Opportunities

Photovoltaic devices convert light to electricity. Indoor photovoltaic (IPVs) devices convert light from artificial light sources such as white LED and fluorescent lamps inside the buildings to electrical energy. IPVs are receiving great research attention recently due to its projected application in the huge technology field of Internet of Things (IoT). IoT is a smart network of connected physical objects embedded with sensors and actuators. Wireless sensors, requiring only μW-mW for their efficient functioning, are the most fundamental components in these smart devices. By 2025, there will be more than 75 billion connected IoT devices with half of the components to be installed inside the buildings. Sustainably powering these sensors is a huge challenge. Powering these billions of sensors by grid connected electricity, or by batteries is not a feasible solution and limits the IoT potential. Light energy is available in the ambient environment and can be accessed easily via photovoltaic devices without requesting additional devices or multiple energy transfer, thus becomes the most promising candidate to power IoT sensor system [1].

The Shockley-Queisser (S-Q) limit of power conversion efficiency of indoor photovoltaic is 45-65% depending on the input light spectrum (white LED or CFL) [2]. So far, the highest reported power conversion efficiency for halide perovskite indoor photovoltaic is 36%. One of the main limiting factors in achieving the theoretical efficiency is the high open-circuit voltage (V_oc) losses. V_oc depends on the splitting of the quasi-fermi level upon the light absorption by the photovoltaic material. Since the intensity of indoor light sources is 100 times lower than that of outdoor solar spectra, to maximise the power conversion efficiency, stringent carrier management and prevention of recombination losses is essential [3].
In this project, we will investigate the role of interface engineering to minimize these open-circuit voltages in halide perovskite indoor photovoltaic devices. Both the bulk interface in the photoactive materials and the buried interface at the photoactive layer/charge-transporting layers will be studied. The photogenerated carrier dynamics will be characterised using transient photovoltaic measurements such as transient current, transient photovoltage, and mobility of these carriers will be investigated through space charge limited current method and interface role will be isolated from the bulk using the impedance spectroscopy of the photovoltaic devices.

[1] Müller et al IEEE J. Photovoltaics (2013) 3 59
[2] Peters et al Joule (2019) 3 P1415
[3] Jagadamma et al Sol. Energy Mater. Sol. Cells (2019) 201 110071