Interfacial Kinetics of Efficient Perovskite Solar Cells
13 Aug 2017-Vol. 7, Iss: 8, pp 252
TL;DR: In this paper, the Nyquist spectra as a function of applied bias reveal the characteristic features of ion motion and accumulation that is mainly associated with the MA cations in MAPbI3.
Abstract: Perovskite solar cells (PSCs) have immense potential for high power conversion efficiency with an ease of fabrication procedure. The fundamental understanding of interfacial kinetics in PSCs is crucial for further improving of their photovoltaic performance. Herein we use the current-voltage (J-V) characteristics and impedance spectroscopy (IS) measurements to probe the interfacial kinetics on efficient MAPbI3 solar cells. We show that series resistance (RS) of PSCs exhibits an ohmic and non-ohmic behavior that causes a significant voltage drop across it. The Nyquist spectra as a function of applied bias reveal the characteristic features of ion motion and accumulation that is mainly associated with the MA cations in MAPbI3. With these findings, we provide an efficient way to understand the working mechanism of perovskite solar cells.
Citations
More filters
TL;DR: In this paper, the chemical composition of inorganic-organic hybrid perovskite materials is used to boost the performance and operational stability of perovsite solar cells (PSCs).
Abstract: Engineering the chemical composition of inorganic–organic hybrid perovskite materials is an effective strategy to boost the performance and operational stability of perovskite solar cells (PSCs). A...
95 citations
TL;DR: Electrochemical impedance spectroscopical analyses are used to study the time-dependent electrical characteristics of perovskite solar cells and demonstrate that both the dark and light ideality factors are sensitive to aging time, indicating the dominant existence of trap-assisted recombination in the investigated device.
Abstract: The last decade has witnessed the impressive progress of perovskite solar cells (PSCs), with power conversion efficiency exceeding 25%. Nevertheless, the unsatisfactory device stability and current-voltage hysteresis normally observed with most PSCs under operational conditions are bottlenecks that hamper their further commercialization. Understanding the electrical characteristics of the device during the aging process is important for the design and development of effective strategies for the fabrication of stable PSCs. Herein, electrochemical impedance spectroscopical (IS) analyses are used to study the time-dependent electrical characteristics of PSC. We demonstrate that both the dark and light ideality factors are sensitive to aging time, indicating the dominant existence of trap-assisted recombination in the investigated device. By analyzing the capacitance versus frequency responses, we show that the low-frequency capacitance increases with increasing aging time due to the accumulation of charges or ions at the interfaces. These results are correlated with the observed hysteresis during the current-voltage measurement and provide an in-depth understanding of the degradation mechanism of PSCs with aging time.
27 citations
TL;DR: In this paper, the state-of-the-art multiple-cation perovskites FA0.83MA0.17Pb(I 0.83Br 0.17)3 and Cs5(MA 0.3)3 were employed as absorber layers and investigated their intrinsic and interfacial dynamics in planar TiO2-based PSCs.
Abstract: Mixed-cation and halide perovskite solar cells have shown superior photovoltaic performance compared to mono-cation based representatives. Their remarkable photovoltaic performance is the effect of superior compositional engineering along with their unique optoelectronic properties. However, there is still a lack of understanding of the working principles of multi-cation based perovskite solar cells. In this study, we employ the state-of-the-art multiple-cation perovskites FA0.83MA0.17Pb(I0.83Br0.17)3 and Cs5(MA0.17FA0.83)95Pb(I0.83Br0.17)3 as absorber layers and investigate their intrinsic and interfacial dynamics in planar TiO2-based PSCs. We demonstrate that the incorporation of Cs+ in FA0.83MA0.17Pb(I0.83Br0.17)3 leads to an increase in power conversion efficiency, improved perovskite phase stability and reduced recombination. However, these devices along with these excellent characteristics still suffer from lower open circuit voltage (Voc) as compared to FA0.83MA0.17Pb(I0.83Br0.17)3 based devices. By analysing the morphological properties and capacitance versus frequency responses, we show that the higher grain size and higher accumulation of photogenerated charges lead to the high open circuit voltage in FA0.83MA0.17Pb(I0.83Br0.17)3 based devices. Our results demonstrate that the values of Voc not only depend on the recombination, but also on charge accumulation phenomena.
21 citations
TL;DR: In this paper, numerical simulations of optical and electrical properties of perovskite solar cells were conducted to quantify various losses like optical losses, recombination losses, and resistive losses against the Auger recombination induced practical efficiency limits.
Abstract: While the performance enhancement witnessed in the field of perovskite solar cells over the recent years has been impressive, a detailed analysis of various loss mechanisms is required for further performance optimization. Here, we address the same through numerical simulations of optical and electrical characteristics. We quantify various losses like optical losses (5%–6%), recombination losses (3%–4%), and resistive losses against the Auger recombination induced practical efficiency limits. Through this, we identify schemes to reduce these losses and hence lead to an increase in efficiency. In addition, we find that the optimum thickness of the perovskite (with material parameters comparable to MAPbI3-xClx and Eg = 1.55 eV) for solar cell fabrication is around 300 nm (comparable to the well-established value); however, the same could be as large as 900 nm for a trap free perovskite (∼ms as the minority carrier Shockley-Read-Hall recombination lifetime). The analyses also enable us to provide the design charts that could lead to >25% efficient perovskite solar cells on the planar structure.
19 citations
References
More filters
TL;DR: Two organolead halide perovskite nanocrystals were found to efficiently sensitize TiO(2) for visible-light conversion in photoelectrochemical cells, which exhibit strong band-gap absorptions as semiconductors.
Abstract: Two organolead halide perovskite nanocrystals, CH3NH3PbBr3 and CH3NH3PbI3, were found to efficiently sensitize TiO2 for visible-light conversion in photoelectrochemical cells. When self-assembled on mesoporous TiO2 films, the nanocrystalline perovskites exhibit strong band-gap absorptions as semiconductors. The CH3NH3PbI3-based photocell with spectral sensitivity of up to 800 nm yielded a solar energy conversion efficiency of 3.8%. The CH3NH3PbBr3-based cell showed a high photovoltage of 0.96 V with an external quantum conversion efficiency of 65%.
16,634 citations
TL;DR: It is shown that perovskite absorbers can function at the highest efficiencies in simplified device architectures, without the need for complex nanostructures.
Abstract: Many different photovoltaic technologies are being developed for large-scale solar energy conversion. The wafer-based first-generation photovoltaic devices have been followed by thin-film solid semiconductor absorber layers sandwiched between two charge-selective contacts and nanostructured (or mesostructured) solar cells that rely on a distributed heterojunction to generate charge and to transport positive and negative charges in spatially separated phases. Although many materials have been used in nanostructured devices, the goal of attaining high-efficiency thin-film solar cells in such a way has yet to be achieved. Organometal halide perovskites have recently emerged as a promising material for high-efficiency nanostructured devices. Here we show that nanostructuring is not necessary to achieve high efficiencies with this material: a simple planar heterojunction solar cell incorporating vapour-deposited perovskite as the absorbing layer can have solar-to-electrical power conversion efficiencies of over 15 per cent (as measured under simulated full sunlight). This demonstrates that perovskite absorbers can function at the highest efficiencies in simplified device architectures, without the need for complex nanostructures.
7,018 citations
TL;DR: Perovskite QD-sensitized 3.6 μm-thick TiO(2) film shows maximum external quantum efficiency (EQE) of 78.6% at 530 nm and solar-to-electrical conversion efficiency of 6.54% at AM 1.5G 1 sun intensity (100 mW cm(-2)), which is by far the highest efficiency among the reported inorganic quantum dot sensitizers.
Abstract: Highly efficient quantum-dot-sensitized solar cell is fabricated using ca. 2–3 nm sized perovskite (CH3NH3)PbI3 nanocrystal. Spin-coating of the equimolar mixture of CH3NH3I and PbI2 in γ-butyrolactone solution (perovskite precursor solution) leads to (CH3NH3)PbI3 quantum dots (QDs) on nanocrystalline TiO2 surface. By electrochemical junction with iodide/iodine based redox electrolyte, perovskite QD-sensitized 3.6 μm-thick TiO2 film shows maximum external quantum efficiency (EQE) of 78.6% at 530 nm and solar-to-electrical conversion efficiency of 6.54% at AM 1.5G 1 sun intensity (100 mW cm−2), which is by far the highest efficiency among the reported inorganic quantum dot sensitizers.
2,781 citations
TL;DR: The results of this combined computational and experimental study suggest that hybrid halide perovskites are mixed ionic–electronic conductors, a finding that has major implications for solar cell device architectures.
Abstract: Understanding the mechanism of ionic transport in organic–inorganic halide perovskites is crucial for the design of future solar cells. Here, Eames et al. undertake a combined experimental and computational study to elucidate the ion conducting species and help rationalize the unusual behaviour observed in these perovskite-based devices.
2,050 citations
TL;DR: Heavy doped inorganic charge extraction layers in planar PSCs were used to achieve very rapid carrier extraction, even with 10- to 20-nanometer-thick layers, avoiding pinholes and eliminating local structural defects over large areas.
Abstract: The recent dramatic rise in power conversion efficiencies (PCEs) of perovskite solar cells (PSCs) has triggered intense research worldwide. However, high PCE values have often been reached with poor stability at an illuminated area of typically less than 0.1 square centimeter. We used heavily doped inorganic charge extraction layers in planar PSCs to achieve very rapid carrier extraction, even with 10- to 20-nanometer-thick layers, avoiding pinholes and eliminating local structural defects over large areas. The robust inorganic nature of the layers allowed for the fabrication of PSCs with an aperture area >1 square centimeter that have a PCE >15%, as certified by an accredited photovoltaic calibration laboratory. Hysteresis in the current-voltage characteristics was eliminated; the PSCs were stable, with >90% of the initial PCE remaining after 1000 hours of light soaking.
1,936 citations