Abstract

Photovoltaic solar cell is one of the most important renewable energy sources, which can supply
required energy to various electronic devices as well as enormous energy to power grids. Among
various photovoltaic devices, thin-film solar cells provide high power conversion efficiency at
lower production cost. Though they provide reasonably high efficiency, there is possibility to
improve the efficiency further through properly understanding the efficiency limiting factors. To
achieve this goal, a physics-based compact analytical model for studying the carrier distribution
and resultant photocurrent alongside with the current-voltage (J-V) characteristics of bulk
heterojunction (BHJ) perovskite solar cells (PSC) has been proposed in this thesis by considering
exponential photon absorption profile, bulk and surface recombination, and carrier drift &
diffusion in the photon absorption layer.
By solving the continuity equation for both electrons and holes in the perovskite layer, it is possible
to construct an analytical formula for the position-dependent carrier concentration and associated
external voltage-dependent photocurrent. The position dependent total conduction current (sum of
the drift and diffusion currents of both holes and electrons) under steady-state is found to be space
invariant which is exactly equal to the total photocurrent calculated using the Shockley-Ramo's
theorem. The calculation of the total load current considers the actual solar spectrum, photocurrent
and voltage-dependent forward dark current. The mathematical model is fitted with experimental
results of various perovskite solar cells and useful physical transport parameters are extracted by
comparing the model calculations with the published experimental data. The effects of
recombination on the photocurrent and overall efficiency are analysed quantitatively. The charge
carrier transport parameters, especially the surface recombination velocity, have very significant
effects on the current-voltage characteristics and power conversion efficiency.