Perovskites as a semiconductor are of profound interest and arguably, the investigation on the distinctive perovskite composition is paramount to fabricate efficient devices and solar cells.We probed the role of anion and cations and their impact on optoelectronic and photovoltaic properties. We report a machine learning approach to predict the bandgap and power conversion efficiency by employing eight different perovskites compositions. The predicted solar cell parameters validate the experimental data. The adopted Random forest model presented a good match with high R 2 scores of >0.99 and >0.82 for predicted absorption and J-V data sets respectively and showed minimal error rates with precise prediction of bandgap and power conversion efficiencies. Our results suggest that the machine learning technique is an innovative approach to aid the preparation of perovskite and can accelerate the commercial aspects of perovskite solar cells without fabricating working devices and minimizes the fabrication steps and save cost.

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Slowing the degradation of perovskite-based solar cells (PSCs) is of substantial interest. We engineered the surface by introducing a hydrophobic overlayer on a 3-dimensional perovskite using fluorinated or nonfluorinated aryl ammonium cation spacers. The placement of a fluoroarene cation allows the formation of a bilayer structure i.e., layered/3-dimensional perovskites. By doing so, the surface hydrophobic character increases notably by the virtue of perfluorinated benzene moiety. The fabricated devices thereof gave higher performance and longevity than control devices, in addition to mitigating reliability. The fluorophenethylammonium iodide (FPEAI) based devices showed lower non-radiative carrier recombination. To decipher the orientation of the spacer cation in this bilayer structure, we probed the surface by polarization-modulated infrared reflection-absorption spectroscopy and noted substantial differences in the orientation due to the presence of fluorine substitution. We hypothesize that the stronger van der Waals interactions due to the higher electronegativity in FPEAI govern the orientation, performance enhancement, and acts as a barrier to moisture decomposition.

We developed triple bonded π-conjugated zinc-phthalocyanine dimers (ZnPc-t-DPP-t-ZnPc 1, ZnPc-t-t-ZnPc 2, ZnPc-t-Spiro-t-ZnPc 3) through molecular engineering, these dimers were then employed as hole selective layers for perovskite solar cell.

Typically,m olecules with at wisted donor-acceptor (D-A) architecture have been exploited forc onstructing thermally activated delayed fluorescence( TADF) materials. Herein, we reportt he first example of at hiophene-based thermally activated delayedf luorescent molecule withoutaD-A architecture.C ompound 1 (2,5bis(2,2-di(thiophen-2-yl)vinyl)thiophene)i sc onformationally flexible and shows weakf luorescencei nt he solution state but displays bright TADFin both condensed and solid states. Compound 1 crystallized in two different polymorphs (1a and 1b). Interestingly,b oth polymorphs show distinctly different TADF features. The broad spectral features and the TADF characteristicso f1 have been explored for the time-dependent multicolor (green, yellow and red) imaging of living cells.Recently,f ully organic thermally activated delayed fluorescence (TADF) materials have attracted al ot of research interest owing to their potential applicationsi nt he field of display and lighting technology. [1] The well-accepted mechanism for TADF is that reverse intersystem crossing( rISC) from excited triplet state (T)t oe xcited singlet state (S 1 )a nd followed by radiative decay of spin allowed S 1 !S 0 transition. [1] However,t he rate of rISC depends highly on the spin-orbit coupling (SOC) and energy gap (DE ST )b etween the first excited triplet (T 1 )a nd singlet (S 1 )s tate. In purely organic fluorophores the SOC is very weak and thus, al ot of research effort has been devoted to modulating the DE ST value of fluorophores to achievei m-provedT ADF properties. [2] The most successful molecular design strategya dopted involves twisted donor-acceptor systems. As the DE ST value is directly proportional to the spatial overlap between the donor and acceptorm oieties, very small DE ST value can be achieved by spatially localizing the HOMO and LUMO orbitals of ad onor (D)-acceptor (A) system by increasingt he twist angle betweent he Da nd Am oieties. [1, 2] However, the large twist angle between the Da nd An ot only reduces the DE ST value but also limits oscillator strength and consequently reduces the overall luminescenceq uantum yield which is an important parameter forp ractical applications of TADF materials. Further,t oe nhancet he oscillator strengthn ew designs based on D-p-A and D-A-D architectures were explored. [3] The TADF properties of D-A systems can also be improvedb yi ntroducing internal/external heavier elements and halogen atoms such as Cl and Br to modulate the SOC. [4] It is important to note that all the design strategies described thitherto for developing organic TADF materials, mostly relied on molecular systems comprising donor and acceptor units. Surprisingly,T ADF emitter with an on-donor-acceptor architecture is very rarely realized. [4j] Thiophene, an aromatic heterocycle with heavier Sulphur atom has al ower stabilization energy (29 kcal mole À1 )c ompared to benzene (36 kcal mole À1 ). [5] Thus,t hiophene based oligomers and polymers exhibit high photoconductivity and have been used in l...