RESUMEN
Solution processed poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) transparent electrodes (TEs) offer great potential as a low cost alternative to expensive indium tin oxide (ITO). However, strong acids are typically used for enhancing the conductivity of PEDOT:PSS TEs, which produce processing complexity and environmental issues. This work presents an environmentally friendly acid free approach to enhance the conductivity of PEDOT:PSS using a light oxygen plasma treatment, in addition to solvent blend additives and post treatments. The plasma treatment was found to significantly reduce the sheet resistance of PEDOT:PSS TEs from 85 to as low as 15 Ω sq-1, which translates to the highest reported conductivity of 5012 S/cm for PEDOT:PSS TEs. The plasma treated PEDOT:PSS TE resulted in an ITO-free perovskite solar cell efficiency of 10.5%, which is the highest reported efficiency for ITO-free perovskite solar cells with a PEDOT:PSS electrode that excludes the use of acid treatments. This research presents the first demonstration of this technology. Moreover, the PEDOT:PSS TEs enabled better charge extraction from the perovskite solar cells and reduced hysteresis in the current density-voltage (J-V) curves.
RESUMEN
An optimal small amount of water added into methyl ammonium iodide (MAI) solution in isopropyl alcohol (IPA) helps perovskite crystallization and leads to larger grain size from sequential deposition of perovskite films. The concentration of water was varied from 1% to 7% (vol% of IPA) in MAI solution and optical absorption, crystallization, morphology of perovskite films and their photovoltaic performance were studied in perovskite solar cells. 5% by volume was found to lead to preferential crystallization in the (110) plane with grain size about three times that of perovskite films prepared without adding water into the MAI solution. The optimal water concentration of 5% by volume in the MAI solution led to average perovskite grain size of â¼600 nm and solar cell efficiency of 12.42% at forward scan with a rate of 0.5 V s(-1). Device performance decreases after increasing water concentration beyond 5% in the MAI solution due to formation of the PbI2 phase. Transient photocurrent and photovoltage measurements show the shortest charge transport time at 0.99 µs and the longest charge carrier life time at 13.6 µs for perovskite films prepared from 5% water in MAI solution, which improved perovskite solar cell efficiency from 9.04% to 12.42%.
RESUMEN
A conjugated copolymer based on alternating benzo[1,2-b;3,4-b']dithiophene (BDT) donor and dodecyloxy substituted benzo[c][1,2,5]thiadiazole (ABT) acceptor units was prepared for application in organic solar cells. A power conversion efficiency (PCE) of ~3% with a short-circuit current (Jsc) of 7.63 mA cm(-2), an open-circuit voltage (Voc) of 0.71 V and a fill-factor (FF) of 53.74% was obtained under the illumination of AM 1.5 solar irradiation (100 mW cm(-2)). Photovoltaic devices and their transient properties with a blend of the copolymer and the [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) at different ratios were studied using transient photovoltage (TPV), transient photocurrent (TPC) and atomic force microscopy (AFM) measurements. From the TPV and TPC measurements, the charge recombination times (τn) were found to be 21.1 µs, 12.6 µs and 10.5 µs, and the charge transport times (τd) were 1316 ns, 422 ns and 707 ns for the 1 : 0.5, 1 : 1 and 1 : 2 donor/acceptor (D/A) ratios, respectively. The 1 : 1 D/A ratio showed the shortest charge transport time (τd) and the longest charge diffusion length (Ln) according to L(n) [proportionality] â[τ(n)/τ(d)], leading to the highest device performance among the three ratios.