Dual-Functional Enantiomeric Compounds as Hole-Transporting Materials and Interfacial Layers in Perovskite Solar Cells

Abstract

In this paper, we describe the application of the enantiomeric compounds YLC-1−YLC-4, each featuring a bulky spiro[fluorene-9,9′-phenanthren]-10′-one moiety, as both hole-transporting materials (HTMs) and interfacial layers in both n−i−p and p−i−n perovskite solar cells (PSCs). These HTMs contain an enantiomeric mixture and a variety of core units linked to triarylamine donors to extend the degree of π-conjugation. The n−i−p PSCs incorporating YLC-1(a) exhibited a power conversion efficiency (PCE) of 19.15% under AM 1.5G conditions (100 mW cm −2 ); this value was comparable with that obtained using spiro-OMeTAD as the HTM (18.25%). We obtained efficient and stable p−i−n PSCs having the dopant-free structure indium tin oxide (ITO)/NiO x /interfacial layer (YLC)/perovskite/PC 61 BM/BCP/Ag. The presence of the spiro-based compounds YLC-1 and YLC-2 efficiently passivated the interfacial and grain boundary defects of the perovskite and enhanced the sizes of its grains, more so than did YLC-3 and YLC-4. These spiro-based YLC derivatives packed densely and functioned as Lewis bases to coordinate Pb and Ni ions in the perovskite and NiO x layers, respectively. Together, the effects of smaller grain boundaries and defect passivation of the perovskite enhanced the optoelectronic properties of the PSCs. The photoinduced charge carrier extraction in the linearly increasing voltage (photo-CELIV) curves of NiO x /YLC-1(a) showed the faster carrier transport 3.3 × 10 −3 cm 2 V −1 s −1 , which improved the carrier mobility, supporting the notion of defect passivation of the perovskite. The best-performing NiO x /YLC-1(a) device provided a short-circuit current density (J SC ) of 22.88 mA cm −2 , an open-circuit voltage (V OC ) of 1.10 V, and a fill factor (FF) of 80.93%, corresponding to an overall PCE of 20.37%. In addition, the PCEs of the NiO x /YLC-1(a) and NiO x /YLC-4(b) PSC devices underwent decays of only 98.1 and 97.0% of their original values after 41 days under an Ar atmosphere. Thus, these YLC derivatives passivated the NiO x surface and optimized the film quality of perovskites, thereby leading to superior PCEs of their respective PSCs.

Efficient and Stable Inverted Perovskite Solar Cells Using Donor–Acceptor–Donor Small Molecules to Tuning NiOx/Perovskite Interfacial Microstructure

“…When the leakage current of the battery is smaller, the corresponding short-circuit current density is larger. [31][32][33] The test results of the dark state are also consistent with the measurement The long-term environmental stability is the key to the future commercialization of PSCs. Unpackaged devices were stored at 30 AE 5% RH and 25 °C, and their performance was occasionally tested over a range of more than 1000 h to evaluate device stability, as shown in Figure 6a-d.…”

“…The devices based on NiO x / TBT films have smaller leakage currents than those based on NiO x . When the leakage current of the battery is smaller, the corresponding short-circuit current density is larger [31][32][33]. The test results of the dark state are also consistent with the measurement…”

“…[31] Based on spiro [fluorene-9,9 0 -phenanthrene-10 0 -1] derivatives (YLCs) that were introduced at the NiO x /perovskite interface to coordinate Pb 2þ , improve the carrier transport speed and increase the PCE to 20.37%. [32] P-type semiconductor 4,4 00 -bis(diphenylamine)-[1,1 0 :3 0 ,1 00 -terphenyl]-5 0 -carboxylic acid (TBP-BA) was used to modify NiO x /perovskite interface to promote hole transfer between the perovskite and NiO x layers by reducing the interfacial energy band offset and increase the PCE to 22.25%. [33] Ultrafast charge separation of p-type small molecules [triphenylamine-2,1,3-benzothiadiazole-triphenylamine (TBT)] has been investigated.…”

A route to carbon-sp3 bridging spiro-molecules: synthetic methods and optoelectronic applications

“…Remarkably, both configurations achieved impressive PCEs of 19.15% and 20.37% respectively. 172 These results provide preliminary confirmation of the potential of carbonyl-embedded spiro molecules in PSCs. However, the range of available carbonyl-embedded spiro molecules is currently limited, and further development is necessary to expand their variety and application possibilities in the field of PSCs.…”

Enhancement of Efficiency of Perovskite Solar Cells with Hole-Selective Layers of Rationally Designed Thiazolo[5,4-d]thiazole Derivatives

“…The interfaces between the perovskite and the HSL are responsible for most performance losses and interfacial instability in p–i–n PSCs. , Modification of the HSL/perovskite interface allows to improve energy level alignment, regulate perovskite crystallization, and reduce interfacial defects. , Efficient HSL design entails selecting building blocks with high T g and μ h values, as well as suitable ionization potentials and surface energies . Moreover, these HSLs can serve as defect passivation layers (i.e., IFL) to enhance the performance of PSCs using traditional HTLs such as nickel oxide (NiO x ), [2-(9 H -carbazol-9-yl)­ethyl]­phosphonic acid (2PACz), and [2­(3,6-dimethoxy-9 H -carbazol-9-yl)­ethyl]­phosphonic acid (MeO-2PACz). − In this study, we introduce PSCs utilizing 2PACz and TT derivatives as materials for HSL.…”