Interfacial Engineering of a TiO₂ Photoanode via Graphene Nanoribbons for Efficient Quantum-Dot-Sensitized Solar Cells and Photoelectrochemical Water Splitting

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.