Stability and Efficiency Over 20% Perovskite Solar Cells Achieved by a Novel Molecularly Engineered Rutin-AgNPs/Thiophene Copolymer.

[This corrects the article DOI: 10.1002/advs.201800568.].

Moisture-tolerant supermolecule for the stability enhancement of organic-inorganic perovskite solar cells in ambient air.

Instability of the perovskite materials, especially in high humidity, is one of the major limitations that hinders the development of perovskite devices. Herein, to eliminate the degradation of perovskite solar cells in humid air, a water-resistant perovskite absorption layer is proposed by introducing a macrocycle-type cyclodextrin material (ß-CD) into the films. The ß-CD was proved to be capable of facilitating the crystallization of grains and enhancing the stability of the perovskite by forming supramolecular interactions with organic cations through the hydrogen bonding in the perovskite films. Consequently, the average efficiency of the PSCs remarkably increased from 16.19% to 19.98%. The champion solar cell even delivered an efficiency of 20.09%. The PSCs with ß-CD exhibited superior long-term stability in ambient air without encapsulation, which retained 90% of the initial efficiency after continuous AM 1.5 illumination in ambient air with 80% humidity for 300 h.

Computational Study of Ternary Devices: Stable, Low-Cost, and Efficient Planar Perovskite Solar Cells.

Although perovskite solar cells with power conversion efficiencies (PCEs) more than 22% have been realized with expensive organic charge-transporting materials, their stability and high cost remain to be addressed. In this work, the perovskite configuration of MAPbX (MA = CH3NH3, X = I3, Br3, or I2Br) integrated with stable and low-cost Cu:NiO x hole-transporting material, ZnO electron-transporting material, and Al counter electrode was modeled as a planar PSC and studied theoretically. A solar cell simulation program (wxAMPS), which served as an update of the popular solar cell simulation tool (AMPS: Analysis of Microelectronic and Photonic Structures), was used. The study yielded a detailed understanding of the role of each component in the solar cell and its effect on the photovoltaic parameters as a whole. The bandgap of active materials and operating temperature of the modeled solar cell were shown to influence the solar cell performance in a significant way. Further, the simulation results reveal a strong dependence of photovoltaic parameters on the thickness and defect density of the light-absorbing layers. Under moderate simulation conditions, the MAPbBr3 and MAPbI2Br cells recorded the highest PCEs of 20.58 and 19.08%, respectively, while MAPbI3 cell gave a value of 16.14%.

Superior Stability and Efficiency Over 20% Perovskite Solar Cells Achieved by a Novel Molecularly Engineered Rutin-AgNPs/Thiophene Copolymer.

Perovskite solar cells (PSCs) with efficiencies greater than 20% have been realized mostly with expensive spiro-MeOTAD hole-transporting material. PSCs are demonstrated that achieve stabilized efficiencies exceeding 20% with straightforward low-cost molecularly engineered copolymer poly(1-(4-hexylphenyl)-2,5-di(thiophen-2-yl)-1H-pyrrole) (PHPT-py) based on Rutin-silver nanoparticles (AgNPs) as the hole extraction layer. The Rutin-AgNPs additive enables the creation of compact, highly conformal PHPT-py layers that facilitate rapid carrier extraction and collection. The spiro-MeOTAD-based PSCs show comparable efficiency, although their operational stability is poor. This instability originated from potential-induced degradation of the spiro-MeOTAD/Au contact. The addition of conductive Rutin-AgNPs into PHPT-py layer allows PSCs to retain >97% of their initial efficiency up to 60 d without encapsulation under relative humidity. The PHPT-py/ Rutin-AgNPs-based devices surpass the stability of spiro-MeOTAD-based PSCs and potentially reduce the fabrication cost of PSCs.

Ion-Migration Inhibition by the Cation-π Interaction in Perovskite Materials for Efficient and Stable Perovskite Solar Cells.

Migration of ions can lead to photoinduced phase separation, degradation, and current-voltage hysteresis in perovskite solar cells (PSCs), and has become a serious drawback for the organic-inorganic hybrid perovskite materials (OIPs). Here, the inhibition of ion migration is realized by the supramolecular cation-π interaction between aromatic rubrene and organic cations in OIPs. The energy of the cation-π interaction between rubrene and perovskite is found to be as strong as 1.5 eV, which is enough to immobilize the organic cations in OIPs; this will thus will lead to the obvious reduction of defects in perovskite films and outstanding stability in devices. By employing the cation-immobilized OIPs to fabricate perovskite solar cells (PSCs), a champion efficiency of 20.86% and certified efficiency of 20.80% with negligible hysteresis are acquired. In addition, the long-term stability of cation-immobilized PSCs is improved definitely (98% of the initial efficiency after 720 h operation), which is assigned to the inhibition of ionic diffusions in cation-immobilized OIPs. This cation-π interaction between cations and the supramolecular π system enhances the stability and the performance of PSCs efficiently and would be a potential universal approach to get the more stable perovskite devices.