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Single-layer and multi-layer 2D polyimine films have been achieved through interfacial synthesis methods. However, it remains a great challenge to achieve the maximum degree of crystallinity in the 2D polyimines, which largely limits the long-range transport properties. Here we employ a surfactant-monolayer-assisted interfacial synthesis (SMAIS) method for the successful preparation of porphyrin and triazine containing polyimine-based 2D polymer (PI-2DP) films with square and hexagonal lattices, respectively. The synthetic PI-2DP films are featured with polycrystalline multilayers with tunable thickness from 6 to 200 nm and large crystalline domains (100-150 nm in size). Intrigued by high crystallinity and the presence of electroactive porphyrin moieties, the optoelectronic properties of PI-2DP are investigated by time-resolved terahertz spectroscopy. Typically, the porphyrin-based PI-2DP 1 film exhibits a p-type semiconductor behavior with a band gap of 1.38 eV and hole mobility as high as 0.01 cm 2  V -1  s -1 , superior to the previously reported polyimine based materials., (© 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

The bandgap of CuIn 1- x Ga x Se 2 (CIGS) chalcopyrite semiconductors can be tuned between ≈1.0 and ≈1.7 eV for Ga contents ranging between x = 0 and x = 1. While an optimum bandgap of 1.34 eV is desirable for achieving maximum solar energy conversion in solar cells, state-of-the-art CIGS-based devices experience a drop in efficiency for Ga contents x > 0.3 (i.e., for bandgaps >1.2 eV), an aspect that is limiting the full potential of these devices. The mechanism underlying the limited performance as a function of CIGS composition has remained elusive: both surface and bulk recombination effects are proposed. Here, the disentanglement between surface and bulk effects in CIGS absorbers as a function of Ga content is achieved by comparing photogenerated charge carrier dynamics in air/CIGS and surface-passivated ZnO/CdS/CIGS samples. While surface passivation prevents surface recombination of charge carriers for low Ga content (x < 0.3; up to 1.2 eV bandgap), surface recombination dominates for higher-bandgap materials. The results thus demonstrate that surface, rather than bulk effects, is responsible for the drop in efficiency for Ga contents larger than x ≈ 0.3., (© 2020 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)