Tuning the energy level of TAPC: crystal structure and photophysical and electrochemical properties of 4,4'-(cyclohexane-1,1-diyl)bis[N,N-bis(4-methoxyphenyl)aniline]

Suppressing Excess Lead Iodide Aggregation and Reducing N-Type Doping at Perovskite/HTL Interface for Efficient Perovskite Solar Cells

Excess lead iodide (PbI2 ) aggregation at the charge carrier transport interface leads to energy loss and acts as unstable origins in perovskite solar cells (PSCs). Here, a strategy is reported to modulate the interfacial excess PbI2 by introducing π-conjugated small-molecule semiconductors 4,4'-cyclohexylbis[N,N-bis(4-methylphenyl)aniline] (TAPC) into perovskite films through an antisolvent addition method. The coordination of TAPC to PbI units through the electron-donating triphenylamine groups and π-Pb2+ interactions allows for a compact perovskite film with reduced excess PbI2 aggregates. Besides, preferred energy level alignment is achieved due to the suppressed n-type doping effect at the hole transport layer (HTL) interfaces. As a result, the TAPC-modified PSC based on Cs0.05 (FA0.85 MA0.15 )0.95 Pb(I0.85 Br0.15 )3 triple-cation perovskite achieved an improved PCE from 18.37% to 20.68% and retained ≈90% of the initial efficiency after 30 days of aging under ambient conditions. Moreover, the TAPC-modified device based on FA0.95 MA0.05 PbI2.85 Br0.15 perovskite produced an improved efficiency of 23.15% compared to the control (21.19%). These results provide an effective strategy for improving the performance of PbI2 -rich PSCs.

A flexible, multifunctional, optoelectronic anticounterfeiting device from high-performance organic light-emitting paper

As a primary anticounterfeiting technology, most paper anticounterfeiting devices take advantage of photoresponsive behaviors of certain security materials or structures, thus featuring low-security threshold, which has been a critical global issue. To incorporate optoelectronic devices into existing anticounterfeiting technology suggests a feasible avenue to address this challenge. Here we report a high-performance organic light-emitting paper-based flexible anticounterfeiting (FAC) device with multiple stimuli-responsiveness, including light, electricity, and their combination. Without sacrificing the preexisted security information on the paper, we fabricate FAC device in a facile, low-cost yet high-fidelity fashion by integrating patterned electro-responsive and photo-responsive organic emitters onto paper substrates. By introducing optical microcavities, the FAC device shows considerable color shift upon different viewing angle and applied voltage, which is easily discernible by naked eyes. Notably, the FAC device is bendable, unclonable, and durable (a half-lifetime over 4000 hours at 100 cd m^-2).