shuhui

2D perovskite stabilized phase-pure formamidinium perovskite solar cells

2D perovskite stabilized phase-pure formamidinium perovskite solar cells, Published online: 01 August 2018; doi:10.1038/s41467-018-05454-4

Utilizing mixed-cation-halide can improve stability of the formamidinium perovskite films and devices but sacrifices the photocurrent due to an increase in bandgap. Here Lee et al. introduced small amounts of 2D perovskite to obtain high efficiency and stability based on phase-pure formamidinium based perovskite.

Optical transfer matrix formalism simulation is used to model the absorption spectra, exciton generation rate, and optical electric field distribution of the polymer solar cells based on PTB7‐Th:PC₇₁BM. High performance devices are obtained under the guidance of optical transfer matrix formalism simulation. An optimum PCE of 10.60% is obtained with the device based on the WO_x‐HfAcac buffer layer.

Light management is important for improving light absorption within active layers in polymer solar cells (PSCs). Electrode buffer layers play an important role in modulating the distribution of optical electric filed within the photoactive layer. Herein, the authors employ solution‐processed WO_x or ReO_x to substitute the acidic poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as the anode buffer layer and ZrAcac or HfAcac to replace Mg as the cathode buffer layer. Optical transfer matrix formalism simulation is used to model the absorption spectra, exciton generation rate, and optical electric field distribution of devices. Simulated results shows that stronger absorption, quicker exciton generation rate, and more reasonable photoelectric field distribution can be achieved in the photoactive layer with solution‐processed buffer layer modification, which results in a higher short‐circuit current density (J _sc). Under the guidance of theoretical simulation, the device with architecture of ITO/WO_x/PTB7‐Th:PC₇₁BM/HfAcac/Al is optimized. Compared with the traditional PEDOT:PSS‐Mg based device, the J _sc is increased from 16.60 to 18.61 mA cm⁻² and the best power conversion efficiency (PCE) is increased from 9.02% to 10.60% for the device with WO_x‐HfAcac modification, which is among the best values reported for fullerene‐based PSCs. The good agreement between simulated and experimental results indicates that optical model is a useful tool for device design and optimization.

Chloroplatinic acid (H₂PtCl₆) is incorporated into the TiO2 precuror to improve the electrical properties of a compact TiO2 film with the aim to improve the charge carrier extraction and injection efficiency in n‐i‐p perovskite solar cells. As a result, the resulting perovskite solar cells presented a maximum power conversion efficiency as high as 20.05% owing to the obvious improvements of open‐circuit voltages (1.15 V) and fill factor (0.75).

The electron‐transporting layer (ETL) plays a critical role in improving the charge extraction and suppressing the carrier recombination in planar perovskite solar cells (PSCs). Compact titanium dioxide (TiO₂) film is a widely used as an ETL in conventional n‐i‐p PSCs. However, there is still much room for improvement in the electron mobility and reducing the oxygen vacancies of the compact TiO₂ film. Herein, Pt‐doped TiO₂ film with outstanding electron‐transporting property and complete coverage on the substrates is reported by the authors. Pt‐doping results in a tailed band level of TiO₂, which could suppress the charge accumulation at the interface of TiO₂‐Pt/perovskite. Consequently, TiO₂‐Pt ETL based PSCs deliver a power conversion efficiency as high as 20.05% with an open‐circuit voltage of 1.15 V, a fill factor of 0.75, a short‐circuit current density of 23.83 mA cm⁻² and remarkably alleviated hysteresis behavior.

High efficiency planar-type perovskite solar cells with negligible hysteresis using EDTA-complexed SnO₂

High efficiency planar-type perovskite solar cells with negligible hysteresis using EDTA-complexed SnO₂, Published online: 13 August 2018; doi:10.1038/s41467-018-05760-x

The development of high efficiency planar-type perovskite solar cell has been lagging behind the mesoporous-type counterpart. Here Yang et al. modify the oxide based electron transporting layer with organic acid and obtain planar-type cells with high certified efficiency of 21.5% and decent stability.

Advanced Functional Materials, Volume 28, Issue 40, October 4, 2018.

Advanced Functional Materials, EarlyView.

Angewandte Chemie International Edition, EarlyView.

Advanced Functional Materials, Volume 28, Issue 31, August 1, 2018.

Angewandte Chemie International Edition, EarlyView.

Angewandte Chemie International Edition, EarlyView.

Angewandte Chemie International Edition, EarlyView.

Publication date: October 2018

Source: Nano Energy, Volume 52

Author(s): Dongliang Bai, Hui Bian, Zhiwen Jin, Haoran Wang, Lina Meng, Qian Wang, Shengzhong (Frank) Liu

Abstract

Graphical abstract

Advanced Energy Materials, July 2018.

Visualization and suppression of interfacial recombination for high-efficiency large-area pin perovskite solar cells

Visualization and suppression of interfacial recombination for high-efficiency large-area pin perovskite solar cells, Published online: 30 July 2018; doi:10.1038/s41560-018-0219-8

Non-radiative recombination is a critical limiting factor for perovskite solar cell performance. Stolterfoht et al. visualize the various recombination pathways in planar pin cells with photoluminescence imaging and use it to design improved solar cells with 1 cm2 areas and ~20% efficiency.

The intricate coherent interplay of excitons, spins, and phonons in 2D perovskites (C₆H₅C₂H₄NH₃)₂PbI₄ are studied using transient optical spectroscopy. New insights into the hotly debated origins of transient spectral features, exciton dynamics, and relaxation pathways; ultrafast spin relaxation; and coherent exciton–phonon coupling are revealed from the detailed phenomenological modeling of the transient dynamics.

Abstract

Layered 2D halide perovskites with their alternating organic and inorganic atomic layers that form a self‐assembled quantum well system are analogues of the purely inorganic 2D transition metal dichalcogenides. Within their periodic structures lie a hotbed of photophysical phenomena such as dielectric confinement effect, optical Stark effect, strong exciton–photon coupling, etc. Detailed understanding into the strong light–matter interactions in these hybrid organic–inorganic semiconductor systems remains modest. Herein, the intricate coherent interplay of exciton, spin, and phonon dynamics in (C₆H₅C₂H₄NH₃)₂PbI₄ thin films using transient optical spectroscopy is explicated. New insights into the hotly debated origins of transient spectral features, relaxation pathways, ultrafast spin relaxation via exchange interaction, and strong coherent exciton–phonon coupling are revealed from the detailed phenomenological modeling. Importantly, this work unravels the complex interplay of spin–quasiparticle interactions in these layered 2D halide perovskites with large spin–orbit coupling.

Dipolar cations confer defect tolerance in wide-bandgap metal halide perovskites

Dipolar cations confer defect tolerance in wide-bandgap metal halide perovskites, Published online: 06 August 2018; doi:10.1038/s41467-018-05531-8

The performance of wide-bandgap perovskite photovoltaics is limited by the undesired phase transition and high density of deep level traps. Here, Tan et al. incorporate dipolar methylammonium cation to make the material defect-tolerant and achieve a high power conversion efficiency of 20.7%.

Advanced Functional Materials, Volume 28, Issue 39, September 26, 2018.

Advanced Materials, Volume 30, Issue 38, September 20, 2018.

Advanced Materials, Volume 30, Issue 38, September 20, 2018.

Advanced Materials, Volume 30, Issue 38, September 20, 2018.

Advanced Materials, EarlyView.

Advanced Energy Materials, Volume 8, Issue 27, September 25, 2018.