Enhancing stability and efficiency in SnO2 based HTL-free, printable carbon-based perovskite solar cells for outdoor/indoor photovoltaics

Abstract

Recent advancements in hole transport layer (HTL)-free, printable carbon-based perovskite solar cells (C-PSCs) have gained increased research interest. Notably, their scalability, cost-effectiveness, and improved stability make them particularly attractive among various perovskite solar cell configurations. In the current study, we explored the potential of un-encapsulated, HTL-free, C-PSCs in outdoor and indoor light conditions, employing different concentrations of tin oxide (SnO₂) as the electron transport material. Among the investigated concentrations, 0.07 M SnO₂ precursor yielded the highest power conversion efficiency (PCE), reaching 9.79% under standard 1 sun illumination and 10.40% at a lower intensity of 0.6 sun. The PSCs demonstrated a remarkable 22.37% efficiency under 1000 lx indoor CFL illumination, and attained 22.21% efficiency under LED illumination, marking the highest reported indoor photovoltaic performance for carbon-based, HTL-free PSCs. To elucidate the underlying charge-transfer process, we carried out intensity-dependent current−voltage (J-V) measurements to analyze non-radiative bulk recombination in the perovskite layer. Interfacial recombination was investigated using electrochemical impedance spectroscopy (EIS) and transient photovoltage decay measurements. Optical and electrical stimulation of C-PSCs were performed under both full sun and indoor illumination, providing insight into recombination and light absorption differences under these illuminations. Additionally, we also showcased the potential of simple, printable indoor light harvesters for self-powered applications by connecting two C-PSCs to create a self-powered temperature sensor.