Interfacial Engineering of a TiO<sub>2</sub> Photoanode via Graphene Nanoribbons for Efficient Quantum-Dot-Sensitized Solar Cells and Photoelectrochemical Water Splitting
Iqbal Singh, Viplove Bhullar, Aman Mahajan
Abstract
Quantum dot (QD)-sensitized TiO 2 photoanodes are a common component of quantum dot-sensitized solar cells (QDSSCs) and photoelectrochemical (PEC) water-splitting applications. The QD-sensitized TiO 2 photoanode harvested energy from sunlight and then produced electric energy and clean H 2 fuel by QDSSCs and PEC water-splitting devices, respectively. Despite various interfacial modifications, such photoanode still suffers from numerous recombinations and poor electron transport, degrading the performance of devices. In the present work, highly conductive one-dimensional (1D) graphene nanoribbons (GNRs) have been incorporated in both TiO 2 -based compact as well as mesoporous (m-TiO 2 ) layers to reduce recombinations and achieve a superior charge transport network. Initially, the content of GNR has been optimized in a compact layer, and the maximum power conversion efficiency (PCE) in QDSSCs and photocurrent density in PEC water splitting have been attained around 2.33% and 1.92 mA cm –2, respectively. Furthermore, incorporation of GNR in the m-TiO 2 layer delivered enhanced short-circuit current density and better electron transport in both QDSSCs and PEC water splitting. The optimized device showed 3.06% PCE for QDSSCs and 2.39 mA cm –2 photocurrent density for PEC water splitting. After that, the optimized concentrations of GNR from both cases have been used to prepare devices that give 113 and 80% enhancement in PCE and photocurrent density in QDSSCs and PEC water splitting, respectively. Moreover, an improvement in PCE of QDSSCs to 4.55% and photocurrent density of the PEC water-splitting device of 2.67 mA cm –2 has been recorded with co-sensitization of the optimized photoanode.