Enhanced perovskite solar cells with TiO2-Graphene nanocomposite quantum dots in electron transport layer

Perovskite Solar Cells (PSCs) have emerged as a promising platform for clean energy harvesting, thanks to their cost-effectiveness and low-temperature fabrication requirements. However, their widespread adoption is hindered by challenges such as charge trapping, and instability when exposed to UV light and humidity, preventing PSCs from becoming mainstream in solar cell production. PSCs consist of a perovskite (PSK) layer sandwiched between an electron transport layer (ETL) and a hole transport layer (HTL). Although TiO2 is widely used as the ETL due to its suitable band alignment, it suffers from low carrier mobility, poor stability under UV light, and thermal losses due to hot electron transfer. In this study, we enhance the ETL by incorporating Graphene Quantum Dots (GQDs) into a nanocomposite with TiO2 Quantum Dots, creating an interface between the mesoporous TiO2 and the PSK layer. This approach aims to improve charge transfer and reduce trapped states in PSCs via a one-step coating process. The TiO2-GQDs nanocomposite quantum dots were synthesized via an electrochemical process and doped with titanium tetraisopropoxide (TTIP) at a concentration of 7.5 % w/w to create the ETL with the nanocomposite QDs interface. Our results demonstrate significant improvements in power conversion efficiency (PCE), fill factor (FF), short-circuit current density, and open-circuit voltage, along with a reduction in recombination rates, trap charge density, and charge transfer resistance. Notably, the PCE of devices with ETL modified by our nanocomposite QDs increased from 12.0 % in the control device to 15.1 %. The simplicity of our one-step coating process for TiO2-GQDs nanocomposite quantum dots in colloidal form further supports the scalability and industrial viability of this method for PSC production.