Abstract
Inorganic p-type films with high mobility are very important for opto-electronic applications. It is very difficult to synthesize p-type films with a wider, tunable band gap energy and suitable band energy levels. In this research, p-type copper aluminum sulfide (CuxAl1−xSy) films with tunable optical band gap, carrier density, hole mobility and conductivity were first synthesized using a simple, low cost and low temperature chemical bath deposition method. These in situ fabricated CuxAl1−xSy films were deposited at 60 °C using an aqueous solution of copper(ii) chloride dihydrate (CuCl2·2H2O), aluminium nitrate nonohydrate [Al(NO3)3·9H2O], thiourea [(NH2)2CS], and ammonium hydroxide, with citric acid as the complexing agent. Upon varying the ratio of the precursor, the band gap of the CuxAl1−xSy films can be tuned from 2.63 eV to 4.01 eV. The highest hole mobility obtained was 1.52 cm2 V−1 s−1 and the best conductivity obtained was 546 S cm−1. The CuxAl1−xSy films were used as a hole transporting layer (HTL) in organic solar cells (OSCs), and a good performance of the OSCs was demonstrated using the CuxAl1−xSy films as the HTL. These results demonstrate the remarkable potential of CuxAl1−xSy as hole transport material for opto-electronic devices.
Highlights
Industrialization in the past years has yielded an increasing energy demand, which was resolved using non-renewable resources
Because of its high hygroscopicity and acidity,[15] PEDOT:PSS has an adverse impact on the device stability
Several materials with high transmissivity within the range of visible light have been used as alternatives, and these are materials such as molybdenum oxide (MoOx),[16,17,18] nickel oxide aKey Laboratory of Arti cial Micro- and Nano-structures of Ministry of Education of China, School of Physics and Technology, Wuhan University, Wuhan 430072, PR China bShenzhen Institute of Wuhan University, Shenzhen 518055, PR China
Summary
Chalcogenide (CuAlS2) which is known to be a p-type semiconductor, is a promising material because of its high band gap energy (Eg) and hole conductivity.[21,22] There are various methods used to prepare CuAlS2, such as chemical vapor transport deposition, solid phase reaction, solvothermal deposition, chemical spray pyrolysis, hydrothermal methods and chemical bath deposition (CBD).[23,24,25,26,27,28] these methods involve either high temperature or high pressure and the prepared CuAlS2 always has a low conductivity, whereas the lm prepared using CBD is not very uniform and lacks measureable electrical properties. With this method CuxAl1ÀxSy lms with a large area can be grown without using sophisticated instruments. Citric acid and ammonium hydroxide are used to adjust the speed of the reaction to obtain the required lm. $9H2O, 0.04 M (NH2)2CS, 0.02 M citric acid and pH adjuster (ammonium hydroxide) was used to prepare a CuAlS2 thin lm. CuCl2$2H2O, Al(NO3)3$9H2O and citric acid were placed into a beaker using deionized water as the solvent and stirred continuously for a few minutes until the solution became homogenous. Solution A and solution B were mixed together to obtain the nal solution, and ammonium hydroxide was added dropwise to adjust the pH to 8.8. The FTO substrates were placed into the nal solution at 60 C to obtain the required CuAlS2 lm. Yielded a power conversion efficiency (PCE) of 2.67% with an open-circuit voltage (Voc) of 0.596 V, a short-circuit current density (Jsc) of 9.21 mA cmÀ2, and a ll factor (FF) of 48.7%, which was comparable to that obtained with reference organic photovoltaics with PEDOT:PSS as HTL
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