research papers J. Appl. Cryst. (2016). 49 http://dx.doi.org/10.1107/S1600576716014552 1 of 10 Received 4 July 2016 Accepted 13 September 2016 Edited by F. Meilleur, Oak Ridge National Laboratory, USA, and North Carolina State University, USA Keywords: single-crystal growth; X-ray techniques; photoluminescence; piezoelectricity; Vickers microhardness. Supporting information: this article has supporting information at journals.iucr.org/j Growth and structural and physical properties of diisopropylammonium bromide molecular single crystals Harsh Yadav, a Nidhi Sinha, a,b * Sahil Goel, a Abid Hussain a and Binay Kumar a a Crystal Laboratory, Department of Physics and Astrophysics, University of Delhi, Delhi 110007, India, and b Department of Electronics, SGTB Khalsa College, University of Delhi, Delhi 110007, India. *Correspondence e-mail: nidhisinha5@yahoo.co.in Large single crystals of the promising molecular organic ferroelectric diiso- propylammonium bromide (DIPAB) have been grown by the solution technique. A structural study was performed using single-crystal X-ray diffraction analysis. The twin element of a selected DIPAB crystal was identified by a morphological study. Intermolecular interactions present in the grown crystal were explored by Hirshfeld surface (three-dimensional) and fingerprint plot (two-dimensional) studies. In UV–vis spectroscopy, the DIPAB crystal has shown high transparency with a wide direct band gap of 5.65 eV. In the photoluminescence spectrum, sharp UV and blue emissions were observed at 370, 392, 417 and 432 nm. The electrical properties were investigated by measuring the dielectric constant (") and loss (tan ) of the grown crystal. The DIPAB crystal exhibits a promising piezoelectric charge coefficient (d 33 ) value of 18 pC N 1 , which makes it suitable for transducer applications. A high ferroelectric Curie temperature (T c ’ 425 K) with high remnant polarization (20.52 mC cm 2 ) and high coercive field (12.25 kV cm 1 ) were observed in the as-grown crystal. Vickers microhardness analysis shows that the value of Meyer’s index (n = 7.27) belongs to the soft material range, which was also confirmed by void analysis along three crystallographic axes. It is shown that the DIPAB crystal has potential for optical, ferroelectric and piezoelectric applications. 1. Introduction Recently, new compounds of organic molecular ferroelectrics have been drawing attention owing to their eco-friendly processing, biocompatibility, light weight and mechanical flexibility, which make them suitable for optical and electronic devices (Horiuchi & Tokura, 2008; Li et al., 2013). Ferro- electric materials are electroactive, exhibiting a temperature- dependent reversible spontaneous polarization which can be switched by applying an electric field or mechanical force (Li et al., 2012). In order to work under severe thermal conditions, ferroelectric materials need to possess a high Curie tempera- ture (T c ) for various practical applications, such as in non- volatile random access memory devices, automotive electronic devices and power-generating industries (Chen et al., 2014). Piezoelectric materials possess a direct and indirect piezo- electric effect, which is suitable for ultrasonic transducers, microelectromechanical systems and sensor applications (Gonzalez-Macia et al., 2010). Advances in supramolecular crystal engineering are facilitating the design of highly effi- cient molecular materials for various applications. In such compounds, donor and acceptor molecules are simultaneously crystallized through intermolecular interactions to produce a spontaneous dipole moment (Tayi et al., 2012). Fu and co- ISSN 1600-5767 # 2016 International Union of Crystallography