Dopant-Free Hole-Transporting Material with a C 3 h Symmetrical Truxene Core for Highly Efficient Perovskite Solar Cells

The rich molecular design of electron donor (D)–acceptor (A) polymers offers many valuable clues to obtain high‐efficiency hole‐transporting materials (HTMs) for use in perovskite solar cells (PVSCs). The fused aromatic or heteroaromatic units can increase the conjugation of the polymer backbone to facilitate electron delocalization, which increases the rigidity of adjacent units to prevent rotational disorder and lower the reorganization energy, leading to improved carrier mobility and optimized film morphology. In this work, fused‐ring ladder‐type indacenodithiophene and indacenodithieno[3,2‐b]thiophene are used as D units, benzodithiophene‐4,8‐dione as the A unit, and thienothiophene as a π‐bridge to form the D–A polymers PBDTT and PBTTT, respectively. Both polymers exhibit favorable properties as HTMs including suitable energy levels, high hole mobility, and excellent film quality. Both dopant‐free HTMs endow n‐i‐p PVSCs with promising performance and stability. A maximum power conversion efficiency of 20.28% is achieved for PBDTT‐based devices, which is among the highest values reported to date.

Section: Resultsmentioning

confidence: 99%

“…[1][2][3][4][5][6][7] Recently, PVSCs displaying maximum PCEs of over PCE of 19.06%. [1][2][3][4][5][6][7] Recently, PVSCs displaying maximum PCEs of over PCE of 19.06%.…”

Section: Introductionmentioning

confidence: 99%

Dopant‐Free, Donor–Acceptor‐Type Polymeric Hole‐Transporting Materials for the Perovskite Solar Cells with Power Conversion Efficiencies over 20%

You

Zhuang

Wang

et al. 2019

“…[255][256][257][258] We further note that the loss in performance is often related to the use of additives like Li-TFSI, tert-butylpyridine (tBP), and Co-complexes, necessary to oxidize the HTM and achieve high enough conductivities to ensure balanced charge extraction and maximum device performance. [259][260][261] Therefore, several HTMs have been developed that do not require these additives in order to obtain good performance. However, in general, devices without additives show lower PCEs than their counterparts containing the additives.…”

Section: Wwwadvancedsciencenewscommentioning

confidence: 99%

Capturing the Sun: A Review of the Challenges and Perspectives of Perovskite Solar Cells

Petrus

Schlipf

Cheng

et al. 2017

318

201

following statement: These materials can be processed from solution and yet exhibit optoelectronic materials properties described in classic solid-state physics textbooks. This unprecedented combination has led to photovoltaic devices that can be processed at room temperature and achieve performance levels similar to industry giant polycrystalline silicon, from a starting point of 3.8% in 2009. [1][2][3][4] The first light-emitting electrochemical cells [5] and diodes [6][7][8] have also been introduced recently, leading to tunable light emission spectra and internal quantum efficiencies exceeding 15%.The road towards these achievements has been marked by a constant improvement of perovskite deposition techniques fueled by our increasing understanding of the crystallization processes. The choice of deposition technique, either from solution or vapor, and the composition and order in which precursor species are applied has a great influence on the crystallization kinetics. Here, one can distinguish one-step methods where the perovskite is formed from a precursor mixture dissolved in a common solution, and two-step methods where the inorganic compound is deposited first and transformed to the perovskite phase later by addition of the organic constituents. [9][10][11] Furthermore, many parameters during processing can have an effect on the crystallization mechanism and consequently on film morphology, such as the choice of solvents, concentrations and processing additives that are often not incorporated into the final product. [11][12][13] We discuss this aspect in Section 2, where we focus our attention on the most commonly employed solution-based techniques. Additionally, as for any new technology trying to displace an incumbent technology, higher efficiencies, lower costs, reproducibility, stability, and sustainability are paramount. In particular, reproducibility has been a major challenge in perovskite solar cells from the beginning: small variations in morphology, like crystal size, film roughness, and pinholes can have detrimental effects on photovoltaic performance. [14] On the other hand, current-voltage measurements often showed a hysteresis that is rarely seen in other photovoltaic technologies. [15] These topics are highlighted in Sections 3 and 4. Finally, in Section 5 we discuss the framework for market introduction, such as cost reduction by choosing low-cost charge transport layers, or how the lifetime of perovskite absorbers can be extended by the choice of materials composition.Hybrid metal halide perovskites have become one of the hottest topics in optoelectronic materials research in recent years. Not only have they surpassed everyone's expectations and achieved similar performance as tried and true polycrystalline silicon photovoltaic devices, but they are also finding applications in a variety of different fields, including lighting. The main advantages of hybrid metal halide perovskites are simple processability, compatible with large-scale solution processing such as roll-to-roll printing, a...

“…It replaced amorphous NiO as the HTL in an inverted construction, and led to the highest PCE of 9.11% among planar perovskite solar cells based on an inorganic HTM at that time. [ 91 ] Copyright 2016, American Chemical Society. Obviously, NiO NC matches best with the valence band edge of CH 3 NH 3 PbI 3 (−5.4 eV).…”

Section: Hole Transport Materialsmentioning

confidence: 99%

The Progress of Interface Design in Perovskite‐Based Solar Cells

Fan

Huang

Wang

et al. 2016

147

117

Figure 20. a) Modeled J − V characteristics of a perovskite device comprising ions but no traps. b) Modeled I -V characteristics of perovskite devices comprising ions and no traps for varying ion densities. c) Modeled J − V characteristics of perovskite device comprising ions and traps with varying ion mobility as indicated in the legend at a sweep rate of 100 kV s −1 . d) Modeled J -V characteristics of a perovskite device comprising ions and bulk traps. [ 211 ] 2015, American Chemical Society. e) Flow directions of the charged ion species in a Pb|MAPbI 3 |AgI |Ag cell under electrical bias. f) Images for surfaces A and B and g) a scanning electron microscope (SEM) image of surface B on the Pb pellet. h) The same cell confi guration to Figure 23 e. i) Images of each pellets after aging at 50 °C for a week in Ar atmosphere (no current stressing). Reproduced with permission. [ 212 ]