Thesis Title: "Redefining Design Principles in Low-Dimensional Perovskite Solar Cells: 
Perovskite Bulk, Interfaces, and Charge Extraction Dynamics"

Name of the Student: Ms. Bhumika Sharma

Degree Registered: Ph.D. Engineering 

Advisor: Prof. Sushobhan Avasthi, CeNSE

Date: 10th April 2026, (Friday), 4 PM

Venue: CeNSE Seminar Hall (Hybrid)

Abstract:

Low-dimensional perovskites exhibit enhanced stability against oxygen and moisture in comparison
 to their three-dimensional counterparts, but it comes at the expense of efficiency. Several 
attempts such as additive engineering, compositional engineering, and the addition of interlayers 
to improve the efficiency have been made but understanding the fundamental differences and their 
impact on devices remain incomplete. This thesis aims to re-define the design principles of 
low-dimensional perovskite solar cells by investigating techniques which can be directly translated 
from three dimensional solar cells and identifying and amending the ones which need re-optimization. 
The properties of perovskite bulk, the hole transport layers (HTLs), and the interface between them 
is studied while paying attention to the optoelectronic processes that govern device performance.

We begin by examining the role of interfacial engineering by using ionic liquid to passivate perovskite,
 without changing its bulk. This interlayer enhances carrier lifetime by suppressing non radiative 
recombination, which results in improved performance for low-dimensional solar cells. Another work 
which discusses the effect of interlayer uses self-assembled monolayer (SAM) as an HTL, which are known 
to suffer from wettability issues. A seed layer of phenethylammonium iodide increases the wettability 
of SAM and its impact on the growth of low-dimensional perovskites is studied. The study reveals that 
changes in nucleation and growth of perovskites influences morphology, strain, and bulk quality of perovskite. 
The addition of interlayers either results in passivation or improves the perovskite bulk, both of which 
can be translated from three- to low-dimensional systems.

Building on this, the role of HTL is evaluated by using NiO𝑥 deposited via pulsed DC magnetron sputtering. 
The NiO𝑥 optimized for three-dimensional perovskite results in inferior performance to the one specifically 
optimized for low-dimensional perovskite. The need for re optimization of transport layers is hence highlighted 
to elucidate the complete potential of low dimensional perovskites. The thesis further discusses the importance
 of intermediate size distribution in perovskite precursors in governing the growth dynamics of thin films. The 
intermediate size distribution is altered by redissolving perovskite powder prepared by inverse temperature 
crystallization to form a precursor. The powder-processed precursor shows less viscosity and smaller intermediates 
leading to higher growth rates. This enhances carrier lifetime and perovskite bulk quality, leading to devices 
having better efficiency and stability.

In conclusion, this thesis establishes that moving beyond empirical optimizations and focusing on the fundamental
 mechanisms is essential to improve the quality and reproducibility of low dimensional solar cells. With careful 
consideration of optoelectronic properties of perovskite, the electrically coupled transport layers, and interfaces, 
the design strategies can be modified to enhance the performance of low-dimensional cells to their true potential.