Perovskite thin-film solar cell: excitation in photovoltaic science

Interface engineering and defect passivation for enhanced hole extraction, ion migration, and optimal charge dynamics in both lead-based and lead-free perovskite solar cells

The study elucidates the potential benefits of incorporating a BiI3 interfacial layer into perovskite solar cells (PSCs). Using MAPbI3 and MAGeI3 as active layers, complemented by the robust TiO2 and Spiro-OMeTAD as the charge-transport-layers, we employed the SCAPS-1D simulation tool for our investigations. Remarkably, the introduction of the BiI3 layer at the perovskite-HTL interface significantly enhanced hole extraction and effectively passivated defects. This approach minimized charge recombination and ion migration towards opposite electrodes, thus elevating device performance relative to conventional configurations. The efficiency witnessed a rise from 19.28 to 20.30% for MAPbI3 and from 11.90 to 15.57% for MAGeI3. Additionally, MAGeI3 based PSCs saw an improved fill-factor from 50.36 to 62.85%, and a better Jsc from 13.22 to 14.2 mA/cm2, signifying reduced recombination and improved charge extraction. The FF for MAPbI3 based PSCs saw a minor decline, while the Voc slightly ascended from 1.24 to 1.25 V and Jsc from 20.01 to 21.6 mA/cm2. A thorough evaluation of layer thickness, doping, and temperature further highlighted the critical role of the BiI3 layer for both perovskite variants. Our examination of bandgap alignments in devices with the BiI3 interfacial layer also offers valuable understanding into the mechanisms fueling the observed improvements.

Design and optimization of non-toxic and highly efficient tin-based organic perovskite solar cells by device simulation

An organic, lead-free, n-i-p planar perovskite solar cell (PSC) based on CH3NH3SnI3 was demonstrated in this work using a solar cell capacitance simulator (SCAPS). A material cell design of FTO/ZnO/CH3NH3SnI3/Cu2O/Au has been investigated for this study. A detailed analysis has been performed on the role of thickness, electron affinity, doping concentration of the perovskite layer, ETL, HTL, defect density of perovskite layer and temperature on PSC performance. For optimum conditions, the energy conversion efficiency is around 26.55%, accompanied by fill factor = 85.58%, open circuit voltage = 1.03 V, short circuit current density = 30.14 mA/cm2, and quantum efficiency of 80%-90%. This model shows the prospect of CH3NH3SnI3 as a perovskite material to produce toxic-free environment-friendly solar cells with high efficiency.

Strain induced electronic structure variation in methyl-ammonium lead iodide perovskite

Methyl-ammonium lead iodide perovskite (CH₃NH₃PbI₃) has drawn great attention due to its excellent photovoltaic properties. Because of its loosely compacted structure, the structural, electronic and optical properties of CH₃NH₃PbI₃ are sensitive to external modulations. Strain effects on CH₃NH₃PbI₃ are fully investigated by the first principles calculations. The results indicate that the inorganic framework deforms under compression or stretch and the embedded organic CH₃NH₃+ molecules rotate correspondingly. A band gap oscillation and a new structural phase in response to the external strain were observed for the first time. These phenomena are explained with the nonlinear structural deformation and phase transition under the external strains. The semi-quantitative relationship between the band gap variation and geometry change under the external strain is obtained. We found that the shift of valence band maximum under the external strain is mostly determined by the most stretched or compressed Pb-I bond of CH₃NH₃PbI₃, and the shift of the conduction band minimum under the external strain is likely to be determined by the largest Pb-I-Pb bond angle in the system. These results are important for understanding of strain effects on semiconductors and guiding the experiments to improve the performance of the perovskite solar cells.

Microscopic Charge Transport and Recombination Processes behind the Photoelectric Hysteresis in Perovskite Solar Cells

The microscopic charge transport and recombination processes behind the widely concerned photoelectric hysteresis in the perovskite solar cell have been investigated with both in situ transient photovoltage/photocurrent measurements and the semiconductor device simulation. Time-dependent behaviors of intensity and direction of the photocurrent and photovoltage are observed under the steady-state bias voltages and open-circuit conditions. These charge processes reveal the electric properties of the cell, demonstrating evolutions of both strength and direction of the internal electric field during the hysteresis. Further calculation indicates that this behavior is mainly attributed to both the interfacial doping and defect effects induced by the ion accumulation, which may be the origins for the general hysteresis in this cell.

Easily accessible polymer additives for tuning the crystal-growth of perovskite thin-films for highly efficient solar cells

For perovskite solar cells (Pero-SCs), one of the key issues with respect to the power conversion efficiency (PCE) is the morphology control of the perovskite thin-films. In this study, an easily-accessible additive polyethylenimine (PEI) is utilized to tune the morphology of CH3NH3PbI3-xClx. With addition of 1.00 wt% of PEI, the smoothness and crystallinity of the perovskite were greatly improved, which were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). A summit PCE of 14.07% was achieved for the p-i-n type Pero-SC, indicating a 26% increase compared to those of the devices without the additive. Both photoluminescence (PL) and alternating current impedance spectroscopy (ACIS) analyses confirm the efficiency results after the addition of PEI. This study provides a low-cost polymer additive candidate for tuning the morphology of perovskite thin-films, and might be a new clue for the mass production of Pero-SCs.

Simple biphenyl or carbazole derivatives with four di(anisyl)amino substituents as efficient hole-transporting materials for perovskite solar cells

Power conversion efficiencies of 13.6% and 11.5% were achieved in perovskite solar cells with two simple and readily accessible biphenyl or carbazole derivatives as hole-transporting materials.

Perovskite solar cells fabricated using dicarboxylic fullerene derivatives

Perovskite solar cells were fabricated using a novel benzoic acid fullerene bis adduct material (BAFB). The BAFB material was found to be a promising material for use in perovskite hybrid organic–inorganic solar cells. The efficiency was reported to be 9.63% for perovskite solar cells.

Triple cathode buffer layers composed of PCBM, C60, and LiF for high-performance planar perovskite solar cells

In this paper, triple cathode buffer layers (CBLs) composed of phenyl-C61-butyric acid methyl ester (PCBM), C60, and LiF layers were introduced into the planar p-i-n perovskite solar cells (p-i-n PSCs) with a device structure of ITO/PEDOT:PSS/CH3NH3PbI3-xClx/CBLs/Al. For comparison, a single CBL of PCBM and a double CBL of PCBM/LiF were also investigated in the p-i-n PSCs. On the basis of the PCBM buffer layer, the addition of a thin LiF layer facilitated the charge collection process and led to the dramatic improvement of the power conversion efficiency (PCE) of the PSCs up to 14.69% under an illumination of AM 1.5G, 100 mW/cm(2), which is to date one of the highest efficiencies of the p-i-n PSCs. By further insertion of a C60 layer between PCBM and LiF in the triple CBLs, a PCE of 14.24% was obtained, and more importantly, the PCBM/C60/LiF triple CBLs are very helpful for improving the stability of the devices and making the LiF layer less thickness-sensitive for achieving high performances of the p-i-n PSCs.

Sprayed P25 scaffolds for high-efficiency mesoscopic perovskite solar cells

Uniform, thickness-controllable and large-size mesoscopic TiO₂ films have been prepared by a spray method by using commercial P25 nanoparticles, yielding high efficiency for perovskite solar cells.