Copolymers of poly(3-thiopheneacetic acid) with poly(3-hexylthiophene) as hole-transporting material for interfacially engineered perovskite solar cell by modulating band positions for higher efficiency

Abstract

In order to tune the band positions of the hole-transporting material (HTM) in an interfacially engineered perovskite solar cell (PSC), random copolymers of poly(3-thiopheneacetic acid) and poly(3-hexylthiophene) (P3TAA-co-P3HT) with different compositions were produced by oxidative polymerization. The copolymers were characterized using 1H NMR, FTIR, and UV-vis spectroscopy and gel permeation chromatography. Here, ZnO nanoparticles were used as the electron-transporting material (ETM) and methylammonium lead iodide (MAPbI3) perovskite was used as the light-absorbing material to form an FTO/ZnO/MAPbI3/copolymer/Ag device, of which the power conversion efficiency (PCE) was found to be dependent on the copolymer composition and reached a maximum (∼10%) at a P3TAA content of 43 mol% in the copolymer (P3). The band gaps of the copolymers as determined from UV-vis spectroscopy and cyclic voltammetry exhibit a staggered-gap hetero-interface configuration in which the HOMO and LUMO of P3 closely match those of MAPbI3 and give rise to the maximum PCE. Time-resolved photoluminescence spectra of MAPbI3/HTM samples indicate that charge transfer across the perovskite/copolymer interface was faster with a reduced recombination rate for a P3 sample. The electrochemical impedance spectra (EIS) of the PSCs exhibit Nyquist plots with two semicircles, which correspond to an equivalent circuit consisting of two parallel R-C and R-CPE circuits connected in series. Analysis of the data indicates that the effective electron lifetime was longest for the P3 copolymer, which indicates that the charge recombination was lower than that in the components and other copolymers. The copolymers exhibited an intermediate stability with respect to their components, and amongst the copolymers P3 exhibited the highest stability.

Self-Powered Perovskite/CdS Heterostructure Photodetectors

“…These times are attributable to the different lifetimes of photocarriers on the surface and in the bulk, respectively. , To this end, the faster PL decay indicates efficient charge transfer at the heterointerface in agreement with the significantly quenched PL signal seen in Figure d. On the basis of this data, we conclude that the formed MAPbI 3 /CdS heterointerface promotes efficient charge transfer …”

“…On the basis of this data, we conclude that the formed MAPbI 3 /CdS heterointerface promotes efficient charge transfer. 52 Fabrication of MAPbI 3 /CdS Heterojunction Photodetector. Photodetector devices consisting of ITO/CdS/ MAPbI 3 /Au (Figure 3a−b) were fabricated with the CdS layer functioning as the ETL.…”

Direct Observation of Perovskite Photodetector Performance Enhancement by Atomically Thin Interface Engineering

“…Biexponential fits ( i = 2) were performed to quantify the carrier dynamics as shown by the blue trace in Figure b. As shown in the Supporting Information Figure S4, a slow component of 34 ns and a fast component of 9 ns in the WS 2 /perovskite heterostructure can be ascribed to bulk and surface photocarriers lifetime, respectively. , The much faster decay suggests rapid extraction of charge carriers across the interfaces. , Therefore, photogenerated electron and hole pairs are more efficiently quenched by introducing the WS 2 layer, and the shorter PL lifetime of the WS 2 /MAPbI 3 bilayer suggests that the heterostructure formation benefits the charge extraction at the interfaces …”

“…16,53 Therefore, photogenerated electron and hole pairs are more efficiently quenched by introducing the WS 2 layer, and the shorter PL lifetime of the WS 2 /MAPbI 3 bilayer suggests that the heterostructure formation benefits the charge extraction at the interfaces. 54 Carrier Transport in the Dark. Scanning a sequence of current maps under various bias voltages and fitting the results to a current−voltage (I−V) curve is a much more accurate way to provide information of the samples regarding the contact properties between sample and substrate, tip−sample interactions, local defects (especially at the edges), and the spatial fluctuation in local charge distributions.…”

Promotion Strategies of Hole Transport Materials by Electronic and Steric Controls for n–i–p Perovskite Solar Cells

“…[129] Shit et al introduced acetic acid substituent in P3HT polymer framework to withdraw electrons from the thiophene ring, also resulting in lower HOMO level closer to the one of perovskites, as compared with pristine P3HT (Figure 8 f). [127] Additionally, the regularity of the thiophene backbones was enhanced benefiting from the interchain and intrachain hydrogen bonding of acetic acid substituent in P3HT derivatives. To sum up, the introduction of electron-withdrawing groups in the organic conjugated materials is an efficient route to decrease their energy levels as well as improve crystallinity and regularity due to intermolecular interactions.…”