In several photovoltaic (PV) technologies, the presence of electronic defects within the semiconductor band gap limit the efficiency, reproducibility, as well as lifetime. Metal halide perovskites ...(MHPs) have drawn great attention because of their excellent photovoltaic properties that can be achieved even without a very strict film‐growth control processing. Much has been done theoretically in describing the different point defects in MHPs. Herein, we discuss the experimental challenges in thoroughly characterizing the defects in MHPs such as, experimental assignment of the type of defects, defects densities, and the energy positions within the band gap induced by these defects. The second topic of this Review is passivation strategies. Based on a literature survey, the different types of defects that are important to consider and need to be minimized are examined. A complete fundamental understanding of defect nature in MHPs is needed to further improve their optoelectronic functionalities.
Watching the defects: Defects play a pivotal role in the overall performance of perovskite solar cells. This Review focuses on central questions of “what defects exist in metal halide perovskites” and “how can one reduce detrimental defects towards high‐performance perovskite solar cells”.
Iodine vacancies (VI) and undercoordinated Pb2+ on the surface of all‐inorganic perovskite films are mainly responsible for nonradiative charge recombination. An environmentally benign material, ...histamine (HA), is used to passivate the VI in perovskite films. A theoretical study shows that HA bonds to the VI on the surface of the perovskite film via a Lewis base–acid interaction; an additional hydrogen bond (H‐bond) strengthens such interaction owing to the favorable molecular configuration of HA. Undercoordinated Pb2+ and Pb clusters are passivated, leading to significantly reduced surface trap density and prolonged charge lifetime within the perovskite films. HA passivation also induces an upward shift of the energy band edge of the perovskite layer, facilitating interfacial hole transfer. The combination of the above raises the solar cell efficiency from 19.5 to 20.8 % under 100 mW cm−2 illumination, the highest efficiency so far for inorganic metal halide perovskite solar cells (PSCs).
An environmentally benign material, histamine (HA), is used to intentionally passivate the VI in the CsPbI3−xBrx perovskite thin films. The synergistic effect of Lewis base–acid interaction and H‐bond strengthens the adsorption of HA molecules on the surface of perovskite. The fabricated PSCs with HA passivation significantly reduced the number of uncoordinated Pb2+ and achieved a record 20.8 % efficiency.
Single crystalline perovskites exhibit high optical absorption, long carrier lifetime, large carrier mobility, low trap-state-density and high defect tolerance. Unfortunately, all single crystalline ...perovskites attained so far are limited to bulk single crystals and small area wafers. As such, it is impossible to design highly demanded flexible single-crystalline electronics and wearable devices including displays, touch sensing devices, transistors, etc. Herein we report a method of induced peripheral crystallization to prepare large area flexible single-crystalline membrane (SCM) of phenylethylamine lead iodide (C
H
C
H
NH
)
PbI
with area exceeding 2500 mm
and thinness as little as 0.6 μm. The ultrathin flexible SCM exhibits ultralow defect density, superior uniformity and long-term stability. Using the superior ultrathin membrane, a series of flexible photosensors were designed and fabricated to exhibit very high external quantum efficiency of 26530%, responsivity of 98.17 A W
and detectivity as much as 1.62 × 10
cm Hz
W
(Jones).
Abstract
The organic-inorganic hybrid lead halide perovskites have emerged as a series of star materials for solar cells, lasers and detectors. However, the issues raised by the toxic lead element ...and marginal stability due to the volatile organic components have severely limited their potential applications. In this work, we develop a nucleation-controlled solution method to grow large size high-quality Cs
3
Bi
2
I
9
perovskite single crystals (PSCs). Using the technique, we harvest some centimeter-sized single crystals and achieved high device performance. We find that X-ray detectors based on PSCs exhibit high sensitivity of 1652.3 μC Gy
air
−1
cm
−2
and very low detectable dose rate of 130 nGy
air
s
−1
, both desired in medical diagnostics. In addition, its outstanding thermal stability inspires us to develop a high temperature X-ray detector with stable response at up to 100 °C. Furthermore, PSCs exhibit high X-ray imaging capability thanks to its negligible signal drifting and extremely high stability.
Recently, lead halide‐based perovskites have become one of the hottest topics in photovoltaic research because of their excellent optoelectronic properties. Among them, organic‐inorganic hybrid ...perovskite solar cells (PSCs) have made very rapid progress with their power conversion efficiency (PCE) now at 23.7 %. However, the intrinsically unstable nature of these materials, particularly to moisture and heat, may be a problem for their long‐term stability. Replacing the fragile organic group with more robust inorganic Cs+ cations forms the cesium lead halide system (CsPbX3, X is halide) as all‐inorganic perovskites which are much more thermally stable and often more stable to other factors. From the first report in 2015 to now, the PCE of CsPbX3‐based PSCs has abruptly increased from 2.9 % to 17.1 % with much enhanced stability. In this Review, we summarize the field up to now, propose solutions in terms of development bottlenecks, and attempt to boost further research in CsPbX3 PSCs.
Thermally stable and able: All‐inorganic CsPbX3 perovskites (X is halide) have attracted attention owing to their thermally stability for photovoltaic applications. This Review presents the various CsPbX3 materials and the challenges as well as perspectives for the future development of CsPbX3 solar cells.
All‐inorganic CsPbBrI2 perovskite has great advantages in terms of ambient phase stability and suitable band gap (1.91 eV) for photovoltaic applications. However, the typically used structure causes ...reduced device performance, primarily due to the large recombination at the interface between the perovskite, and the hole‐extraction layer (HEL). In this paper, an efficient CsPbBrI2 perovskite solar cell (PSC) with a dimensionally graded heterojunction is reported, in which the CsPbBrI2 material is distributed within bulk–nanosheet–quantum dots or 3D–2D–0D dimension‐profiled interface structure so that the energy alignment is optimized in between the valence and conduction bands of both CsPbBrI2 and the HEL layers. Specifically, the valence‐/conduction‐band edge is leveraged to bend with synergistic advantages: the graded combination enhances the hole extraction and conduction efficiency with effectively decreased recombination loss during the hole‐transfer process, leading to an enhanced built‐in electric field, hence a high VOC of as much as 1.19 V. The profiled structure induces continuously upshifted energy levels, resulting in a higher JSC of as much as 12.93 mA cm−2 and fill factor as high as 80.5%, and therefore record power conversion efficiency (PCE) of 12.39%. As far as it is known, this is the highest PCE for CsPbBrI2 perovskite‐based PSC.
Here, a 3D–2D–0D multi‐graded interface based on CsPbBrI2 bulk, nanosheets, and quantum dots is first designed for CsPbBrI2 perovskite solar cells. Such a multigraded surface favorably reduces the recombination at the CsPbBrI2/polybis(4‐phenyl) (2,4,6‐trimethylphenyl)amine interface, resulting in a record stabilized power conversion efficiency of 12.39%, a nearly 20% increase compared with 10.38% for ungraded devices.
Owing to their superior thermal stability, metal halide inorganic perovskite materials continue to attract interest for photovoltaics applications. The highest reported power conversion efficiency ...(PCE) for solar cells based on inorganic perovskites is over 20 %. As this PCE corresponds to 73 % of the theoretical limit, there remains more room for further improving the device PCEs than for improving organic–inorganic hybrid perovskite solar cells (PSCs). The main loss is in the photovoltage, which is limited by interfaces in terms of non‐radiative recombination caused by traps and energy‐level mismatch. Furthermore, inefficient charge extraction at interfacial contacts reduces the photocurrent and fill factor. This Minireview summarizes the recent developments in the fundamental understanding of how the interfaces and interfacial layers influence the performance of solar cells based on inorganic perovskite absorbers. An outlook for the development of highly efficient and stable inorganic PSCs from the interface point of view is also given.
This Minireview summarizes the recent developments on interfaces in inorganic perovskite solar cells, with special focus on the fundamental understanding of how interfaces influence the performance of devices. Directions for developing highly efficient and stable inorganic perovskite solar cells by interface engineering are also provided.
Flexible perovskite solar cells have attracted widespread research effort because of their potential in portable electronics. The efficiency has exceeded 18 % owing to the high‐quality perovskite ...film achieved by various low‐temperature fabrication methods and matching of the interface and electrode materials. This Review focuses on recent progress in flexible perovskite solar cells concerning low‐temperature fabrication methods to improve the properties of perovskite films, such as full coverage, uniform morphology, and good crystallinity; demonstrated interface layers used in flexible perovskite solar cells, considering key figures‐of‐merit such as high transmittance, high carrier mobility, suitable band gap, and easy fabrication via low‐temperature methods; flexible transparent electrode materials developed to enhance the mechanical stability of the devices; mechanical and long‐term environmental stability; an outlook of flexible perovskite solar cells in portable electronic devices; and perspectives of commercialization for flexible perovskite solar cells based on cost.
Flexible perovskite solar cells have attracted significant attention owing to their promising potential in practical applications. This Review discusses the prerequisite conditions for flexible perovskite solar cells, provides an outlook of flexible perovskite devices in portable electronic products, and estimates their production cost by roll‐to‐roll vacuum deposition for commercialization.
Flexible perovskite solar cells (f‐PSCs) have attracted great attention because of their unique advantages in lightweight and portable electronics applications. However, their efficiencies are far ...inferior to those of their rigid counterparts. Herein, a novel histamine diiodate (HADI) is designed based on theoretical study to modify the SnO2/perovskite interface. Systematic experimental results reveal that the HADI serves effectively as a multifunctional agent mainly in three aspects: 1) surface modification to realign the SnO2 conduction band upward to improve interfacial charge extraction; 2) passivating the buried perovskite surface, and 3) bridging between the SnO2 and perovskite layers for effective charge transfer. Consequently, the rigid MA‐free PSCs based on the HADI‐SnO2 electron transport layer (ETL) display not only a high champion power conversion efficiency (PCE) of 24.79% and open‐circuit voltage (VOC) of 1.20 V but also outstanding stability as demonstrated by the PSCs preserving 91% of their initial efficiencies after being exposed to ambient atmosphere for 1200 h without any encapsulation. Furthermore, the solution‐processed HADI‐SnO2 ETL formed at low temperature (100 °C) is utilized in f‐PSCs that achieve a PCE as high as 22.44%, the highest reported PCE for f‐PSCs to date.
Herein, a novel histamine diiodate (HADI) is synthesized and incorporated into the SnO2/perovskite interface to modulate its electronic properties. Experimental results and theoretical calculations demonstrate a bridge function of HADI. The HADI‐SnO2‐based rigid/flexible perovskite solar cells (PSCs) achieve efficiencies of 24.79% and 22.44%, respectively, the highest reported values for rigid MA‐free PSCs and flexible PSCs so far.
Inorganic perovskite based solar cells (PSCs) have been receiving unprecedented attention worldwide in the past several years due to their higher intrinsic stability towards high temperatures and ...high theoretical power conversion efficiencies. Since a photovoltaic performance of 20.37% has been achieved for inorganic PSCs recently, the operational stability of these devices has become the major bottleneck which impedes their commercialization. The high thermal stability associated with inorganic perovskites comes along with poorer phase stability compared to their hybrid counterparts and therefore needs thorough understanding. Lattice strain and vacancies within the perovskite crystals are found to be the origin of these phase instability issues. This review summarizes the progress in stability research on inorganic perovskites. Specifically, the degradation mechanisms of inorganic perovskites towards temperature, moisture and oxygen are summarized and discussed. Solutions for tackling these stability issues are reviewed and an outlook on further strategies is provided.
The composition, light, moisture and oxygen all affect the stability of metal halide inorganic perovskites, whose degradation mechanisms are significantly different from those of hybrid perovskites.
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