Effect of Metal Doped Zinc Oxide Nanorods on Photoelectrical Characteristics of ZnO/Polyaniline Heterojunction Jyoti M. Ghushe 1 • Sushama M. Giripunje 2 • Subhash B. Kondawar 3 Received: 17 October 2015 / Accepted: 22 January 2016 / Published online: 27 January 2016 Ó Springer Science+Business Media New York 2016 Abstract The n-type vertically aligned metal doped ZnO nanorods (NRs) and p-type proton acid doped polyaniline (PANI) inorganic/organic heterojunction diodes have been fabricated. Aluminium (Al) and iron (Fe) doped ZnO NRs were grown on seed ZnO layer on fluorine doped tin oxide coated glass substrates by high temperature chemical bath deposition method. The elemental analysis using EDAX confirm doping of Al and Fe in ZnO. The morphology of doped ZnO nanorods and ZnO/PANI heterojunction exhibit well defined uniform nanorod arrays and interface between nanorods and polyaniline matrix respectively. The dark current–voltage curves confirmed the rectifying diode like behaviors of the heterojunctions, whereas under illumina- tion, the junction revealed good sensitivity to UV and visible range with increased current densities. The highest ideality factor and lowest barrier height was found for FeZnO/PANI heterojunction under dark and under light compared to that of ZnO/PANI, AlZnO/PANI. This research is innovative with respect to low cost synthesis of efficient and sensitive hybrid p–n junction diodes and possibly serves as the building blocks for future optoelec- tronic applications. Keywords Metal doped ZnO nanorods Á Polyaniline Á Ideality factor Á Barrier height Á Hybrid p–n junction 1 Introduction Hybrid inorganic/organic heterojunction devices have received much attention as promising junctions for wide- spread applications. There are reports available on the use of these heterojunctions as gas sensors, light emitting diodes, photo detectors and solar cells [1–4]. Transparent conducting oxide (TCO) serves as the inorganic semicon- ductor in these heterojunctions. Zinc oxide (ZnO) is one of such famous transparent conducting oxides [5]. ZnO, especially in its nanostructured form, has been considered to be attractive because of the wide band gap (3.4 eV) and high exciton binding energy (60 meV). However, it is difficult to fabricate ZnO with stable p-type conductivity because of its intrinsically n-type nature. The n-type behavior is typically because of the interstitial defects and oxygen vacancies in ZnO wurtzite structure. The difficulty in doping ZnO to p-type impurity has led the researchers to prepare the heterojunctions with other p-type semicon- ductors for its use in various electronic devices [6]. The quality of p–n heterojunction is mainly limited by the lat- tice mismatch. This difficulty gets resolved by using ZnO nanostructures. The nanostructures of ZnO possess self organized growth property which enables easy growth of p type material over n type material thus producing hetero- junctions of quality devices by using external p-type materials [7]. In addition, ZnO nanorods provide large surface area which is useful for the heterojunction forma- tion. ZnO/organic hybrid structure has found importance in solar cell, photodiodes, photovoltaic and photochemical applications. The electrical conductivity of ZnO can be increased by adding a small amount of impurity(doping) e.g. alkali metals like B, Li [8] or metals like Al [9], Fe [10, 11], Cu [12], Ni [13], Co [14] and Ga [15, 16] etc. There are reports available for higher values of conductivities & Sushama M. Giripunje smgiripunje@phy.vnit.ac.in 1 Department of Applied Physics, Priyadarshini College of Engineering, Nagpur 440018, India 2 Department of Applied Physics, Visvesvaraya National Institute of Technology, Nagpur 440010, India 3 Department of Physics, Rashtrasant Tukadoji Maharaj Nagpur University, Nagpur 440033, India 123 J Inorg Organomet Polym (2016) 26:370–375 DOI 10.1007/s10904-016-0333-7